No Evidence of Uptake or Propagation of Reindeer CWD Prions in Environmentally Exposed Sheep?
RESEARCH ARTICLE
No Evidence of Uptake or Propagation of Reindeer CWD Prions in Environmentally Exposed Sheep
Erez Harpaz, Cecilie Ersdal, Michael Tranulis, Arild Espenes, Øyvind Salvesen, Aqsa Mahmood, Geir Rune Rauset, Bjørnar Ytrehus, Sylvie Benestad, Linh Tran
DOI: 10.21203/rs.3.rs-923104/v1
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Abstract
Background: Chronic wasting disease (CWD) is a prion disease of cervids. In 2016, CWD was discovered for the first time in reindeer. The affected population was situated in Nordfjella mountain region in Norway. In an attempt to eradicate the disease, all reindeer in the region were culled during winter 2017-18. Because many sheep have their summer pasture in Nordfjella, concern exists about the potential cross-species transmission of CWD to sheep. In this study, global positioning system (GPS) data from sheep and reindeer from the relevant time frame were analyzed to determine spatial overlap. Samples of gut-associated lymphoid tissue (GALT) from 503 lambs and sheep having grazed in the region were analyzed for the presence of prions. The rectoanal mucosa-associated lymphoid tissue (RAMALT) from all animals and ileal Peyer's patch (IPP) from 37 of them, were examined by histology, immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA).
Results: GPS data showed a direct overlap in area use between an infected reindeer and some of the sampled sheep. Generally, the sampled sheep herding areas were used intensively by reindeer before culling. No prions were detected in the GALT of sheep. The mean lymphoid follicle number per sample was 22.6 for RAMALT and 37.5 for IPP.
Conclusion: Despite evidence of close reindeer to sheep interaction and spatial overlap in Nordfjella, prions were not detected in the GALT of sheep.. We document that the easily accessible RAMALT tissue at the mucocutaneous border is well suitable for slaughterhouse screening of prions in sheep.
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Conclusion
Despite evidence of close interaction and spatial overlap between reindeer and sheep in Nordfjella zone 1, we did not find any evidence of uptake and propagation of prions by sheep that were very likely exposed to environmental CWD prions. We conclude that RAMALT is a suitable tissue for postmortem mass sampling, and although it yields on average fewer lymphoid follicles than the IPP per sample, the ease and speed of sampling makes it a better choice. We also showed that using the mucocutaneous junction as a guideline for sampling increases the mean number of lymphoid follicles in the sample, and hence reduces the probability of false-negative results. This study was not aimed to determine whether CWD is transmissible to sheep. For that, long-term inoculation studies are needed. Still, the absence of prions from sheep RAMALT and IPP indicates that CWD prion uptake and propagation by sheep under the environmental conditions that exist in Nordfjella, is not prevalent.
***> CONGRESSIONAL ABSTRACTS PRION CONFERENCE 2018
P69 Experimental transmission of CWD from white-tailed deer to co-housed reindeer
Mitchell G (1), Walther I (1), Staskevicius A (1), Soutyrine A (1), Balachandran A (1)
(1) National & OIE Reference Laboratory for Scrapie and CWD, Canadian Food Inspection Agency, Ottawa, Ontario, Canada.
Chronic wasting disease (CWD) continues to be detected in wild and farmed cervid populations of North America, affecting predominantly white-tailed deer, mule deer and elk. Extensive herds of wild caribou exist in northern regions of Canada, although surveillance has not detected the presence of CWD in this population. Oral experimental transmission has demonstrated that reindeer, a species closely related to caribou, are susceptible to CWD. Recently, CWD was detected for the first time in Europe, in wild Norwegian reindeer, advancing the possibility that caribou in North America could also become infected. Given the potential overlap in habitat between wild CWD-infected cervids and wild caribou herds in Canada, we sought to investigate the horizontal transmissibility of CWD from white-tailed deer to reindeer.
Two white-tailed deer were orally inoculated with a brain homogenate prepared from a farmed Canadian white-tailed deer previously diagnosed with CWD. Two reindeer, with no history of exposure to CWD, were housed in the same enclosure as the white-tailed deer, 3.5 months after the deer were orally inoculated. The white-tailed deer developed clinical signs consistent with CWD beginning at 15.2 and 21 months post-inoculation (mpi), and were euthanized at 18.7 and 23.1 mpi, respectively. Confirmatory testing by immunohistochemistry (IHC) and western blot demonstrated widespread aggregates of pathological prion protein (PrPCWD) in the central nervous system and lymphoid tissues of both inoculated white-tailed deer. Both reindeer were subjected to recto-anal mucosal associated lymphoid tissue (RAMALT) biopsy at 20 months post-exposure (mpe) to the white-tailed deer. The biopsy from one reindeer contained PrPCWD confirmed by IHC. This reindeer displayed only subtle clinical evidence of disease prior to a rapid decline in condition requiring euthanasia at 22.5 mpe. Analysis of tissues from this reindeer by IHC revealed widespread PrPCWD deposition, predominantly in central nervous system and lymphoreticular tissues. Western blot molecular profiles were similar between both orally inoculated white-tailed deer and the CWD positive reindeer. Despite sharing the same enclosure, the other reindeer was RAMALT negative at 20 mpe, and PrPCWD was not detected in brainstem and lymphoid tissues following necropsy at 35 mpe. Sequencing of the prion protein gene from both reindeer revealed differences at several codons, which may have influenced susceptibility to infection.
Natural transmission of CWD occurs relatively efficiently amongst cervids, supporting the expanding geographic distribution of disease and the potential for transmission to previously naive populations. The efficient horizontal transmission of CWD from white-tailed deer to reindeer observed here highlights the potential for reindeer to become infected if exposed to other cervids or environments infected with CWD.
SOURCE REFERENCE 2018 PRION CONFERENCE ABSTRACT
Research Project: TRANSMISSION, DIFFERENTIATION, AND PATHOBIOLOGY OF TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES Location: Virus and Prion Research
Title: Horizontal transmission of chronic wasting disease in reindeer
Author
item MOORE, SARAH - ORISE FELLOW item KUNKLE, ROBERT item WEST GREENLEE, MARY - IOWA STATE UNIVERSITY item Nicholson, Eric item RICHT, JUERGEN item HAMIR, AMIRALI item WATERS, WADE item Greenlee, Justin
Submitted to: Emerging Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2016
Publication Date: 12/1/2016
Citation: Moore, S., Kunkle, R., Greenlee, M., Nicholson, E., Richt, J., Hamir, A., Waters, W., Greenlee, J. 2016. Horizontal transmission of chronic wasting disease in reindeer. Emerging Infectious Diseases. 22(12):2142-2145. doi:10.3201/eid2212.160635.
Interpretive Summary: Chronic wasting disease (CWD) is a fatal neurodegenerative disease that occurs in farmed and wild cervids (deer and elk) of North America and was recently diagnosed in a single free-ranging reindeer (Rangifer tarandus tarandus) in Norway. CWD is a transmissible spongiform encephalopathy (TSE) that is caused by infectious proteins called prions that are resistant to various methods of decontamination and environmental degradation. Little is known about the susceptibility of or potential for transmission amongst reindeer. In this experiment, we tested the susceptibility of reindeer to CWD from various sources (elk, mule deer, or white-tailed deer) after intracranial inoculation and tested the potential for infected reindeer to transmit to non-inoculated animals by co-housing or housing in adjacent pens. Reindeer were susceptible to CWD from elk, mule deer, or white-tailed deer sources after experimental inoculation. Most importantly, non-inoculated reindeer that were co-housed with infected reindeer or housed in pens adjacent to infected reindeer but without the potential for nose-to-nose contact also developed evidence of CWD infection. This is a major new finding that may have a great impact on the recently diagnosed case of CWD in the only remaining free-ranging reindeer population in Europe as our findings imply that horizontal transmission to other reindeer within that herd has already occurred. Further, this information will help regulatory and wildlife officials developing plans to reduce or eliminate CWD and cervid farmers that want to ensure that their herd remains CWD-free, but were previously unsure of the potential for reindeer to transmit CWD.
Technical Abstract: Chronic wasting disease (CWD) is a naturally-occurring, fatal prion disease of cervids. Reindeer (Rangifer tarandus tarandus) are susceptible to CWD following oral challenge, and CWD was recently reported in a free-ranging reindeer of Norway. Potential contact between CWD-affected cervids and Rangifer species that are free-ranging or co-housed on farms presents a potential risk of CWD transmission. The aims of this study were to 1) investigate the transmission of CWD from white-tailed deer (Odocoileus virginianus; CWDwtd), mule deer (Odocoileus hemionus; CWDmd), or elk (Cervus elaphus nelsoni; CWDelk) to reindeer via the intracranial route, and 2) to assess for direct and indirect horizontal transmission to non-inoculated sentinels. Three groups of 5 reindeer fawns were challenged intracranially with CWDwtd, CWDmd, or CWDelk. Two years after challenge of inoculated reindeer, non-inoculated negative control reindeer were introduced into the same pen as the CWDwtd inoculated reindeer (direct contact; n=4) or into a pen adjacent to the CWDmd inoculated reindeer (indirect contact; n=2). Experimentally inoculated reindeer were allowed to develop clinical disease. At death/euthanasia a complete necropsy examination was performed, including immunohistochemical testing of tissues for disease-associated CWD prion protein (PrPcwd). Intracranially challenged reindeer developed clinical disease from 21 months post-inoculation (months PI). PrPcwd was detected in 5 out of 6 sentinel reindeer although only 2 out of 6 developed clinical disease during the study period (< 57 months PI). We have shown that reindeer are susceptible to CWD from various cervid sources and can transmit CWD to naïve reindeer both directly and indirectly.
>>>Given the results of this study, current diagnostic techniques would be unlikely to distinguish CWD in sheep from scrapie in sheep if cross-species transmission occurred naturally. It is unknown if sheep are naturally vulnerable to CWD; however, the susceptibility of sheep after intracranial inoculation and lymphoid accumulation indicates that the species barrier is not absolute.<<<
Second passage of chronic wasting disease of mule deer in sheep compared to classical scrapie after intracranial inoculation
Research Project: Pathobiology, Genetics, and Detection of Transmissible Spongiform Encephalopathies Location: Virus and Prion Research
Title: Second passage of chronic wasting disease of mule deer in sheep compared to classical scrapie after intracranial inoculation
Author item Cassmann, Eric item FRESE, RYLIE - Orise Fellow item Greenlee, Justin Submitted to: Journal of Veterinary Diagnostic Investigation Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/25/2020 Publication Date: N/A Citation: N/A
Interpretive Summary: Chronic wasting disease (CWD) is a fatal and uncurable brain disease of deer and elk that is related to a similar disease in sheep called scrapie. Both diseases are cause by a misfolded protein called a prion. The exact origin of CWD is unknown, but a possible origin could have been spread of sheep scrapie to deer. Previous research found indistinguishable traits in common between CWD in deer and scrapie in sheep. Additionally, it is unknown if deer CWD can naturally transmit to sheep. In this research, we show that abnormal prions spread throughout the body of sheep intracranially infected with CWD similar to how scrapie spreads in sheep. We compared two US classical scrapie strains to CWD in sheep and found that one of these strains is indistinguishable from sheep CWD. These results demonstrate that current diagnostic techniques would be unlikely to distinguish CWD in sheep from scrapie in sheep if cross-species transmission occurred in a natural setting. This research reinforces the need to continue ongoing cross-species transmission studies focusing on oral susceptibility of sheep to CWD and develop techniques to discriminate sheep CWD from sheep scrapie.
Technical Abstract: The origin of chronic wasting disease (CWD) in cervids is unclear. One hypothesis suggests that CWD originated from scrapie in sheep. In this experiment, we had two main objectives. The first objective was to determine if CWD adaptation in sheep alters the disease phenotype. The second objective was to determine if the disease phenotype of sheep adapted CWD is distinct from classical scrapie. We intracranially inoculated sheep with brain homogenate from first passage mule deer CWD in sheep (sCWDmd). The attack rate in second passage sheep was 100% (12/12). Sheep had prominent lymphoid accumulations of PrPSc reminiscent of classical scrapie. The pattern and distribution of PrPSc in the brains of sheep with CWDmd was similar to scrapie strain 13-7 but different from scrapie strain x124. The western blot glycoprofiles of sCWDmd were indistinguishable from scrapie strain 13-7; however, independent of sheep genotype, glycoprofiles of sCWDmd were different than x124. When sheep genotypes were evaluated individually, there was considerable overlap in the glycoprofiles that precluded significant discrimination between sheep CWD and scrapie strains. Taken together, these data suggest that the phenotype of CWD in sheep is indistinguishable from some strains of scrapie in sheep. Given the results of this study, current diagnostic techniques would be unlikely to distinguish CWD in sheep from scrapie in sheep if cross-species transmission occurred naturally. It is unknown if sheep are naturally vulnerable to CWD; however, the susceptibility of sheep after intracranial inoculation and lymphoid accumulation indicates that the species barrier is not absolute.
>>>Given the results of this study, current diagnostic techniques would be unlikely to distinguish CWD in sheep from scrapie in sheep if cross-species transmission occurred naturally. It is unknown if sheep are naturally vulnerable to CWD; however, the susceptibility of sheep after intracranial inoculation and lymphoid accumulation indicates that the species barrier is not absolute.<<<
1. Interspecies transmission of the chronic wasting disease agent
Justin Greenlee
Virus and Prion Research Unit, National Animal Disease Center, USDA Agriculture Research Service
ABSTRACT
The presentation will summarize the results of various studies conducted at our research center that assess the transmissibility of the chronic wasting disease (CWD) agent to cattle, pigs, raccoons, goats, and sheep. This will include specifics of the relative attack rates, clinical signs, and microscopic lesions with emphasis on how to differentiate cross-species transmission of the CWD agent from the prion diseases that naturally occur in hosts such as cattle or sheep. Briefly, the relative difficulty of transmitting the CWD agent to sheep and goats will be contrasted with the relative ease of transmitting the scrapie agent to white-tailed deer.
>>>However, WTD scrapie efficiently transmitted back to sheep by the oronasal route. Upon transmission back to sheep, the WTD scrapie isolate exhibited different phenotypic properties when compared to the sheep receiving the original sheep scrapie inoculum including different genotype susceptibilities, distinct PrPSc deposition patterns, and much more rapid incubation periods in transgenic mice expressing the ovine prion protein. The scrapie agent readily transmits between sheep and deer after oronasal exposure. This could confound the identification of CWD strains in deer and the eradication of scrapie from sheep.<<<
223. Scrapie in white-tailed deer: a strain of the CWD agent that efficiently transmits to sheep?
Justin J. Greenleea, Robyn D. Kokemullera, S. Jo Moorea and Heather West Greenleeb
aVirus and Prion Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, Ames, IA, USA; bDepartment of Biomedical Sciences, Iowa State University College of Veterinary Medicine, Ames, IA, USA
CONTACT Justin J. Greenlee Justin.Greenlee@ars.usda.gov
ABSTRACT
Scrapie is a transmissible spongiform encephalopathy of sheep and goats that is associated with widespread accumulation of abnormal prion protein (PrPSc) in the central nervous and lymphoid tissues. Chronic wasting disease (CWD) is the natural prion disease of cervid species, and the tissue distribution of PrPSc in affected cervids is similar to scrapie in sheep. There are several lines of evidence that suggest that multiple strains of CWD exist, which may affect the agent’s potential to transmit to hosts of the same or different species. We inoculated white-tailed deer with the scrapie agent from ARQ/ARQ sheep, which resulted in 100% attack rates by either the intracranial or oronasal route of inoculation. When examining tissues from the brainstems or lymphoid tissues by traditional diagnostic methods such as immunohistochemistry or western blots, it is difficult to differentiate tissues from deer infected with scrapie from those infected with CWD. However, there are several important differences between tissues from scrapie-infected white-tailed deer (WTD scrapie) and those infected with CWD (WTD CWD). First, there are different patterns of PrPSc deposition in the brains of infected deer: brain tissues from deer with WTD scrapie had predominantly particulate and stellate immunoreactivity whereas those from deer with WTD-CWD had large aggregates and plaque-like deposits. Secondly, the incubation periods of WTD scrapie isolates are longer than CWD isolates in mice expressing cervid prion protein. Most notably, the transmission potential of these two isolates back to sheep is distinctly different. Attempts to transmit various CWD isolates to sheep by the oral or oronasal routes have been unsuccessful despite observation periods of up to 7 years. However, WTD scrapie efficiently transmitted back to sheep by the oronasal route. Upon transmission back to sheep, the WTD scrapie isolate exhibited different phenotypic properties when compared to the sheep receiving the original sheep scrapie inoculum including different genotype susceptibilities, distinct PrPSc deposition patterns, and much more rapid incubation periods in transgenic mice expressing the ovine prion protein. The scrapie agent readily transmits between sheep and deer after oronasal exposure. This could confound the identification of CWD strains in deer and the eradication of scrapie from sheep.
Research Project: Pathobiology, Genetics, and Detection of Transmissible Spongiform Encephalopathies Location: Virus and Prion Research
Title: Scrapie in white-tailed deer: a strain of the CWD agent that efficiently transmits to sheep?
Author item Greenlee, Justin item KOKEMULLER, ROBYN - US Department Of Agriculture (USDA) item MOORE, S - Oak Ridge Institute For Science And Education (ORISE) item WEST GREENLEE, M - Iowa State University
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/29/2019
Publication Date: N/A
Citation: N/A
Interpretive Summary:
Technical Abstract: Scrapie is a transmissible spongiform encephalopathy of sheep and goats that is associated with widespread accumulation of abnormal prion protein (PrPSc) in the central nervous and lymphoid tissues. Chronic wasting disease (CWD) is the natural prion disease of cervid species, and the tissue distribution of PrPSc in affected cervids is similar to scrapie in sheep. There are several lines of evidence that suggest that multiple strains of CWD exist, which may affect the agent’s potential to transmit to hosts of the same or different species. We inoculated white-tailed deer with the scrapie agent from ARQ/ARQ sheep, which resulted in 100% attack rates by either the intracranial or oronasal route of inoculation. When examining tissues from the brainstems or lymphoid tissues by traditional diagnostic methods such as immunohistochemistry or western blots, it is difficult to differentiate tissues from deer infected with scrapie from those infected with CWD. However, there are several important differences between tissues from scrapie-infected white-tailed deer (WTD scrapie) and those infected with CWD (WTD CWD). First, there are different patterns of PrPSc deposition in the brains of infected deer: brain tissues from deer with WTD scrapie had predominantly particulate and stellate immunoreactivity whereas those from deer with WTD-CWD had large aggregates and plaque-like staining. Secondly, the incubation periods of WTD scrapie isolates are longer than CWD isolates in mice expressing cervid prion protein. Most notably, the transmission potential of these two isolates back to sheep is distinctly different. Attempts to transmit various CWD isolates to sheep by the oral or oronasal routes have been unsuccessful despite observation periods of up to 7 years. However, WTD scrapie efficiently transmitted back to sheep by the oronasal route. Upon transmission back to sheep, the WTD scrapie isolate exhibited different phenotypic properties when compared to the sheep receiving the original sheep scrapie inoculum including different genotype susceptibilities, distinct PrPSc deposition patterns, and much more rapid incubation periods in transgenic mice expressing the ovine prion protein. The scrapie agent readily transmits between sheep and deer after oronasal exposure. This could confound the identication of CWD strains in deer and the eradication of scrapie from sheep.
Research Project: Pathobiology, Genetics, and Detection of Transmissible Spongiform Encephalopathies Location: Virus and Prion Research
Title: Passage of scrapie to deer results in a new phenotype upon return passage to sheep
Author item Greenlee, Justin item Kokemuller, Robyn item MOORE, SARAH - Orise Fellow
item WEST GREENLEE, N - Iowa State University
Submitted to: Prion Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2017
Publication Date: N/A
Citation: N/A
Interpretive Summary:
Technical Abstract: Aims: We previously demonstrated that scrapie has a 100% attack rate in white-tailed deer after either intracranial or oral inoculation. Samples from deer that developed scrapie had two different western blot patterns: samples derived from cerebrum had a banding pattern similar to the scrapie inoculum, but samples from brainstem had a banding pattern similar to CWD. In contrast, transmission of CWD from white-tailed deer to sheep by the intracranial route has a low attack rate and to-date oronasal exposure has been unsuccessful. The purpose of this study was to determine if sheep are susceptible to oronasal exposure of the scrapie agent derived from white-tailed deer. Methods: At approximately 5 months of age, Suffolk sheep of various PRNP genotypes were challenged by the oronasal route with 10% brain homogenate derived from either the cerebrum or the brainstem of scrapie-affected deer. Genotypes represented in each inoculation group were VV136RR154QQ171 (n=2), AA136RR154QQ171 (n=2), and AV136RR154QR171 (n=1). After inoculation, sheep were observed daily for clinical signs. Upon development of clinical signs, sheep were killed with an overdose of pentobarbital sodium and necropsied. Tissue samples were tested for the presence of PrPSc by EIA, western blot, and immunohistochemistry (IHC). The No. 13-7 scrapie inoculum used for the deer has a mean incubation period of 20.1 months in sheep with the AA136RR154QQ171 genotype and 26.7 months in sheep with the VV136RR154QQ171 genotype. Results: Sheep inoculated oronasally with WTD derived scrapie developed disease, but only after inoculation with the inoculum from the cerebrum that had a scrapie-like profile. The first sheep to develop clinical signs at approximately 29 months post inoculation had the VV136RR154QQ171 genotype. Eventually sheep of the AA136RR154QQ171 genotype developed clinical signs, but at a mean incubation of 52 months. At 62 months post-inoculation, none of the sheep inoculated with material from the deer brainstem have developed clinical disease. Conclusions: The No. 13-7 inoculum used in the original deer experiment readily infects white-tailed deer and sheep of various genotypes by the oronasal route. When inoculum is made from different brain regions of No 13-7 scrapie-infected deer from either cerebrum with a scrapie-like western blot pattern or brainstem with a CWD-like western blot pattern, sheep with the VV136RR154QQ171 genotype are the first to develop clinical signs. This is in contrast to the original No. 13-7 inoculum that has a faster incubation period in sheep with the AA136RR154QQ171 genotype. Similar to experiments conducted with CWD, sheep oronasally inoculated with brainstem material from deer with a CWD-like molecular profile have no evidence of disease after 62 months of incubation. While scrapie is not known to occur in free-ranging populations of white-tailed deer, experimental cases are difficult to differentiate from CWD. This work raises the potential concern that scrapie infected deer could serve as a confounding factor to scrapie eradication programs as scrapie from deer seems to be transmissible to sheep by the oronasal route.
Title: Scrapie transmits to white-tailed deer by the oral route and has a molecular profile similar to chronic wasting disease
Author item Greenlee, Justin item MOORE, S - Orise Fellow item SMITH, JODI - Iowa State University item Kunkle, Robert item WEST GREENLEE, M - Iowa State University
Submitted to: American College of Veterinary Pathologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/12/2015
Publication Date: N/A
Citation: N/A
Interpretive Summary:
Technical Abstract: The purpose of this work was to determine susceptibility of white-tailed deer (WTD) to the agent of sheep scrapie and to compare the resultant PrPSc to that of the original inoculum and chronic wasting disease (CWD). We inoculated WTD by a natural route of exposure (concurrent oral and intranasal (IN); n=5) with a US scrapie isolate. All scrapie-inoculated deer had evidence of PrPSc accumulation. PrPSc was detected in lymphoid tissues at preclinical time points, and deer necropsied after 28 months post-inoculation had clinical signs, spongiform encephalopathy, and widespread distribution of PrPSc in neural and lymphoid tissues. Western blotting (WB) revealed PrPSc with 2 distinct molecular profiles. WB on cerebral cortex had a profile similar to the original scrapie inoculum, whereas WB of brainstem, cerebellum, or lymph nodes revealed PrPSc with a higher profile resembling CWD. Homogenates with the 2 distinct profiles from WTD with clinical scrapie were further passaged to mice expressing cervid prion protein and intranasally to sheep and WTD. In cervidized mice, the two inocula have distinct incubation times. Sheep inoculated intranasally with WTD derived scrapie developed disease, but only after inoculation with the inoculum that had a scrapie-like profile. The WTD study is ongoing, but deer in both inoculation groups are positive for PrPSc by rectal mucosal biopsy. In summary, this work demonstrates that WTD are susceptible to the agent of scrapie, two distinct molecular profiles of PrPSc are present in the tissues of affected deer, and inoculum of either profile readily passes to deer.
Title: White-Tailed Deer Susceptible to Scrapie by Natural Route of Infection
Author item Greenlee, Justin item Smith, Jodi item Kunkle, Robert
Submitted to: American College of Veterinary Pathologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/30/2010
Publication Date: 10/30/2010
Citation: Greenlee, J.J., Smith, J.D., Kunkle, R.A. 2010. White-tailed deer susceptible to scrapie by natural route of infection [abstract]. American College of Veterinary Pathologists. Paper No. 81.
Interpretive Summary:
Technical Abstract: Interspecies transmission studies afford the opportunity to better understand the potential host range and origins of prion diseases. Previous experiments demonstrated that white-tailed deer are susceptible to sheep-derived scrapie by intracranial inoculation. The purpose of an ongoing study is to determine susceptibility of white-tailed deer to scrapie after a natural route of exposure. Deer (n=5) were inoculated by concurrent oral (30 ml) and intranasal (1 ml) instillation of a 10% (wt/vol) brain homogenate derived from a sheep clinically affected with scrapie. Non-inoculated deer were maintained as negative controls. All deer are observed daily for clinical signs. Deer are euthanized and necropsied when neurologic disease is evident. One animal was euthanized 15 months post-inoculation (MPI) due to an injury. At that time, examination of brain and lymphoid tissues by immunohistochemistry (IHC) and western blot (WB) were negative. A second deer developed pneumonia and was necropsied at 28 MPI. Tissues from this deer were positive for scrapie by IHC and WB. Tissues with PrPd immunoreactivity included brainstem and various lymphoid tissues including tonsil, retropharyngeal and mesenteric lymph nodes, hemal node, Peyer’s patches, and spleen. The remaining deer are under observation for clinical signs. This work demonstrates for the first time that white-tailed deer are susceptible to sheep scrapie by potential natural routes of inoculation. In-depth analysis of tissues will be done to determine similarities between scrapie in deer after intracranial and oral/intranasal inoculation and chronic wasting disease resulting from similar routes of inoculation.
Research Project: Elucidating the Pathobiology and Transmission of Transmissible Spongiform Encephalopathies Location: Virus and Prion Research
Project Number: 5030-32000-228-000-D Project Type: In-House Appropriated
Start Date: Oct 1, 2021 End Date: Sep 30, 2026
Objective:
Objective 1: Develop highly sensitive detection tools to determine the distribution of CWD and scrapie prions in natural hosts (sheep, goats, cervids) and their environment. Objective 2: Investigate the pathobiology of CWD, scrapie prion strains, and atypical TSEs in natural hosts including potential cross species transmission events. Objective 3: Investigate the genetics of CWD susceptibility and resistance in white-tailed deer. Objective 4: Evaluate the presence of and determine the appropriate methodology for CWD strain determination.
Approach:
Eradication or control of a family of diseases is unlikely or impossible when an understanding of the basic mechanisms and influences on transmission are unknown and for which methods to evaluate disease status are lacking. Scrapie and BSE represent the most thoroughly studied TSEs; however, significant knowledge gaps persist with regard to the atypical variants of these diseases. Further, much of the research emphasis to date on genetics of prion disease has focused on the recipient genotype rather than the source. Since both atypical BSE and atypical scrapie have been suggested to occur spontaneously, eradication of these diseases may not be possible unless we expand our understanding of the disease at both the source and recipient level. A better understanding of the tissue distribution and potential transmission of these atypical isolates is critical to understanding what risk these disease variants may pose to ongoing control and eradication efforts. The European epizootic of BSE is waning and efforts to eradicate scrapie in the U.S. and abroad have progressed but are not complete. In the U.S., chronic wasting disease (CWD) presents the most serious challenge to regulatory efforts. CWD appears to be spreading unchecked in both free-ranging and farmed cervids. Methods for antemortem detection of TSEs in general and CWD in particular are needed to fulfill the goal of eradicating scrapie and controlling CWD. Performing these studies will allow us to address critical knowledge gaps that are relevant to developing measures to restrict further disease expansion beyond current, affected populations. Understanding prion disease persistence in animal populations is challenging due to lack of tools for study and a less than complete understanding of transmission among animals within a flock or herd or in naturally occurring reservoirs. In addition to transmission between hosts of like species, free-ranging cervids may come in contact with numerous other species including cattle, sheep, and other susceptible hosts. Transmission of CWD to other species has been studied but limited with regard to the source genotype used. The four primary objectives are inherently linked. Our focus is on developing tools needed for control and research, and using those tools to advance our understanding the complex disease process with the overall goal of eradication and control of disease in livestock, wildlife of economic importance, and potential wildlife reservoirs.
Transmission of the atypical/Nor98 scrapie agent to Suffolk sheep with VRQ/ARQ, ARQ/ARQ, and ARQ/ARR genotypes
Eric D. Cassmann,Najiba Mammadova,S. Jo Moore,Sylvie Benestad,Justin J. Greenlee
Published: February 11, 2021https://doi.org/10.1371/journal.pone.0246503
Citation: Cassmann ED, Mammadova N, Moore SJ, Benestad S, Greenlee JJ (2021) Transmission of the atypical/Nor98 scrapie agent to Suffolk sheep with VRQ/ARQ, ARQ/ARQ, and ARQ/ARR genotypes. PLoS ONE 16(2): e0246503. https://doi.org/10.1371/journal.pone.0246503
Editor: Gianluigi Zanusso, University of Verona, ITALY
Received: November 24, 2020; Accepted: January 21, 2021; Published: February 11, 2021
Abstract
Scrapie is a transmissible spongiform encephalopathy that occurs in sheep. Atypical/Nor98 scrapie occurs in sheep that tend to be resistant to classical scrapie and it is thought to occur spontaneously. The purpose of this study was to test the transmission of the Atypical/Nor98 scrapie agent in three genotypes of Suffolk sheep and characterize the distribution of misfolded prion protein (PrPSc). Ten sheep were intracranially inoculated with brain homogenate from a sheep with Atypical/Nor98 scrapie. All sheep with the ARQ/ARQ and ARQ/ARR genotypes developed Atypical/Nor98 scrapie confirmed by immunohistochemistry, and one sheep with the VRQ/ARQ genotype had detectable PrPSc consistent with Atypical/Nor98 scrapie at the experimental endpoint of 8 years. Sheep with mild early accumulations of PrPSc in the cerebellum had concomitant retinal PrPSc. Accordingly, large amounts of retinal PrPSc were identified in clinically affected sheep and sheep with dense accumulations of PrPSc in the cerebellum.
Introduction
Atypical/Nor98 scrapie (AS) is a fatal prion disease of sheep caused by a misfolded form of the prion protein. Unlike classical scrapie (CS), AS is thought to be a spontaneously occurring disease [1–3]. This is supported by the presence of AS in countries that are free of classical scrapie [4, 5]. It typically affects a single older sheep within a flock, and cases of AS are sporadic and isolated suggesting that natural transmission is unlikely.
The susceptibility of sheep to CS is closely related to polymorphisms in the prion protein gene (PRNP) [6, 7]. Polymorphisms associated with susceptibility or resistance to CS occur at codons 136, 154, and 171. Sheep with the V136R154Q171 and A136R154Q171 haplotypes are susceptible to CS; however, the amino acid polymorphisms A136, R154, and R171 are associated with relative resistance [8–10]. Conversely, naturally occurring cases of AS arise in sheep with the AHQ, ARQ, and ARR haplotypes, and a polymorphism substituting phenylalanine (F) at codon 141 in the PRNP gene increases the risk of AS [11–13].
Several experiments have demonstrated the ability of the AS agent to transmit within the natural host after intracranial inoculation [14–16]. One study found that the AS agent could transmit after a high oral dose of AS brain homogenate [17]. Nonetheless, AS is still considered unlikely to transmit under field conditions; therefore, eradication and surveillance programs for CS have allowed exceptions for AS. As research into AS unfolds, the biological relevance of this disease is gaining attention. Two studies have demonstrated phenotype changes in AS that imply a possible origin for classical scrapie [18] and classical BSE [19]. The present study was designed to generate AS brain material for subsequent projects to investigate interspecies transmission events. Herein, we report our findings after the experimental transmission of AS in sheep with the VRQ/ARQ, ARQ/ARQ, and ARQ/ARR genotypes. This study validates previous work on these genotypes and documents the early accumulation of PrPSc in the retina of sheep with AS.
Results and discussion
All three genotypes of sheep, VRQ/ARQ, ARQ/ARQ, and ARQ/ARR, were susceptible to the AS agent after intracranial inoculation of donor brain homogenate. The diagnosis of AS was confirmed by enzyme immunoassay (EIA) and immunohistochemistry (IHC) with the latter being confirmative. Previous studies have demonstrated experimental transmission of AS to AHQ/AHQ [14, 15] and ARQ/ARQ [16] genotype sheep after intracerebral transmission. Another study showed a phenotypic shift from AS to CH1641-like classical scrapie in a sheep with the AHQ/AHQ genotype [18]. In this study, sheep with the ARQ/ARR genotype had the shortest incubation period ranging from 4.9 years to the experimental endpoint of 8 years (Table 1), and the attack rate was 100% (5/5). Clinical signs were observed in all ARQ/ARR sheep except for a single wether that was culled early to help establish experimental endpoints. Three ARQ/ARR genotype sheep were euthanized due to clinical neurologic disease 4.9–6.7 years post-inoculation. Out of the three genotypes examined, only the ARQ/ARR genotype sheep developed clinical neurologic disease within the eight-year incubation period. In clinically neurologic sheep, we observed stiff legged and hypermetric ataxia (dysmetria), abnormal rear stance, generalized tremors, tremors of the lips, weight loss, and generalized malaise. The spectrum of clinical signs was comparable to other reports of experimental AS in sheep [14, 15]. Three ARQ/ARR genotype sheep (804, 927 and 948) with the most severe dysmetria also had the greatest amount of cerebellar PrPSc. Since dysmetria is typical of animals with cerebellar disease [20], the tendency to observe this as the most consistent and severe neurologic sign is likely related to the characteristic cerebellar accumulation of PrPSc in sheep with AS. The ARQ/ARQ genotype had a long incubation period and remained clinically asymptomatic, as also reported by Okada et al. [16].
Table 1. Results of atypical scrapie transmission in Suffolk sheep. https://doi.org/10.1371/journal.pone.0246503.t001
Sheep with the ARQ/ARQ genotype were positive for AS PrPSc by IHC (2/2). One positive wether remained asymptomatic and was necropsied at the experimental endpoint; whereas, the other sheep was culled due to intercurrent disease around four years post-inoculation. Out of the three original VRQ/ARQ genotype sheep, a single presymptomatic wether had PrPSc in the cerebellum and retina at the experimental endpoint of 8.1 years. The other two sheep succumbed to intercurrent disease, and they did not have detectable PrPSc by means of IHC or EIA at 1.2- and 2.9-years post-inoculation. The VRQ allele, that is generally associated with susceptibility to classical scrapie, is usually absent from naturally occurring AS cases [5, 12, 21]. However, in a study of AS cases from Great Britain, a single VRQ/ARQ case was reported [22]. The prolonged incubation period after intracranial inoculation of AS in a VRQ/ARQ genotype sheep is compatible with the low prevalence in field cases of AS. In fact, field cases of AS often have a polymorphism substituting phenylalanine (F) at codon 141 in the PRNP gene, and most cases have either the AF141RQ or AHQ alleles [12]. All of the sheep in this study contained the amino acid leucine (L) at codon 141.
In order to confirm that sheep had AS and rule out concomitant infection with classical scrapie, all tissues were examined by IHC for PrPSc. The distribution of PrPSc in the brains of sheep was consistent with AS. Immunolabeling of PrPSc appeared as granular and punctate deposits and was largely restricted to the molecular layer of the cerebellum (Fig 1A). Small amounts of punctate and granular staining were also seen in the cerebral cortex, basal nuclei, thalamus, and midbrain. In classical scrapie, PrPSc is found in the dorsal motor nucleus of the vagus nerve (DMNV), one of the early sites of central nervous system accumulation, and in the lymphoid tissue [3]. In the present experiment, PrPSc was observed in the spinal trigeminal tract (Fig 1B), and there was a lack of staining for PrPSc in the DMNV (Fig 1C). Additionally, no PrPSc was detectable by IHC in the lymphoid or peripheral tissues of any sheep; it remained confined to the CNS. Other studies have demonstrated infectivity in peripheral and lymphoid tissues that were IHC negative [17, 23]. This distribution of PrPSc in the present study was consistent with AS in sheep [1, 14]. Furthermore, all genotypes of sheep had similar PrPSc distributions; however, the density of staining was less severe in asymptomatic ARQ/ARQ and VRQ/ARQ genotype sheep. Given a longer incubation period culminating in clinical disease, it is expected that these genotypes would develop more severe PrPSc deposition similar to ARQ/ARR genotype sheep. PrPSc was also found in the spinal cords of each genotype of sheep. Staining of PrPSc appeared as small particulate or fine granular deposits in the dorsal horn. In sheep with the ARQ/ARR genotype, there was minimal PrPSc and it was usually observed in the cervical cord alone. Sheep 929 that lived to the experimental endpoint had PrPSc in both the cervical and thoracic cord segments. In sheep 958 (ARQ/ARQ) and 943 (VRQ/ARQ), there was a mild amount of PrPSc in the dorsal horn of the cervical, thoracic, and lumbar spinal cord segments. This differs from classical scrapie that involves the entire grey matter of the spinal cord in late stage disease [24].
Fig 1. Immunoreactivity of PrPSc in sheep with atypical scrapie.
(A) There is a large amount of PrPSc (red color) within the molecular layer of cerebellum in sheep 958 (ARQ/ARQ). (B) PrPSc (red color) is confined to the spinal trigeminal tract in the medulla oblongata in sheep 948 (ARQ/ARR). (C) The dorsal motor nucleus of the vagus nerve (circle) is devoid of PrPSc in sheep 948. (D) There are multifocal patchy aggregates of PrPSc (red color) in the molecular layer of the cerebellum in sheep 943 (VRQ/ARQ). (E) A small amount of PrPSc (red color) is present in the retina of sheep 943. (F) In sheep 958 there are large amounts of PrPSc (red color) in the plexiform layers of the retina.
We performed both IHC and EIA on cerebellum, cerebrum (parietal cortex), and medulla oblongata at the level of the obex. For the ARQ/ARR and ARQ/ARQ genotype sheep, there was 100% (7/7) agreement between IHC and EIA at detecting PrPSc in the cerebellum. In contrast, the single positive VRQ/ARQ sheep was IHC positive and EIA negative in the cerebellum. This discrepancy was presumably due to the patchy and sparse distribution of PrPSc in the cerebellum (Fig 1D). PrPSc was rarely observed in other brain regions of this animal; however, PrPSc was detected in the retina with IHC (Fig 1E). Moreover, retinal PrPSc was present in each genotype of sheep with atypical scrapie PrPSc in the cerebellum. In clinical sheep with abundant cerebellar PrPSc, there were large amounts of PrPSc in the retina (Fig 1F). PrPSc occurred mostly in the inner and outer plexiform layers, but some minimal labeling was seen in the ganglion and nuclear cell layers. Other reports that describe atypical scrapie do not report retinal PrPSc [1–5, 14–16, 25, 26]. In this study, sheep intracranially inoculated with the atypical scrapie agent accumulated retinal PrPSc in the early stages of disease concomitant with cerebellar PrPSc. This is significant because, sequentially, retinal PrPSc accumulates early in disease; therefore, IHC of retinal tissue may be more sensitive compared to non-cerebellar brain regions.
This experiment demonstrated the transmission of atypical scrapie to three genotypes of sheep after intracranially inoculation, and it is the first study demonstrating experimental transmission to sheep with a VRQ/ARQ PRNP genotype. Additionally, atypical scrapie is further characterized by demonstrating early accumulation of PrPSc in the retina of experimentally inoculated sheep.
Materials and methods Animals for this experiment were derived from a known scrapie-free flock at the United States Department of Agriculture National Animal Disease Center in Ames, IA. This study used ten Suffolk sheep, nine wethers and one ewe. Nine sheep were 1 year old at the time of inoculation. A single sheep, #958, was 2 years old. Sheep in this study had three distinct PRNP genotypes: ARQ/ARQ, ARQ/ARR, and VRQ/ARQ. The genotypes were determined using polymerase chain reaction and Sanger sequencing as previously described [27]. Sheep were homozygous at other known polymorphic sites M112, G127, M137, S138, L141, R151, M157, N176, H180, Q189, T195, T196, R211, Q220, and R223.
The inoculum for this experiment was cerebral homogenate from an AHQ/ARH genotype sheep with atypical scrapie from Norway (Hedalen). The inoculum was obtained through a collaboration with Sylvie Benestad at the Norwegian Veterinary Institute. The brain homogenate was prepared as a 10% w/v homogenate. Sheep were intracranially inoculated with 1 ml (0.1 grams) of brain homogenate. The procedure has been described previously [28]. Briefly, the sheep were anesthetized with xylazine and a surgical field was prepped over the junction of parietal and frontal bones. A 1-cm skin incision was made, and then a 1-mm hole was drilled along the midline of the calvaria. A 9-cm spinal needle was inserted through the hole, and the inoculum was injected into the cranium. Sheep were kept in a biosecurity level 2 indoor pen for two weeks following inoculation and then moved to an outdoor area. They were fed a daily ration of pelleted and loose alfalfa hay. Sheep were monitored daily for any maladies or other clinical signs consistent with scrapie. The experimental endpoint for this experiment included the earliest of either unequivocal neurologic disease or 8 years post-inoculation. The final 8-year endpoint was established by performing a preliminarily cull of sheep 933 to help determine an appropriate endpoint. Sheep were euthanized at the onset of clinical disease or untreatable intercurrent disease. The method of euthanasia was intravenous administration of sodium pentobarbital as per label directions or as directed by an animal resources attending veterinarian. Clinical signs of disease included abnormalities in gate and/or stance, and ataxia.
A full post-mortem examination was performed on each sheep, and a routine set of tissues were collected consistent with previous experiments [29, 30]. A duplicate set of the following tissues were frozen or saved to 10% buffered neutral formalin: brain, spinal cord, pituitary, trigeminal ganglia, eyes, sciatic nerve, third eyelid, palatine tonsil, pharyngeal tonsil, lymph nodes (mesenteric, retropharyngeal, prescapular, and popliteal), spleen, esophagus, forestomaches, intestines, rectal mucosa, thymus, liver, kidney, urinary bladder, pancreas, salivary gland, thyroid gland, adrenal gland, trachea, lung, turbinate, nasal planum, heart, tongue, masseter, diaphragm, triceps brachii, biceps femoris, and psoas major. Formalin fixed tissues were processed, paraffin embedded, and sectioned at optimal thickness (brain, 4 μm; lymphoid, 3 μm; and other, 5 μm) for hematoxylin and eosin staining and IHC. For IHC, a cocktail of the monoclonal anti-PrPSc antibodies F89/160.1.5 [31] and F99/97.6.1 [32] was applied at a concentration of 5 μg/mL using an automated stainer. Frozen portions of cerebellum, parietal cerebral cortex, and brainstem at the level of the obex were homogenized and tested for the presence of PrPSc using a commercially available EIA (HerdChek; IDEXX Laboratories, Westbrook, ME) according to kit instructions.
Ethics statement
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Published: 31 August 2021
Classical BSE prions emerge from asymptomatic pigs challenged with atypical/Nor98 scrapie
Belén Marín, Alicia Otero, Séverine Lugan, Juan Carlos Espinosa, Alba Marín-Moreno, Enric Vidal, Carlos Hedman, Antonio Romero, Martí Pumarola, Juan J. Badiola, Juan María Torres, Olivier Andréoletti & Rosa Bolea
Scientific Reports volume 11, Article number: 17428 (2021) Cite this article
Abstract
Pigs are susceptible to infection with the classical bovine spongiform encephalopathy (C-BSE) agent following experimental inoculation, and PrPSc accumulation was detected in porcine tissues after the inoculation of certain scrapie and chronic wasting disease isolates. However, a robust transmission barrier has been described in this species and, although they were exposed to C-BSE agent in many European countries, no cases of natural transmissible spongiform encephalopathies (TSE) infections have been reported in pigs. Transmission of atypical scrapie to bovinized mice resulted in the emergence of C-BSE prions. Here, we conducted a study to determine if pigs are susceptible to atypical scrapie. To this end, 12, 8–9-month-old minipigs were intracerebrally inoculated with two atypical scrapie sources. Animals were euthanized between 22- and 72-months post inoculation without clinical signs of TSE. All pigs tested negative for PrPSc accumulation by enzyme immunoassay, immunohistochemistry, western blotting and bioassay in porcine PrP mice. Surprisingly, in vitro protein misfolding cyclic amplification demonstrated the presence of C-BSE prions in different brain areas from seven pigs inoculated with both atypical scrapie isolates. Our results suggest that pigs exposed to atypical scrapie prions could become a reservoir for C-BSE and corroborate that C-BSE prions emerge during interspecies passage of atypical scrapie.
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In conclusion, our findings suggest that, although pigs present a strong transmission barrier against the propagation of atypical scrapie, they can propagate low levels of C-BSE prions. The prevalence of atypical scrapie and the presence of infectivity in tissues from atypical scrapie infected sheep are underestimated24,25. Given that pigs have demonstrated being susceptible to other prion diseases, and to propagate prions without showing signs of disease, the measures implemented to ban the inclusion of ruminant proteins in livestock feed must not be interrupted.
Update on chronic wasting disease (CWD) III
EFSA Panel on Biological Hazards (BIOHAZ),Kostas Koutsoumanis,Ana Allende,Avelino Alvarez-Ordoňez,Declan Bolton,Sara Bover-Cid,Marianne Chemaly,Robert Davies,Alessandra De Cesare,Lieve Herman,Friederike Hilbert,Roland Lindqvist,Maarten Nauta,Luisa Peixe,Giuseppe Ru,Panagiotis Skandamis,Elisabetta Suffredini,Olivier Andreoletti,Sylvie L Benestad,Emmanuel Comoy,Romolo Nonno,Teresa da Silva Felicio,Angel Ortiz-Pelaez,Marion M Simmons, …
First published: 11 November 2019 https://doi.org/10.2903/j.efsa.2019.5863
3.2.1.2 Non‐cervid domestic species
The remarkably high rate of natural CWD transmission in the ongoing NA epidemics raises the question of the risk to livestock grazing on CWD‐contaminated shared rangeland and subsequently developing a novel CWD‐related prion disease. This issue has been investigated by transmitting CWD via experimental challenge to cattle, sheep and pigs and to tg mouse lines expressing the relevant species PrP.
For cattle challenged with CWD, PrPSc was detected in approximately 40% of intracerebrally inoculated animals (Hamir et al., 2005, 2006a, 2007). Tg mice expressing bovine PrP have also been challenged with CWD and while published studies have negative outcomes (Tamguney et al., 2009b), unpublished data provided for the purposes of this Opinion indicate that some transmission of individual isolates to bovinised mice is possible (Table 1).
In small ruminant recipients, a low rate of transmission was reported between 35 and 72 months post‐infection (mpi) in ARQ/ARQ and ARQ/VRQ sheep intracerebrally challenged with mule deer CWD (Hamir et al., 2006b), while two out of two ARQ/ARQ sheep intracerebrally inoculated with elk CWD developed clinical disease after 28 mpi (Madsen‐Bouterse et al., 2016). However, tg mice expressing ARQ sheep PrP were resistant (Tamguney et al., 2006) and tg mice expressing the VRQ PrP allele were poorly susceptible to clinical disease (Beringue et al., 2012; Madsen‐Bouterse et al., 2016). In contrast, tg mice expressing VRQ sheep PrP challenged with CWD have resulted in highly efficient, life‐long asymptomatic replication of these prions in the spleen tissue (Beringue et al., 2012).
A recent study investigated the potential for swine to serve as hosts of the CWD agent(s) by intracerebral or oral challenge of crossbred piglets (Moore et al., 2016b, 2017). Pigs sacrificed at 6 mpi, approximately the age at which pigs reach market weight, were clinically healthy and negative by diagnostic tests, although low‐level CWD agent replication could be detected in the CNS by bioassay in tg cervinised mice. Among pigs that were incubated for up to 73 mpi, some gave diagnostic evidence of CWD replication in the brain between 42 and 72 mpi. Importantly, this was observed also in one orally challenged pig at 64 mpi and the presence of low‐level CWD replication was confirmed by mouse bioassay. The authors of this study argued that pigs can support low‐level amplification of CWD prions, although the species barrier to CWD infection is relatively high and that the detection of infectivity in orally inoculated pigs with a mouse bioassay raises the possibility that naturally exposed pigs could act as a reservoir of CWD infectivity.
Research Project: Pathobiology, Genetics, and Detection of Transmissible Spongiform Encephalopathies Location: Virus and Prion Research
Title: Experimental transmission of the chronic wasting disease agent to swine after oral or intracranial inoculation
Author item MOORE, SARAH - Orise Fellow item WEST GREENLEE, M - Iowa State University item KONDRU, NAVEEN - Iowa State University item MANNE, SIREESHA - Iowa State University item Smith, Jodi item Kunkle, Robert item KANTHASAMY, ANUMANTHA - Iowa State University item Greenlee, Justin Submitted to: Journal of Virology Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/6/2017 Publication Date: 9/12/2017
Citation: Moore, S.J., West Greenlee, M.H., Kondru, N., Manne, S., Smith, J.D., Kunkle, R.A., Kanthasamy, A., Greenlee, J.J. 2017. Experimental transmission of the chronic wasting disease agent to swine after oral or intracranial inoculation. Journal of Virology. 91(19):e00926-17. https://doi.org/10.1128/JVI.00926-17.
Interpretive Summary: Chronic wasting disease (CWD) is a fatal disease of wild and captive deer and elk that causes damaging changes in the brain. The infectious agent is an abnormal protein called a prion that has misfolded from its normal state. Whether CWD can transmit to swine is unknown. This study evaluated the potential of pigs to develop CWD after either intracranial or oral inoculation. Our data indicates that swine do accumulate the abnormal prion protein associated with CWD after intracranial or oral inoculation. Further, there was evidence of abnormal prion protein accumulation in lymph nodes. Currently, swine rations in the U.S. could contain animal derived components including materials from deer or elk. In addition, feral swine could be exposed to infected carcasses in areas where CWD is present in wildlife populations. This information is useful to wildlife managers and individuals in the swine and captive cervid industries. These findings could impact future regulations for the disposal of offal from deer and elk slaughtered in commercial operations. U.S. regulators should carefully consider the new information from this study before relaxing feed ban standards designed to control potentially feed borne prion diseases.
Technical Abstract: Chronic wasting disease (CWD) is a naturally occurring, fatal neurodegenerative disease of cervids. The potential for swine to serve as a host for the agent of chronic wasting disease is unknown. The purpose of this study was to investigate the susceptibility of swine to the CWD agent following oral or intracranial experimental inoculation. Crossbred piglets were assigned to one of three groups: intracranially inoculated (n=20), orally inoculated (n=19), or non-inoculated (n=9). At approximately the age at which commercial pigs reach market weight, half of the pigs in each group were culled ('market weight' groups). The remaining pigs ('aged' groups) were allowed to incubate for up to 73 months post inoculation (MPI). Tissues collected at necropsy were examined for disease-associated prion protein (PrPSc) by western blotting (WB), antigen-capture immunoassay (EIA), immunohistochemistry (IHC) and in vitro real-time quaking induced conversion (RT-QuIC). Brain samples from selected pigs were also bioassayed in mice expressing porcine prion protein. Four intracranially inoculated aged pigs and one orally inoculated aged pig were positive by EIA, IHC and/or WB. Using RT-QuIC, PrPSc was detected in lymphoid and/or brain tissue from pigs in all inoculated groups. Bioassay was positive in 4 out of 5 pigs assayed. This study demonstrates that pigs can serve as hosts for CWD, though with scant PrPSc accumulation requiring sensitive detection methods. Detection of infectivity in orally inoculated pigs using mouse bioassay raises the possibility that naturally exposed pigs could act as a reservoir of CWD infectivity.
12 September 2017
Experimental Transmission of the Chronic Wasting Disease Agent to Swine after Oral or Intracranial Inoculation
Authors: S. Jo Moore, M. Heather West Greenlee, Naveen Kondru, Sireesha Manne, Jodi D. Smith, Robert A. Kunkle, Anumantha Kanthasamy, and Justin J. Greenlee
AUTHORS INFO & AFFILIATIONS
Volume 91, Number 19
1 October 2017
ABSTRACT
ABSTRACT
Chronic wasting disease (CWD) is a naturally occurring, fatal neurodegenerative disease of cervids. The potential for swine to serve as hosts for the agent of CWD is unknown. The purpose of this study was to investigate the susceptibility of swine to the CWD agent following experimental oral or intracranial inoculation. Crossbred piglets were assigned to three groups, intracranially inoculated (n = 20), orally inoculated (n = 19), and noninoculated (n = 9). At approximately the age at which commercial pigs reach market weight, half of the pigs in each group were culled (“market weight” groups). The remaining pigs (“aged” groups) were allowed to incubate for up to 73 months postinoculation (mpi). Tissues collected at necropsy were examined for disease-associated prion protein (PrPSc) by Western blotting (WB), antigen capture enzyme immunoassay (EIA), immunohistochemistry (IHC), and in vitro real-time quaking-induced conversion (RT-QuIC). Brain samples from selected pigs were also bioassayed in mice expressing porcine prion protein. Four intracranially inoculated aged pigs and one orally inoculated aged pig were positive by EIA, IHC, and/or WB. By RT-QuIC, PrPSc was detected in lymphoid and/or brain tissue from one or more pigs in each inoculated group. The bioassay was positive in four out of five pigs assayed. This study demonstrates that pigs can support low-level amplification of CWD prions, although the species barrier to CWD infection is relatively high. However, detection of infectivity in orally inoculated pigs with a mouse bioassay raises the possibility that naturally exposed pigs could act as a reservoir of CWD infectivity. IMPORTANCE We challenged domestic swine with the chronic wasting disease agent by inoculation directly into the brain (intracranially) or by oral gavage (orally). Disease-associated prion protein (PrPSc) was detected in brain and lymphoid tissues from intracranially and orally inoculated pigs as early as 8 months of age (6 months postinoculation). Only one pig developed clinical neurologic signs suggestive of prion disease. The amount of PrPSc in the brains and lymphoid tissues of positive pigs was small, especially in orally inoculated pigs. Regardless, positive results obtained with orally inoculated pigs suggest that it may be possible for swine to serve as a reservoir for prion disease under natural conditions.
Research Project: TRANSMISSION, DIFFERENTIATION, AND PATHOBIOLOGY OF TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES Location: Virus and Prion Research
Title: Disease-associated prion protein detected in lymphoid tissues from pigs challenged with the agent of chronic wasting disease
Conclusions: This study demonstrates that PrPSc accumulates in lymphoid tissues from pigs challenged intracranially or orally with the CWD agent, and can be detected as early as 4 months after challenge. CWD-infected pigs rarely develop clinical disease and if they do, they do so after a long incubation period. This raises the possibility that CWD-infected pigs could shed prions into their environment long before they develop clinical disease. Furthermore, lymphoid tissues from CWD-infected pigs could present a potential source of CWD infectivity in the animal and human food chains.
COLORADO THE ORIGIN OF CHRONIC WASTING DISEASE CWD TSE PRION?
*** Spraker suggested an interesting explanation for the occurrence of CWD. The deer pens at the Foot Hills Campus were built some 30-40 years ago by a Dr. Bob Davis. At or abut that time, allegedly, some scrapie work was conducted at this site. When deer were introduced to the pens they occupied ground that had previously been occupied by sheep.
IN CONFIDENCE, REPORT OF AN UNCONVENTIONAL SLOW VIRUS DISEASE IN ANIMALS IN THE USA 1989
ALSO, one of the most, if not the most top TSE Prion God in Science today is Professor Adriano Aguzzi, and he recently commented on just this, on a cwd post on my facebook page August 20 at 1:44pm, quote;
''it pains me to no end to even contemplate the possibility, but it seems entirely plausible that CWD originated from scientist-made spread of scrapie from sheep to deer in the Colorado research facility. If true, a terrible burden for those involved.'' August 20 at 1:44pm ...end
***Moreover, sporadic disease has never been observed in breeding colonies or primate research laboratories, most notably among hundreds of animals over several decades of study at the National Institutes of Health25, and in nearly twenty older animals continuously housed in our own facility.***
Even if the prevailing view is that sporadic CJD is due to the spontaneous formation of CJD prions, it remains possible that its apparent sporadic nature may, at least in part, result from our limited capacity to identify an environmental origin.
THURSDAY, JULY 8, 2021
EFSA Scientific report on the analysis of the 2‐year compulsory intensified monitoring of atypical scrapie
***> AS is considered more likely (subjective probability range 50–66%) that AS is a non-contagious, rather than a contagious, disease.
ATYPICAL SCRAPIE ROUGHLY HAS 50 50 CHANCE ATYPICAL SCRAPIE IS CONTAGIOUS, AS NON-CONTAGIOUS, TAKE YOUR PICK, BUT I SAID IT LONG AGO WHEN USDA OIE ET AL MADE ATYPICAL SCRAPIE A LEGAL TRADING COMODITY, I SAID YOUR PUTTING THE CART BEFORE THE HORSE, AND THAT'S EXACTLY WHAT THEY DID, and it's called in Texas, TEXAS TSE PRION HOLDEM POKER, WHO'S ALL IN $$$
THURSDAY, JULY 8, 2021
EFSA Scientific report on the analysis of the 2‐year compulsory intensified monitoring of atypical scrapie
ACCEPTED MANUSCRIPT
North American and Norwegian Chronic Wasting Disease prions exhibit different potential for interspecies transmission and zoonotic risk
Sandra Pritzkow, Damian Gorski, Frank Ramirez, Glenn C Telling, Sylvie L Benestad, Claudio Soto
The Journal of Infectious Diseases, jiab385, https://doi.org/10.1093/infdis/jiab385
Published: 24 July 2021 Article history Abstract
Chronic wasting disease (CWD) is a rapidly spreading prion disorder affecting various species of wild and captive cervids. The risk that CWD poses to co-habiting animals or more importantly to humans is largely unknown.
In this study we investigated differences in the capacity of CWD isolates obtained from six different cervid species to induce prion conversion in vitro by PMCA. We define and quantify spillover and zoonotic potential indices as the efficiency by which CWD prions sustain prion generation in vitro at expenses of normal prion proteins from various mammals and human, respectively.
Our data suggest that reindeer and red deer from Norway could be the most transmissible CWD prions to other mammals, whereas North American CWD prions were more prone to generate human prions in vitro.
Our results suggest that Norway and North American CWD prions correspond to different strains with distinct spillover and zoonotic potentials.
prions, prion disease, chronic wasting disease, CWD, prion strains, PMCA, spillover potential, zoonotic potential, moose, reindeer, red deer, elk, white-tailed deer, mule deer
Topic: prion diseases prions reindeer wasting disease, chronic norwegian peritoneal mucinous carcinomatosis
Issue Section: Major Article
Chronic wasting disease: a cervid prion infection looming to spillover
Alicia Otero 1 2 3, Camilo Duque Velásquez 1 2, Judd Aiken 2 4, Debbie McKenzie 5 6
Affiliations expand
PMID: 34488900 DOI: 10.1186/s13567-021-00986-y
020
Monday, November 30, 2020
Tunisia has become the second country after Algeria to detect a case of CPD Camel Prion Disease within a year
REPORT OF THE MEETING OF THE OIE SCIENTIFIC COMMISSION FOR ANIMAL DISEASES Paris, 9–13 September 2019
Scientific Commission/September 2019
Tunisia has become the second country after Algeria to detect a case of CPD within a year
10.2. Prion disease in dromedary camels
TUESDAY, SEPTEMBER 07, 2021
Atypical Bovine Spongiform Encephalopathy BSE OIE, FDA 589.2001 FEED REGULATIONS, and Ingestion Therefrom
ZOONOSIS OF SCRAPIE TSE PRION
O.05: Transmission of prions to primates after extended silent incubation periods: Implications for BSE and scrapie risk assessment in human populations
Emmanuel Comoy, Jacqueline Mikol, Valerie Durand, Sophie Luccantoni, Evelyne Correia, Nathalie Lescoutra, Capucine Dehen, and Jean-Philippe Deslys Atomic Energy Commission; Fontenay-aux-Roses, France
Prion diseases (PD) are the unique neurodegenerative proteinopathies reputed to be transmissible under field conditions since decades. The transmission of Bovine Spongiform Encephalopathy (BSE) to humans evidenced that an animal PD might be zoonotic under appropriate conditions. Contrarily, in the absence of obvious (epidemiological or experimental) elements supporting a transmission or genetic predispositions, PD, like the other proteinopathies, are reputed to occur spontaneously (atpical animal prion strains, sporadic CJD summing 80% of human prion cases).
Non-human primate models provided the first evidences supporting the transmissibiity of human prion strains and the zoonotic potential of BSE. Among them, cynomolgus macaques brought major information for BSE risk assessment for human health (Chen, 2014), according to their phylogenetic proximity to humans and extended lifetime. We used this model to assess the zoonotic potential of other animal PD from bovine, ovine and cervid origins even after very long silent incubation periods.
*** We recently observed the direct transmission of a natural classical scrapie isolate to macaque after a 10-year silent incubation period,
***with features similar to some reported for human cases of sporadic CJD, albeit requiring fourfold long incubation than BSE. Scrapie, as recently evoked in humanized mice (Cassard, 2014),
***is the third potentially zoonotic PD (with BSE and L-type BSE),
***thus questioning the origin of human sporadic cases.
We will present an updated panorama of our different transmission studies and discuss the implications of such extended incubation periods on risk assessment of animal PD for human health.
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***thus questioning the origin of human sporadic cases***
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***our findings suggest that possible transmission risk of H-type BSE to sheep and human. Bioassay will be required to determine whether the PMCA products are infectious to these animals.
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***Transmission data also revealed that several scrapie prions propagate in HuPrP-Tg mice with efficiency comparable to that of cattle BSE. While the efficiency of transmission at primary passage was low, subsequent passages resulted in a highly virulent prion disease in both Met129 and Val129 mice.
***Transmission of the different scrapie isolates in these mice leads to the emergence of prion strain phenotypes that showed similar characteristics to those displayed by MM1 or VV2 sCJD prion.
***These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.
PRION 2016 TOKYO
Saturday, April 23, 2016
SCRAPIE WS-01: Prion diseases in animals and zoonotic potential 2016
Prion. 10:S15-S21. 2016 ISSN: 1933-6896 printl 1933-690X online
Taylor & Francis
Prion 2016 Animal Prion Disease Workshop Abstracts
WS-01: Prion diseases in animals and zoonotic potential
Juan Maria Torres a, Olivier Andreoletti b, J uan-Carlos Espinosa a. Vincent Beringue c. Patricia Aguilar a,
Natalia Fernandez-Borges a. and Alba Marin-Moreno a
"Centro de Investigacion en Sanidad Animal ( CISA-INIA ). Valdeolmos, Madrid. Spain; b UMR INRA -ENVT 1225 Interactions Holes Agents Pathogenes. ENVT. Toulouse. France: "UR892. Virologie lmmunologie MolécuIaires, Jouy-en-Josas. France
Dietary exposure to bovine spongiform encephalopathy (BSE) contaminated bovine tissues is considered as the origin of variant Creutzfeldt Jakob (vCJD) disease in human. To date, BSE agent is the only recognized zoonotic prion... Despite the variety of Transmissible Spongiform Encephalopathy (TSE) agents that have been circulating for centuries in farmed ruminants there is no apparent epidemiological link between exposure to ruminant products and the occurrence of other form of TSE in human like sporadic Creutzfeldt Jakob Disease (sCJD). However, the zoonotic potential of the diversity of circulating TSE agents has never been systematically assessed. The major issue in experimental assessment of TSEs zoonotic potential lies in the modeling of the ‘species barrier‘, the biological phenomenon that limits TSE agents’ propagation from a species to another. In the last decade, mice genetically engineered to express normal forms of the human prion protein has proved essential in studying human prions pathogenesis and modeling the capacity of TSEs to cross the human species barrier.
To assess the zoonotic potential of prions circulating in farmed ruminants, we study their transmission ability in transgenic mice expressing human PrPC (HuPrP-Tg). Two lines of mice expressing different forms of the human PrPC (129Met or 129Val) are used to determine the role of the Met129Val dimorphism in susceptibility/resistance to the different agents.
These transmission experiments confirm the ability of BSE prions to propagate in 129M- HuPrP-Tg mice and demonstrate that Met129 homozygotes may be susceptible to BSE in sheep or goat to a greater degree than the BSE agent in cattle and that these agents can convey molecular properties and neuropathological indistinguishable from vCJD. However homozygous 129V mice are resistant to all tested BSE derived prions independently of the originating species suggesting a higher transmission barrier for 129V-PrP variant.
Transmission data also revealed that several scrapie prions propagate in HuPrP-Tg mice with efficiency comparable to that of cattle BSE. While the efficiency of transmission at primary passage was low, subsequent passages resulted in a highly virulent prion disease in both Met129 and Val129 mice.
Transmission of the different scrapie isolates in these mice leads to the emergence of prion strain phenotypes that showed similar characteristics to those displayed by MM1 or VV2 sCJD prion.
These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.
***> why do we not want to do TSE transmission studies on chimpanzees $
5. A positive result from a chimpanzee challenged severly would likely create alarm in some circles even if the result could not be interpreted for man.
***> I have a view that all these agents could be transmitted provided a large enough dose by appropriate routes was given and the animals kept long enough.
***> Until the mechanisms of the species barrier are more clearly understood it might be best to retain that hypothesis.
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R. BRADLEY
Title: Transmission of scrapie prions to primate after an extended silent incubation period)
*** In complement to the recent demonstration that humanized mice are susceptible to scrapie, we report here the first observation of direct transmission of a natural classical scrapie isolate to a macaque after a 10-year incubation period. Neuropathologic examination revealed all of the features of a prion disease: spongiform change, neuronal loss, and accumulation of PrPres throughout the CNS.
*** This observation strengthens the questioning of the harmlessness of scrapie to humans, at a time when protective measures for human and animal health are being dismantled and reduced as c-BSE is considered controlled and being eradicated.
*** Our results underscore the importance of precautionary and protective measures and the necessity for long-term experimental transmission studies to assess the zoonotic potential of other animal prion strains.
***> Moreover, sporadic disease has never been observed in breeding colonies or primate research laboratories, most notably among hundreds of animals over several decades of study at the National Institutes of Health25, and in nearly twenty older animals continuously housed in our own facility. <***
Transmission of scrapie prions to primate after an extended silent incubation period
Emmanuel E. Comoy, Jacqueline Mikol, Sophie Luccantoni-Freire, Evelyne Correia, Nathalie Lescoutra-Etchegaray, Valérie Durand, Capucine Dehen, Olivier Andreoletti, Cristina Casalone, Juergen A. Richt, Justin J. Greenlee, Thierry Baron, Sylvie L. Benestad, Paul Brown & Jean-Philippe Deslys Scientific Reports volume 5, Article number: 11573 (2015) | Download Citation
Abstract
Classical bovine spongiform encephalopathy (c-BSE) is the only animal prion disease reputed to be zoonotic, causing variant Creutzfeldt-Jakob disease (vCJD) in humans and having guided protective measures for animal and human health against animal prion diseases. Recently, partial transmissions to humanized mice showed that the zoonotic potential of scrapie might be similar to c-BSE. We here report the direct transmission of a natural classical scrapie isolate to cynomolgus macaque, a highly relevant model for human prion diseases, after a 10-year silent incubation period, with features similar to those reported for human cases of sporadic CJD. Scrapie is thus actually transmissible to primates with incubation periods compatible with their life expectancy, although fourfold longer than BSE. Long-term experimental transmission studies are necessary to better assess the zoonotic potential of other prion diseases with high prevalence, notably Chronic Wasting Disease of deer and elk and atypical/Nor98 scrapie.
SNIP...
Discussion We describe the transmission of spongiform encephalopathy in a non-human primate inoculated 10 years earlier with a strain of sheep c-scrapie. Because of this extended incubation period in a facility in which other prion diseases are under study, we are obliged to consider two alternative possibilities that might explain its occurrence. We first considered the possibility of a sporadic origin (like CJD in humans). Such an event is extremely improbable because the inoculated animal was 14 years old when the clinical signs appeared, i.e. about 40% through the expected natural lifetime of this species, compared to a peak age incidence of 60–65 years in human sporadic CJD, or about 80% through their expected lifetimes. Moreover, sporadic disease has never been observed in breeding colonies or primate research laboratories, most notably among hundreds of animals over several decades of study at the National Institutes of Health25, and in nearly twenty older animals continuously housed in our own facility.
The second possibility is a laboratory cross-contamination. Three facts make this possibility equally unlikely. First, handling of specimens in our laboratory is performed with fastidious attention to the avoidance of any such cross-contamination. Second, no laboratory cross-contamination has ever been documented in other primate laboratories, including the NIH, even between infected and uninfected animals housed in the same or adjacent cages with daily intimate contact (P. Brown, personal communication). Third, the cerebral lesion profile is different from all the other prion diseases we have studied in this model19, with a correlation between cerebellar lesions (massive spongiform change of Purkinje cells, intense PrPres staining and reactive gliosis26) and ataxia. The iron deposits present in the globus pallidus are a non specific finding that have been reported previously in neurodegenerative diseases and aging27. Conversely, the thalamic lesion was reminiscent of a metabolic disease due to thiamine deficiency28 but blood thiamine levels were within normal limits (data not shown). The preferential distribution of spongiform change in cortex associated with a limited distribution in the brainstem is reminiscent of the lesion profile in MM2c and VV1 sCJD patients29, but interspecies comparison of lesion profiles should be interpreted with caution. It is of note that the same classical scrapie isolate induced TSE in C57Bl/6 mice with similar incubation periods and lesional profiles as a sample derived from a MM1 sCJD patient30.
We are therefore confident that the illness in this cynomolgus macaque represents a true transmission of a sheep c-scrapie isolate directly to an old-world monkey, which taxonomically resides in the primate subdivision (parvorder of catarrhini) that includes humans. With an homology of its PrP protein with humans of 96.4%31, cynomolgus macaque constitutes a highly relevant model for assessing zoonotic risk of prion diseases. Since our initial aim was to show the absence of transmission of scrapie to macaques in the worst-case scenario, we obtained materials from a flock of naturally-infected sheep, affecting animals with different genotypes32. This c-scrapie isolate exhibited complete transmission in ARQ/ARQ sheep (332 ± 56 days) and Tg338 transgenic mice expressing ovine VRQ/VRQ prion protein (220 ± 5 days) (O. Andreoletti, personal communication). From the standpoint of zoonotic risk, it is important to note that sheep with c-scrapie (including the isolate used in our study) have demonstrable infectivity throughout their lymphoreticular system early in the incubation period of the disease (3 months-old for all the lymphoid organs, and as early as 2 months-old in gut-associated lymph nodes)33. In addition, scrapie infectivity has been identified in blood34, milk35 and skeletal muscle36 from asymptomatic but scrapie infected small ruminants which implies a potential dietary exposure for consumers.
Two earlier studies have reported the occurrence of clinical TSE in cynomolgus macaques after exposures to scrapie isolates. In the first study, the “Compton” scrapie isolate (derived from an English sheep) and serially propagated for 9 passages in goats did not transmit TSE in cynomolgus macaque, rhesus macaque or chimpanzee within 7 years following intracerebral challenge1; conversely, after 8 supplementary passages in conventional mice, this “Compton” isolate induced TSE in a cynomolgus macaque 5 years after intracerebral challenge, but rhesus macaques and chimpanzee remained asymptomatic 8.5 years post-exposure8. However, multiple successive passages that are classically used to select laboratory-adapted prion strains can significantly modify the initial properties of a scrapie isolate, thus questioning the relevance of zoonotic potential for the initial sheep-derived isolate. The same isolate had also induced disease into squirrel monkeys (new-world monkey)9. A second historical observation reported that a cynomolgus macaque developed TSE 6 years post-inoculation with brain homogenate from a scrapie-infected Suffolk ewe (derived from USA), whereas a rhesus macaque and a chimpanzee exposed to the same inoculum remained healthy 9 years post-exposure1. This inoculum also induced TSE in squirrel monkeys after 4 passages in mice. Other scrapie transmission attempts in macaque failed but had more shorter periods of observation in comparison to the current study. Further, it is possible that there are differences in the zoonotic potential of different scrapie strains.
The most striking observation in our study is the extended incubation period of scrapie in the macaque model, which has several implications. Firstly, our observations constitute experimental evidence in favor of the zoonotic potential of c-scrapie, at least for this isolate that has been extensively studied32,33,34,35,36. The cross-species zoonotic ability of this isolate should be confirmed by performing duplicate intracerebral exposures and assessing the transmissibility by the oral route (a successful transmission of prion strains through the intracerebral route may not necessarily indicate the potential for oral transmission37). However, such confirmatory experiments may require more than one decade, which is hardly compatible with current general management and support of scientific projects; thus this study should be rather considered as a case report.
Secondly, transmission of c-BSE to primates occurred within 8 years post exposure for the lowest doses able to transmit the disease (the survival period after inoculation is inversely proportional to the initial amount of infectious inoculum). The occurrence of scrapie 10 years after exposure to a high dose (25 mg) of scrapie-infected sheep brain suggests that the macaque has a higher species barrier for sheep c-scrapie than c-BSE, although it is notable that previous studies based on in vitro conversion of PrP suggested that BSE and scrapie prions would have a similar conversion potential for human PrP38.
Thirdly, prion diseases typically have longer incubation periods after oral exposure than after intracerebral inoculations: since humans can develop Kuru 47 years after oral exposure39, an incubation time of several decades after oral exposure to scrapie would therefore be expected, leading the disease to occur in older adults, i.e. the peak age for cases considered to be sporadic disease, and making a distinction between scrapie-associated and truly sporadic disease extremely difficult to appreciate.
Fourthly, epidemiologic evidence is necessary to confirm the zoonotic potential of an animal disease suggested by experimental studies. A relatively short incubation period and a peculiar epidemiological situation (e.g., all the first vCJD cases occurring in the country with the most important ongoing c-BSE epizootic) led to a high degree of suspicion that c-BSE was the cause of vCJD. Sporadic CJD are considered spontaneous diseases with an almost stable and constant worldwide prevalence (0.5–2 cases per million inhabitants per year), and previous epidemiological studies were unable to draw a link between sCJD and classical scrapie6,7,40,41, even though external causes were hypothesized to explain the occurrence of some sCJD clusters42,43,44. However, extended incubation periods exceeding several decades would impair the predictive values of epidemiological surveillance for prion diseases, already weakened by a limited prevalence of prion diseases and the multiplicity of isolates gathered under the phenotypes of “scrapie” and “sporadic CJD”.
Fifthly, considering this 10 year-long incubation period, together with both laboratory and epidemiological evidence of decade or longer intervals between infection and clinical onset of disease, no premature conclusions should be drawn from negative transmission studies in cynomolgus macaques with less than a decade of observation, as in the aforementioned historical transmission studies of scrapie to primates1,8,9. Our observations and those of others45,46 to date are unable to provide definitive evidence regarding the zoonotic potential of CWD, atypical/Nor98 scrapie or H-type BSE. The extended incubation period of the scrapie-affected macaque in the current study also underscores the limitations of rodent models expressing human PrP for assessing the zoonotic potential of some prion diseases since their lifespan remains limited to approximately two years21,47,48. This point is illustrated by the fact that the recently reported transmission of scrapie to humanized mice was not associated with clinical signs for up to 750 days and occurred in an extreme minority of mice with only a marginal increase in attack rate upon second passage13. The low attack rate in these studies is certainly linked to the limited lifespan of mice compared to the very long periods of observation necessary to demonstrate the development of scrapie. Alternatively, one could estimate that a successful second passage is the result of strain adaptation to the species barrier, thus poorly relevant of the real zoonotic potential of the original scrapie isolate of sheep origin49. The development of scrapie in this primate after an incubation period compatible with its lifespan complements the study conducted in transgenic (humanized) mice; taken together these studies suggest that some isolates of sheep scrapie can promote misfolding of the human prion protein and that scrapie can develop within the lifespan of some primate species.
In addition to previous studies on scrapie transmission to primate1,8,9 and the recently published study on transgenic humanized mice13, our results constitute new evidence for recommending that the potential risk of scrapie for human health should not be dismissed. Indeed, human PrP transgenic mice and primates are the most relevant models for investigating the human transmission barrier. To what extent such models are informative for measuring the zoonotic potential of an animal TSE under field exposure conditions is unknown. During the past decades, many protective measures have been successfully implemented to protect cattle from the spread of c-BSE, and some of these measures have been extended to sheep and goats to protect from scrapie according to the principle of precaution. Since cases of c-BSE have greatly reduced in number, those protective measures are currently being challenged and relaxed in the absence of other known zoonotic animal prion disease. We recommend that risk managers should be aware of the long term potential risk to human health of at least certain scrapie isolates, notably for lymphotropic strains like the classical scrapie strain used in the current study. Relatively high amounts of infectivity in peripheral lymphoid organs in animals infected with these strains could lead to contamination of food products produced for human consumption. Efforts should also be maintained to further assess the zoonotic potential of other animal prion strains in long-term studies, notably lymphotropic strains with high prevalence like CWD, which is spreading across North America, and atypical/Nor98 scrapie (Nor98)50 that was first detected in the past two decades and now represents approximately half of all reported cases of prion diseases in small ruminants worldwide, including territories previously considered as scrapie free... Even if the prevailing view is that sporadic CJD is due to the spontaneous formation of CJD prions, it remains possible that its apparent sporadic nature may, at least in part, result from our limited capacity to identify an environmental origin.
1: J Infect Dis 1980 Aug;142(2):205-8
Oral transmission of kuru, Creutzfeldt-Jakob disease, and scrapie to nonhuman primates.
Gibbs CJ Jr, Amyx HL, Bacote A, Masters CL, Gajdusek DC.
Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were exposed to the infectious agents only by their nonforced consumption of known infectious tissues. The asymptomatic incubation period in the one monkey exposed to the virus of kuru was 36 months; that in the two monkeys exposed to the virus of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively. Careful physical examination of the buccal cavities of all of the monkeys failed to reveal signs or oral lesions. One additional monkey similarly exposed to kuru has remained asymptomatic during the 39 months that it has been under observation.
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The successful transmission of kuru, Creutzfeldt-Jakob disease, and scrapie by natural feeding to squirrel monkeys that we have reported provides further grounds for concern that scrapie-infected meat may occasionally give rise in humans to Creutzfeldt-Jakob disease.
PMID: 6997404
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6997404&dopt=Abstract
Recently the question has again been brought up as to whether scrapie is transmissible to man. This has followed reports that the disease has been transmitted to primates. One particularly lurid speculation (Gajdusek 1977) conjectures that the agents of scrapie, kuru, Creutzfeldt-Jakob disease and transmissible encephalopathy of mink are varieties of a single "virus". The U.S. Department of Agriculture concluded that it could "no longer justify or permit scrapie-blood line and scrapie-exposed sheep and goats to be processed for human or animal food at slaughter or rendering plants" (ARC 84/77)" The problem is emphasised by the finding that some strains of scrapie produce lesions identical to the once which characterise the human dementias"
Whether true or not. the hypothesis that these agents might be transmissible to man raises two considerations. First, the safety of laboratory personnel requires prompt attention. Second, action such as the "scorched meat" policy of USDA makes the solution of the acrapie problem urgent if the sheep industry is not to suffer grievously.
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76/10.12/4.6
Nature. 1972 Mar 10;236(5341):73-4.
Transmission of scrapie to the cynomolgus monkey (Macaca fascicularis).
Gibbs CJ Jr, Gajdusek DC.
Nature 236, 73 - 74 (10 March 1972); doi:10.1038/236073a0
Transmission of Scrapie to the Cynomolgus Monkey (Macaca fascicularis)
C. J. GIBBS jun. & D. C. GAJDUSEK
National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland
SCRAPIE has been transmitted to the cynomolgus, or crab-eating, monkey (Macaca fascicularis) with an incubation period of more than 5 yr from the time of intracerebral inoculation of scrapie-infected mouse brain. The animal developed a chronic central nervous system degeneration, with ataxia, tremor and myoclonus with associated severe scrapie-like pathology of intensive astroglial hypertrophy and proliferation, neuronal vacuolation and status spongiosus of grey matter. The strain of scrapie virus used was the eighth passage in Swiss mice (NIH) of a Compton strain of scrapie obtained as ninth intracerebral passage of the agent in goat brain, from Dr R. L. Chandler (ARC, Compton, Berkshire).
THE tse prion aka mad cow type disease is not your normal pathogen.
The TSE prion disease survives ashing to 600 degrees celsius, that’s around 1112 degrees farenheit.
you cannot cook the TSE prion disease out of meat.
you can take the ash and mix it with saline and inject that ash into a mouse, and the mouse will go down with TSE.
Prion Infected Meat-and-Bone Meal Is Still Infectious after Biodiesel Production as well.
the TSE prion agent also survives Simulated Wastewater Treatment Processes.
IN fact, you should also know that the TSE Prion agent will survive in the environment for years, if not decades.
you can bury it and it will not go away.
The TSE agent is capable of infected your water table i.e. Detection of protease-resistant cervid prion protein in water from a CWD-endemic area.
it’s not your ordinary pathogen you can just cook it out and be done with.
***> that’s what’s so worrisome about Iatrogenic mode of transmission, a simple autoclave will not kill this TSE prion agent.
1: J Neurol Neurosurg Psychiatry 1994 Jun;57(6):757-8
***> Transmission of Creutzfeldt-Jakob disease to a chimpanzee by electrodes contaminated during neurosurgery.
Gibbs CJ Jr, Asher DM, Kobrine A, Amyx HL, Sulima MP, Gajdusek DC.
Laboratory of Central Nervous System Studies, National Institute of
Neurological Disorders and Stroke, National Institutes of Health,
Bethesda, MD 20892.
Stereotactic multicontact electrodes used to probe the cerebral cortex of a middle aged woman with progressive dementia were previously implicated in the accidental transmission of Creutzfeldt-Jakob disease (CJD) to two younger patients. The diagnoses of CJD have been confirmed for all three cases. More than two years after their last use in humans, after three cleanings and repeated sterilisation in ethanol and formaldehyde vapour, the electrodes were implanted in the cortex of a chimpanzee. Eighteen months later the animal became ill with CJD. This finding serves to re-emphasise the potential danger posed by reuse of instruments contaminated with the agents of spongiform encephalopathies, even after scrupulous attempts to clean them.
PMID: 8006664 [PubMed - indexed for MEDLINE]
New studies on the heat resistance of hamster-adapted scrapie agent: Threshold survival after ashing at 600°C suggests an inorganic template of replication
Prion Infected Meat-and-Bone Meal Is Still Infectious after Biodiesel Production
MONDAY, APRIL 19, 2021
Evaluation of the application for new alternative biodiesel production process for rendered fat including Category 1 animal by-products (BDI-RepCat® process, AT) ???
Detection of protease-resistant cervid prion protein in water from a CWD-endemic area
A Quantitative Assessment of the Amount of Prion Diverted to Category 1 Materials and Wastewater During Processing
Rapid assessment of bovine spongiform encephalopathy prion inactivation by heat treatment in yellow grease produced in the industrial manufacturing process of meat and bone meals
THURSDAY, FEBRUARY 28, 2019
BSE infectivity survives burial for five years with only limited spread
***> Infectious agent of sheep scrapie may persist in the environment for at least 16 years
***> Nine of these recurrences occurred 14–21 years after culling, apparently as the result of environmental contamination, but outside entry could not always be absolutely excluded.
JOURNAL OF GENERAL VIROLOGY Volume 87, Issue 12
Infectious agent of sheep scrapie may persist in the environment for at least 16 years Free
Gudmundur Georgsson1, Sigurdur Sigurdarson2, Paul Brown3
First Published: 01 December 2006 https://doi.org/10.1099/vir.0.82011-0 ABSTRACT In 1978, a rigorous programme was implemented to stop the spread of, and subsequently eradicate, sheep scrapie in Iceland. Affected flocks were culled, premises were disinfected and, after 2–3 years, restocked with lambs from scrapie-free areas. Between 1978 and 2004, scrapie recurred on 33 farms. Nine of these recurrences occurred 14–21 years after culling, apparently as the result of environmental contamination, but outside entry could not always be absolutely excluded. Of special interest was one farm with a small, completely self-contained flock where scrapie recurred 18 years after culling, 2 years after some lambs had been housed in an old sheep-house that had never been disinfected. Epidemiological investigation established with near certitude that the disease had not been introduced from the outside and it is concluded that the agent may have persisted in the old sheep-house for at least 16 years.
Gudmundur Georgsson,1 Sigurdur Sigurdarson2 and Paul Brown3
Correspondence
Gudmundur Georgsson ggeorgs@hi.is
1 Institute for Experimental Pathology, University of Iceland, Keldur v/vesturlandsveg, IS-112 Reykjavı´k, Iceland
2 Laboratory of the Chief Veterinary Officer, Keldur, Iceland
3 Bethesda, Maryland, USA
Received 7 March 2006 Accepted 6 August 2006
In 1978, a rigorous programme was implemented to stop the spread of, and subsequently eradicate, sheep scrapie in Iceland. Affected flocks were culled, premises were disinfected and, after 2–3 years, restocked with lambs from scrapie-free areas. Between 1978 and 2004, scrapie recurred on 33 farms. Nine of these recurrences occurred 14–21 years after culling, apparently as the result of environmental contamination, but outside entry could not always be absolutely excluded. Of special interest was one farm with a small, completely self-contained flock where scrapie recurred 18 years after culling, 2 years after some lambs had been housed in an old sheephouse that had never been disinfected. Epidemiological investigation established with near certitude that the disease had not been introduced from the outside and it is concluded that the agent may have persisted in the old sheep-house for at least 16 years.
TITLE: PATHOLOGICAL FEATURES OF CHRONIC WASTING DISEASE IN REINDEER AND DEMONSTRATION OF HORIZONTAL TRANSMISSION
*** DECEMBER 2016 CDC EMERGING INFECTIOUS DISEASE JOURNAL CWD HORIZONTAL TRANSMISSION
SEE;
Back around 2000, 2001, or so, I was corresponding with officials abroad during the bse inquiry, passing info back and forth, and some officials from here inside USDA aphis FSIS et al. In fact helped me get into the USA 50 state emergency BSE conference call way back. That one was a doozy. But I always remember what “deep throat” I never knew who they were, but I never forgot;
Some unofficial information from a source on the inside looking out -
Confidential!!!!
As early as 1992-3 there had been long studies conducted on small pastures containing scrapie infected sheep at the sheep research station associated with the Neuropathogenesis Unit in Edinburgh, Scotland. Whether these are documented...I don't know. But personal recounts both heard and recorded in a daily journal indicate that leaving the pastures free and replacing the topsoil completely at least 2 feet of thickness each year for SEVEN years....and then when very clean (proven scrapie free) sheep were placed on these small pastures.... the new sheep also broke out with scrapie and passed it to offspring. I am not sure that TSE contaminated ground could ever be free of the agent!! A very frightening revelation!!!
---end personal email---end...tss
Infectivity surviving ashing to 600*C is (in my opinion) degradable but infective. based on Bown & Gajdusek, (1991), landfill and burial may be assumed to have a reduction factor of 98% (i.e. a factor of 50) over 3 years. CJD-infected brain-tissue remained infectious after storing at room-temperature for 22 months (Tateishi et al, 1988). Scrapie agent is known to remain viable after at least 30 months of desiccation (Wilson et al, 1950). and pastures that had been grazed by scrapie-infected sheep still appeared to be contaminated with scrapie agent three years after they were last occupied by sheep (Palsson, 1979).
Dr. Paul Brown Scrapie Soil Test BSE Inquiry Document
Using in vitro Prion replication for high sensitive detection of prions and prionlike proteins and for understanding mechanisms of transmission.
Claudio Soto Mitchell Center for Alzheimer's diseases and related Brain disorders, Department of Neurology, University of Texas Medical School at Houston.
Prion and prion-like proteins are misfolded protein aggregates with the ability to selfpropagate to spread disease between cells, organs and in some cases across individuals. I n T r a n s m i s s i b l e s p o n g i f o r m encephalopathies (TSEs), prions are mostly composed by a misfolded form of the prion protein (PrPSc), which propagates by transmitting its misfolding to the normal prion protein (PrPC). The availability of a procedure to replicate prions in the laboratory may be important to study the mechanism of prion and prion-like spreading and to develop high sensitive detection of small quantities of misfolded proteins in biological fluids, tissues and environmental samples. Protein Misfolding Cyclic Amplification (PMCA) is a simple, fast and efficient methodology to mimic prion replication in the test tube. PMCA is a platform technology that may enable amplification of any prion-like misfolded protein aggregating through a seeding/nucleation process. In TSEs, PMCA is able to detect the equivalent of one single molecule of infectious PrPSc and propagate prions that maintain high infectivity, strain properties and species specificity. Using PMCA we have been able to detect PrPSc in blood and urine of experimentally infected animals and humans affected by vCJD with high sensitivity and specificity. Recently, we have expanded the principles of PMCA to amplify amyloid-beta (Aβ) and alphasynuclein (α-syn) aggregates implicated in Alzheimer's and Parkinson's diseases, respectively. Experiments are ongoing to study the utility of this technology to detect Aβ and α-syn aggregates in samples of CSF and blood from patients affected by these diseases.
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***>>> Recently, we have been using PMCA to study the role of environmental prion contamination on the horizontal spreading of TSEs. These experiments have focused on the study of the interaction of prions with plants and environmentally relevant surfaces. Our results show that plants (both leaves and roots) bind tightly to prions present in brain extracts and excreta (urine and feces) and retain even small quantities of PrPSc for long periods of time. Strikingly, ingestion of prioncontaminated leaves and roots produced disease with a 100% attack rate and an incubation period not substantially longer than feeding animals directly with scrapie brain homogenate. Furthermore, plants can uptake prions from contaminated soil and transport them to different parts of the plant tissue (stem and leaves). Similarly, prions bind tightly to a variety of environmentally relevant surfaces, including stones, wood, metals, plastic, glass, cement, etc. Prion contaminated surfaces efficiently transmit prion disease when these materials were directly injected into the brain of animals and strikingly when the contaminated surfaces were just placed in the animal cage. These findings demonstrate that environmental materials can efficiently bind infectious prions and act as carriers of infectivity, suggesting that they may play an important role in the horizontal transmission of the disease.
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Since its invention 13 years ago, PMCA has helped to answer fundamental questions of prion propagation and has broad applications in research areas including the food industry, blood bank safety and human and veterinary disease diagnosis.
source reference Prion Conference 2015 abstract book
Grass Plants Bind, Retain, Uptake, and Transport Infectious Prions
Sandra Pritzkow,1 Rodrigo Morales,1 Fabio Moda,1,3 Uffaf Khan,1 Glenn C. Telling,2 Edward Hoover,2 and Claudio Soto1, * 1Mitchell Center for Alzheimer’s Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX 77030, USA
2Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
3Present address: IRCCS Foundation Carlo Besta Neurological Institute, 20133 Milan, Italy *Correspondence: claudio.soto@uth.tmc.edu http://dx.doi.org/10.1016/j.celrep.2015.04.036
SUMMARY
Prions are the protein-based infectious agents responsible for prion diseases. Environmental prion contamination has been implicated in disease transmission. Here, we analyzed the binding and retention of infectious prion protein (PrPSc) to plants. Small quantities of PrPSc contained in diluted brain homogenate or in excretory materials (urine and feces) can bind to wheat grass roots and leaves. Wild-type hamsters were efficiently infected by ingestion of prion-contaminated plants. The prion-plant interaction occurs with prions from diverse origins, including chronic wasting disease. Furthermore, leaves contaminated by spraying with a prion-containing preparation retained PrPSc for several weeks in the living plant. Finally, plants can uptake prions from contaminated soil and transport them to aerial parts of the plant (stem and leaves). These findings demonstrate that plants can efficiently bind infectious prions and act as carriers of infectivity, suggesting a possible role of environmental prion contamination in the horizontal transmission of the disease.
INTRODUCTION
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DISCUSSION
This study shows that plants can efficiently bind prions contained in brain extracts from diverse prion infected animals, including CWD-affected cervids. PrPSc attached to leaves and roots from wheat grass plants remains capable of seeding prion replication in vitro. Surprisingly, the small quantity of PrPSc naturally excreted in urine and feces from sick hamster or cervids was enough to efficiently contaminate plant tissue. Indeed, our results suggest that the majority of excreted PrPSc is efficiently captured by plants’ leaves and roots. Moreover, leaves can be contaminated by spraying them with a prion-containing extract, and PrPSc remains detectable in living plants for as long as the study was performed (several weeks). Remarkably, prion contaminated plants transmit prion disease to animals upon ingestion, producing a 100% attack rate and incubation periods not substantially longer than direct oral administration of sick brain homogenates.
Finally, an unexpected but exciting result was that plants were able to uptake prions from contaminated soil and transport them to aerial parts of the plant tissue. Although it may seem farfetched that plants can uptake proteins from the soil and transport it to the parts above the ground, there are already published reports of this phenomenon (McLaren et al., 1960; Jensen and McLaren, 1960;Paungfoo-Lonhienne et al., 2008). The high resistance of prions to degradation and their ability to efficiently cross biological barriers may play a role in this process. The mechanism by which plants bind, retain, uptake, and transport prions is unknown. We are currently studying the way in which prions interact with plants using purified, radioactively labeled PrPSc to determine specificity of the interaction, association constant, reversibility, saturation, movement, etc.
Epidemiological studies have shown numerous instances of scrapie or CWD recurrence upon reintroduction of animals on pastures previously exposed to prion-infected animals. Indeed, reappearance of scrapie has been documented following fallow periods of up to 16 years (Georgsson et al., 2006), and pastures were shown to retain infectious CWD prions for at least 2 years after exposure (Miller et al., 2004). It is likely that the environmentally mediated transmission of prion diseases depends upon the interaction of prions with diverse elements, including soil, water, environmental surfaces, various invertebrate animals, and plants.
However, since plants are such an important component of the environment and also a major source of food for many animal species, including humans, our results may have far-reaching implications for animal and human health. Currently, the perception of the riskfor animal-to-human prion transmission has beenmostly limited to consumption or exposure to contaminated meat; our results indicate that plants might also be an important vector of transmission that needs to be considered in risk assessment.
RIGINAL RESEARCH ARTICLE
Front. Vet. Sci., 14 September 2015 | https://doi.org/10.3389/fvets.2015.00032
Objects in contact with classical scrapie sheep act as a reservoir for scrapie transmission
imageTimm Konold1*, imageStephen A. C. Hawkins2, imageLisa C. Thurston3, imageBen C. Maddison4, imageKevin C. Gough5, imageAnthony Duarte1 and imageHugh A. Simmons1
1Animal Sciences Unit, Animal and Plant Health Agency Weybridge, Addlestone, UK
2Pathology Department, Animal and Plant Health Agency Weybridge, Addlestone, UK
3Surveillance and Laboratory Services, Animal and Plant Health Agency Penrith, Penrith, UK
4ADAS UK, School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, UK
5School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, UK
Classical scrapie is an environmentally transmissible prion disease of sheep and goats. Prions can persist and remain potentially infectious in the environment for many years and thus pose a risk of infecting animals after re-stocking. In vitro studies using serial protein misfolding cyclic amplification (sPMCA) have suggested that objects on a scrapie-affected sheep farm could contribute to disease transmission. This in vivo study aimed to determine the role of field furniture (water troughs, feeding troughs, fencing, and other objects that sheep may rub against) used by a scrapie-infected sheep flock as a vector for disease transmission to scrapie-free lambs with the prion protein genotype VRQ/VRQ, which is associated with high susceptibility to classical scrapie. When the field furniture was placed in clean accommodation, sheep became infected when exposed to either a water trough (four out of five) or to objects used for rubbing (four out of seven). This field furniture had been used by the scrapie-infected flock 8 weeks earlier and had previously been shown to harbor scrapie prions by sPMCA. Sheep also became infected (20 out of 23) through exposure to contaminated field furniture placed within pasture not used by scrapie-infected sheep for 40 months, even though swabs from this furniture tested negative by PMCA. This infection rate decreased (1 out of 12) on the same paddock after replacement with clean field furniture. Twelve grazing sheep exposed to field furniture not in contact with scrapie-infected sheep for 18 months remained scrapie free. The findings of this study highlight the role of field furniture used by scrapie-infected sheep to act as a reservoir for disease re-introduction although infectivity declines considerably if the field furniture has not been in contact with scrapie-infected sheep for several months. PMCA may not be as sensitive as VRQ/VRQ sheep to test for environmental contamination.
snip...
Discussion
Classical scrapie is an environmentally transmissible disease because it has been reported in naïve, supposedly previously unexposed sheep placed in pastures formerly occupied by scrapie-infected sheep (4, 19, 20).
Although the vector for disease transmission is not known, soil is likely to be an important reservoir for prions (2) where – based on studies in rodents – prions can adhere to minerals as a biologically active form (21) and remain infectious for more than 2 years (22).
Similarly, chronic wasting disease (CWD) has re-occurred in mule deer housed in paddocks used by infected deer 2 years earlier, which was assumed to be through foraging and soil consumption (23).
Our study suggested that the risk of acquiring scrapie infection was greater through exposure to contaminated wooden, plastic, and metal surfaces via water or food troughs, fencing, and hurdles than through grazing.
Drinking from a water trough used by the scrapie flock was sufficient to cause infection in sheep in a clean building.
Exposure to fences and other objects used for rubbing also led to infection, which supported the hypothesis that skin may be a vector for disease transmission (9).
The risk of these objects to cause infection was further demonstrated when 87% of 23 sheep presented with PrPSc in lymphoid tissue after grazing on one of the paddocks, which contained metal hurdles, a metal lamb creep and a water trough in contact with the scrapie flock up to 8 weeks earlier, whereas no infection had been demonstrated previously in sheep grazing on this paddock, when equipped with new fencing and field furniture.
When the contaminated furniture and fencing were removed, the infection rate dropped significantly to 8% of 12 sheep, with soil of the paddock as the most likely source of infection caused by shedding of prions from the scrapie-infected sheep in this paddock up to a week earlier.
This study also indicated that the level of contamination of field furniture sufficient to cause infection was dependent on two factors: stage of incubation period and time of last use by scrapie-infected sheep.
Drinking from a water trough that had been used by scrapie sheep in the predominantly pre-clinical phase did not appear to cause infection, whereas infection was shown in sheep drinking from the water trough used by scrapie sheep in the later stage of the disease.
It is possible that contamination occurred through shedding of prions in saliva, which may have contaminated the surface of the water trough and subsequently the water when it was refilled.
Contamination appeared to be sufficient to cause infection only if the trough was in contact with sheep that included clinical cases.
Indeed, there is an increased risk of bodily fluid infectivity with disease progression in scrapie (24) and CWD (25) based on PrPSc detection by sPMCA.
Although ultraviolet light and heat under natural conditions do not inactivate prions (26), furniture in contact with the scrapie flock, which was assumed to be sufficiently contaminated to cause infection, did not act as vector for disease if not used for 18 months, which suggest that the weathering process alone was sufficient to inactivate prions.
PrPSc detection by sPMCA is increasingly used as a surrogate for infectivity measurements by bioassay in sheep or mice.
In this reported study, however, the levels of PrPSc present in the environment were below the limit of detection of the sPMCA method, yet were still sufficient to cause infection of in-contact animals.
In the present study, the outdoor objects were removed from the infected flock 8 weeks prior to sampling and were positive by sPMCA at very low levels (2 out of 37 reactions).
As this sPMCA assay also yielded 2 positive reactions out of 139 in samples from the scrapie-free farm, the sPMCA assay could not detect PrPSc on any of the objects above the background of the assay.
False positive reactions with sPMCA at a low frequency associated with de novo formation of infectious prions have been reported (27, 28).
This is in contrast to our previous study where we demonstrated that outdoor objects that had been in contact with the scrapie-infected flock up to 20 days prior to sampling harbored PrPSc that was detectable by sPMCA analysis [4 out of 15 reactions (12)] and was significantly more positive by the assay compared to analogous samples from the scrapie-free farm.
This discrepancy could be due to the use of a different sPMCA substrate between the studies that may alter the efficiency of amplification of the environmental PrPSc.
In addition, the present study had a longer timeframe between the objects being in contact with the infected flock and sampling, which may affect the levels of extractable PrPSc.
Alternatively, there may be potentially patchy contamination of this furniture with PrPSc, which may have been missed by swabbing.
The failure of sPMCA to detect CWD-associated PrP in saliva from clinically affected deer despite confirmation of infectivity in saliva-inoculated transgenic mice was associated with as yet unidentified inhibitors in saliva (29), and it is possible that the sensitivity of sPMCA is affected by other substances in the tested material.
In addition, sampling of amplifiable PrPSc and subsequent detection by sPMCA may be more difficult from furniture exposed to weather, which is supported by the observation that PrPSc was detected by sPMCA more frequently in indoor than outdoor furniture (12).
A recent experimental study has demonstrated that repeated cycles of drying and wetting of prion-contaminated soil, equivalent to what is expected under natural weathering conditions, could reduce PMCA amplification efficiency and extend the incubation period in hamsters inoculated with soil samples (30).
This seems to apply also to this study even though the reduction in infectivity was more dramatic in the sPMCA assays than in the sheep model.
Sheep were not kept until clinical end-point, which would have enabled us to compare incubation periods, but the lack of infection in sheep exposed to furniture that had not been in contact with scrapie sheep for a longer time period supports the hypothesis that prion degradation and subsequent loss of infectivity occurs even under natural conditions.
In conclusion, the results in the current study indicate that removal of furniture that had been in contact with scrapie-infected animals should be recommended, particularly since cleaning and decontamination may not effectively remove scrapie infectivity (31), even though infectivity declines considerably if the pasture and the field furniture have not been in contact with scrapie-infected sheep for several months. As sPMCA failed to detect PrPSc in furniture that was subjected to weathering, even though exposure led to infection in sheep, this method may not always be reliable in predicting the risk of scrapie infection through environmental contamination.
These results suggest that the VRQ/VRQ sheep model may be more sensitive than sPMCA for the detection of environmentally associated scrapie, and suggest that extremely low levels of scrapie contamination are able to cause infection in susceptible sheep genotypes.
Keywords: classical scrapie, prion, transmissible spongiform encephalopathy, sheep, field furniture, reservoir, serial protein misfolding cyclic amplification
Chemical Inactivation of Prions Is Altered by Binding to the Soil Mineral Montmorillonite
Clarissa J. Booth, Stuart Siegfried Lichtenberg, Richard J. Chappell, and Joel A. Pedersen* Cite this: ACS Infect. Dis. 2021, XXXX, XXX, XXX-XXX Publication Date:March 31, 2021 https://doi.org/10.1021/acsinfecdis.0c00860 © 2021 American Chemical Society
Abstract
Environmental routes of transmission contribute to the spread of the prion diseases chronic wasting disease of deer and elk and scrapie of sheep and goats. Prions can persist in soils and other environmental matrices and remain infectious for years. Prions bind avidly to the common soil mineral montmorillonite, and such binding can dramatically increase oral disease transmission. Decontamination of soil in captive facilities and natural habitats requires inactivation agents that are effective when prions are bound to soil microparticles. Here, we investigate the inactivation of free and montmorillonite-bound prions with sodium hydroxide, acidic pH, Environ LpH, and sodium hypochlorite. Immunoblotting and bioassays confirm that sodium hydroxide and sodium hypochlorite are effective for prion deactivation, although montmorillonite appears to reduce the efficacy of hypochlorite. Acidic conditions slightly reduce prion infectivity, and the acidic phenolic disinfectant Environ LpH produces slight reductions in infectivity and immunoreactivity. The extent to which the association with montmorillonite protects prions from chemical inactivation appears influenced by the effect of chemical agents on the clay structure and surface pH. When clay morphology remains relatively unaltered, as when exposed to hypochlorite, montmorillonite-bound prions appear to be protected from inactivation. In contrast, when the clay structure is substantially transformed, as when exposed to high concentrations of sodium hydroxide, the attachment to montmorillonite does not slow degradation. A reduction in surface pH appears to cause slight disruptions in clay structure, which enhances degradation under these conditions. We expect our findings will aid the development of remediation approaches for successful decontamination of prion-contaminated sites.
Front. Vet. Sci., 04 March 2021 | https://doi.org/10.3389/fvets.2021.643754
Real-Time Quaking-Induced Conversion Detection of PrPSc in Fecal Samples From Chronic Wasting Disease Infected White-Tailed Deer Using Bank Vole Substrate
Soyoun Hwang, Justin J. Greenlee and Eric M. Nicholson*
Virus and Prion Research Unit, National Animal Disease Center, United States Department of Agriculture, Agricultural Research Service, Ames, IA, United States
Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy (TSE) that is fatal to free-range and captive cervids. CWD has been reported in the United States, Canada, South Korea, Norway, Finland, and Sweden, and the case numbers in both wild and farmed cervids are increasing rapidly. Studies indicate that lateral transmission of cervids likely occurs through the shedding of infectious prions in saliva, feces, urine, and blood into the environment. Therefore, the detection of CWD early in the incubation time is advantageous for disease management. In this study, we adapt real-time quacking-induced conversion (RT-QuIC) assays to detect the seeding activity of CWD prions in feces samples from clinical and preclinical white-tailed deer. By optimizing reaction conditions for temperature as well as the salt and salt concentration, prion seeding activity from both clinical and preclinical animals were detected by RT-QuIC. More specifically, all fecal samples collected from 6 to 30 months post inoculation showed seeding activity under the conditions of study. The combination of a highly sensitive detection tool paired with a sample type that may be collected non-invasively allows a useful tool to support CWD surveillance in wild and captive cervids.
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Altogether, we confirm again that RT-QuIC is a powerful tool to detect infectious fecal prions from CWD infected white-tailed deer. Use of feces is a non-invasive and non-stressing approach to sampling of animals, of particular importance for non-domesticated animals that may be less tolerant to the handling required for sampling by other means. This is of importance to the management of both wild and farmed cervids and is also of use in experimental settings where repeated sampling of an individual animal would be otherwise difficult. Ultimately, fecal sampling may prove useful in the determination of disease prevalence in a geographic region or within a herd.
WEDNESDAY, MAY 29, 2019
***> Incomplete inactivation of atypical scrapie following recommended autoclave decontamination procedures <***
THURSDAY, DECEMBER 31, 2020
Autoclave treatment of the classical scrapie agent US No. 13-7 and experimental inoculation to susceptible VRQ/ARQ sheep via the oral route results in decreased transmission efficiency
TEXAS CWD STRAIN
77. Assessing chronic wasting disease strain differences in free-ranging cervids across the United States
Kaitlyn M. Wagnera, Caitlin Ott-Connb, Kelly Strakab, Bob Dittmarc, Jasmine Battend, Robyn Piercea, Mercedes Hennessya, Elizabeth Gordona, Brett Israela, Jenn Ballarde and Mark D Zabela
aPrion Research Center at Colorado State University; bMichigan Department of Natural Resources; cTexas Parks and Wildlife Department; dMissouri Department of Conservation, 5. Arkansas Game and Fish Commission CONTACT Kaitlyn M. Wagner miedkait@rams.colostate.edu
ABSTRACT
Background/Introduction: Chronic wasting disease (CWD) is an invariably fatal prion disease affecting captive and free-ranging cervids, including white-tailed deer, mule deer, moose, elk, and reindeer. Since the initial description of the disease in the 1960’s, CWD has spread to 23 states, 3 Canadian Provinces, South Korea, Norway and, most recently, Finland. While some outbreaks of CWD were caused by transport of infected animals from endemic regions, the origin of CWD in other epizootics is unclear and has not been characterized. Previous studies have shown that there are two distinct strains of CWD. However, the continuous spread and the unclear origin of several outbreaks warrant continued surveillance and further characterization of strain diversity.
Materials and Methods: To address these knowledge gaps, we used biochemical tests to assess strain differences between CWD outbreaks in Michigan, Texas, Missouri, and Colorado, USA. Brain or lymph node samples were homogenized and digested in 50 µg/mL proteinase K (PK). These samples were then run on a Western blot to assess glycoform ratio and electrophoretic mobility. Texas samples were digested in 100 µg/mL PK. To assess conformational stability, brain or lymph node homogenates were incubated in increasing concentrations of guanidine hydrochloride from 0 M to 4 M in 0.5 M increments. Samples were then precipitated in methanol overnight, washed and PK digested in 50 µg/mL PK before slot blotting.
Results: Our results have found significant differences in glycoform ratio between CWD from Michigan and Colorado, but no differences were observed in conformational stability assays. Interestingly, when testing our CWD isolates from Texas to analyse electrophoretic mobility and glycoform ratio, we found that these samples did not exhibit the characteristic band shift when treated with PK, but PK resistant material remained. Additionally, results from our conformational stability assay demonstrate a unique profile of these Texas isolates. Testing of samples from Missouri is currently underway.
Conclusions: Thus far, our data indicate that there are strain differences between CWD circulating in Michigan and CWD in Colorado and provide important insight into CWD strain differences between two non-contiguous outbreaks. We have also identified a unique strain of CWD in Texas with biochemical strain properties not seen in any of our other CWD isolates. These results highlight the importance of continued surveillance to better understand this devastating disease. These results have important implications for CWD emergence, evolution and our understanding of prion strain heterogeneity on the landscape.
SUNDAY, APRIL 14, 2019
Chronic Wasting Disease TSE Prion Strains everything in Texas is bigger, better, and badder The disease devastating deer herds may also threaten human health
Scientists are exploring the origins of chronic wasting disease before it becomes truly catastrophic. Rae Ellen Bichell
Image credit: David Parsons/Istock
April 8, 2019
Wagner and Zabel have suggested a possible answer: Perhaps, they say, there is not just one chronic wasting disease, but rather a bunch of different strains of it. And those different strains could be emerging at different times across the globe.
One day in late February, in their laboratory in Fort Collins, Colorado, Wagner and Zabel compared the prions from the brains of CWD-infected deer in Texas with those of elk in Colorado. They want to know if the proteins were all mangled in the same way, or not. “If they are different, this would suggest that we have different strain properties, which is evidence as we're building our case that we might have multiple strains of CWD circulating in the U.S.,” says Wagner.
Step one is to see if they’re equally easy to destroy using a chemical called guanidine. The shape of a prion dictates everything, including the way it interacts with an animal’s cells and the ease with which chemicals can unfold it.
“Moment of truth,” said Wagner, as she and Zabel huddled around a computer, waiting for results to come through. When they did, Zabel was surprised.
“Wow,” he said. “Unlike anything we've seen before.”
The prions from the Texas deer were a lot harder to destroy than the ones from the Colorado elk. In fact, the guanidine barely damaged them at all. “We’ve never seen that before in any prion strain, which means that it has a completely different structure than we've ever seen before,” says Zabel. And that suggests that it might be a very different kind of chronic wasting disease. The researchers ran the same test on another Texas deer, with the same results.
Now, these are only the preliminary results from a few animals. Wagner and Zabel have a lot more experiments to do. But if future tests come to the same conclusion, it would support their hypothesis that there are multiple strains of chronic wasting disease out there, all with different origins. That, in turn, could mean that this disease will become even trickier to manage than it already is.
And, Zabel adds, there’s something else. “If it's still evolving, it may still evolve into a form that could potentially, eventually affect humans,” he says.
Zabel is not the only one worried about that possibility.
OSTERHOLM, THE EPIDEMIOLOGIST from Minnesota, is also concerned. He directs the Center for Infectious Disease Research and Policy at the University of Minnesota, and is serving a one-year stint as a “Science Envoy for Health Security” with the U.S. State Department. In February, he told Minnesota lawmakers that when it comes to chronic wasting disease, we are playing with fire. “You are going to hear from people that this is not going to be a problem other than a game farm issue. You're going to hear from people that it's not going to transmit to people, and I hope they're right, but I wouldn't bet on it,” he said. “And if we lose this one and haven’t done all we can do, we will pay a price.”
If that wasn’t warning enough, he added: “Just remember what happened in England.”
TUESDAY, APRIL 20, 2021
Friday, December 14, 2012
DEFRA U.K. What is the risk of Chronic Wasting Disease CWD being introduced into Great Britain? A Qualitative Risk Assessment October 2012
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In the USA, under the Food and Drug Administration's BSE Feed Regulation (21 CFR 589.2000) most material (exceptions include milk, tallow, and gelatin) from deer and elk is prohibited for use in feed for ruminant animals. With regards to feed for non-ruminant animals, under FDA law, CWD positive deer may not be used for any animal feed or feed ingredients. For elk and deer considered at high risk for CWD, the FDA recommends that these animals do not enter the animal feed system. However, this recommendation is guidance and not a requirement by law. Animals considered at high risk for CWD include:
1) animals from areas declared to be endemic for CWD and/or to be CWD eradication zones and
2) deer and elk that at some time during the 60-month period prior to slaughter were in a captive herd that contained a CWD-positive animal.
Therefore, in the USA, materials from cervids other than CWD positive animals may be used in animal feed and feed ingredients for non-ruminants.
The amount of animal PAP that is of deer and/or elk origin imported from the USA to GB can not be determined, however, as it is not specified in TRACES.
It may constitute a small percentage of the 8412 kilos of non-fish origin processed animal proteins that were imported from US into GB in 2011.
Overall, therefore, it is considered there is a __greater than negligible risk___ that (nonruminant) animal feed and pet food containing deer and/or elk protein is imported into GB.
There is uncertainty associated with this estimate given the lack of data on the amount of deer and/or elk protein possibly being imported in these products.
snip.....
36% in 2007 (Almberg et al., 2011). In such areas, population declines of deer of up to 30 to 50% have been observed (Almberg et al., 2011). In areas of Colorado, the prevalence can be as high as 30% (EFSA, 2011). The clinical signs of CWD in affected adults are weight loss and behavioural changes that can span weeks or months (Williams, 2005). In addition, signs might include excessive salivation, behavioural alterations including a fixed stare and changes in interaction with other animals in the herd, and an altered stance (Williams, 2005). These signs are indistinguishable from cervids experimentally infected with bovine spongiform encephalopathy (BSE). Given this, if CWD was to be introduced into countries with BSE such as GB, for example, infected deer populations would need to be tested to differentiate if they were infected with CWD or BSE to minimise the risk of BSE entering the human food-chain via affected venison. snip..... The rate of transmission of CWD has been reported to be as high as 30% and can approach 100% among captive animals in endemic areas (Safar et al., 2008).
snip.....
In summary, in endemic areas, there is a medium probability that the soil and surrounding environment is contaminated with CWD prions and in a bioavailable form. In rural areas where CWD has not been reported and deer are present, there is a greater than negligible risk the soil is contaminated with CWD prion. snip..... In summary, given the volume of tourists, hunters and servicemen moving between GB and North America, the probability of at least one person travelling to/from a CWD affected area and, in doing so, contaminating their clothing, footwear and/or equipment prior to arriving in GB is greater than negligible... For deer hunters, specifically, the risk is likely to be greater given the increased contact with deer and their environment. However, there is significant uncertainty associated with these estimates.
snip.....
Therefore, it is considered that farmed and park deer may have a higher probability of exposure to CWD transferred to the environment than wild deer given the restricted habitat range and higher frequency of contact with tourists and returning GB residents.
snip.....
***> READ THIS VERY, VERY, CAREFULLY, AUGUST 1997 MAD COW FEED BAN WAS A SHAM, AS I HAVE STATED SINCE 1997! 3 FAILSAFES THE FDA ET AL PREACHED AS IF IT WERE THE GOSPEL, IN TERMS OF MAD COW BSE DISEASE IN USA, AND WHY IT IS/WAS/NOT A PROBLEM FOR THE USA, and those are;
BSE TESTING (failed terribly and proven to be a sham)
BSE SURVEILLANCE (failed terribly and proven to be a sham)
BSE 589.2001 FEED REGULATIONS (another colossal failure, and proven to be a sham)
these are facts folks. trump et al just admitted it with the feed ban.
see;
FDA Reports on VFD Compliance
John Maday
August 30, 2019 09:46 AM VFD-Form 007 (640x427)
Before and after the current Veterinary Feed Directive rules took full effect in January, 2017, the FDA focused primarily on education and outreach. ( John Maday ) Before and after the current Veterinary Feed Directive (VFD) rules took full effect in January, 2017, the FDA focused primarily on education and outreach to help feed mills, veterinarians and producers understand and comply with the requirements. Since then, FDA has gradually increased the number of VFD inspections and initiated enforcement actions when necessary. On August 29, FDA released its first report on inspection and compliance activities. The report, titled “Summary Assessment of Veterinary Feed Directive Compliance Activities Conducted in Fiscal Years 2016 – 2018,” is available online.
SUNDAY, SEPTEMBER 1, 2019
***> FDA Reports on VFD Compliance
Published: 26 September 2021
Generation of human chronic wasting disease in transgenic mice
Zerui Wang, Kefeng Qin, Manuel V. Camacho, Ignazio Cali, Jue Yuan, Pingping Shen, Justin Greenlee, Qingzhong Kong, James A. Mastrianni & Wen-Quan Zou
Acta Neuropathologica Communications volume 9, Article number: 158 (2021)
Abstract
Chronic wasting disease (CWD) is a cervid prion disease caused by the accumulation of an infectious misfolded conformer (PrPSc) of cellular prion protein (PrPC). It has been spreading rapidly in North America and also found in Asia and Europe. Although bovine spongiform encephalopathy (i.e. mad cow disease) is the only animal prion disease known to be zoonotic, the transmissibility of CWD to humans remains uncertain. Here we report the generation of the first CWD-derived infectious human PrPSc by elk CWD PrPSc-seeded conversion of PrPC in normal human brain homogenates using in vitro protein misfolding cyclic amplification (PMCA). Western blotting with human PrP selective antibody confirmed that the PMCA-generated protease-resistant PrPSc was derived from the human PrPC substrate. Two lines of humanized transgenic mice expressing human PrP with either Val or Met at the polymorphic codon 129 developed clinical prion disease following intracerebral inoculation with the PMCA-generated CWD-derived human PrPSc. Diseased mice exhibited distinct PrPSc patterns and neuropathological changes in the brain. Our study, using PMCA and animal bioassays, provides the first evidence that CWD PrPSc can cross the species barrier to convert human PrPC into infectious PrPSc that can produce bona fide prion disease when inoculated into humanized transgenic mice.
Snip...
It is worth noting that the annual number of sporadic CJD (sCJD) cases in the USA has increased, with the total number of suspected and confirmed sCJD cases rising from 284 in 2003 to 511 in 2017 (https://www.cdc.gov/prions/cjd/occurrence-transmission.html). The greatly enhanced CJD surveillance and an aging population in the USA certainly contributed to the observed increase in annual sCJD case numbers in recent years, but the possibility cannot be excluded that some of the increased sCJD prevalence is linked to CWD exposure.
In the present study, using serial protein misfolding cyclic amplification (sPMCA) assay we generate PrPSc by seeding CWD prions in normal human brain homogenates. Importantly, we reveal that two lines of humanized Tg mice expressing human PrP-129VV and 129MM develop prion diseases upon intracerebral inoculation of the abnormal PrP generated by sPMCA. We believe that our study provides the first opportunity to dissect the clinical, pathological and biochemical features of the CWD-derived human prion disease in two lines of humanized Tg mice expressing two major human PrP genotypes, respectively.
In conclusion, our findings suggest that, although pigs present a strong transmission barrier against the propagation of atypical scrapie, they can propagate low levels of C-BSE prions. The prevalence of atypical scrapie and the presence of infectivity in tissues from atypical scrapie infected sheep are underestimated24,25. Given that pigs have demonstrated being susceptible to other prion diseases, and to propagate prions without showing signs of disease, the measures implemented to ban the inclusion of ruminant proteins in livestock feed must not be interrupted.
>>> The prevalence of atypical scrapie and the presence of infectivity in tissues from atypical scrapie infected sheep are underestimated24,25.
>>> Given that pigs have demonstrated being susceptible to other prion diseases, and to propagate prions without showing signs of disease, the measures implemented to ban the inclusion of ruminant proteins in livestock feed must not be interrupted.
***> This is a variant of scrapie that we consider non-contagious.
***> Atypical/Nor98 scrapie occurs in sheep that tend to be resistant to classical scrapie and it is thought to occur spontaneously.
***> Unlike classical scrapie (CS), AS is thought to be a spontaneously occurring disease [1–3].
***> It typically affects a single older sheep within a flock, and cases of AS are sporadic and isolated suggesting that natural transmission is unlikely.
***> Several experiments have demonstrated the ability of the AS agent to transmit within the natural host after intracranial inoculation [14–16].
***> One study found that the AS agent could transmit after a high oral dose of AS brain homogenate [17].
***> Nonetheless, AS is still considered unlikely to transmit under field conditions; therefore, eradication and surveillance programs for CS have allowed exceptions for AS.
I disagree, and this is a foolish move taking this stance, because Science has shown us that the atypical scrapie IS TRANSMISSIBLE!
EFSA SAYS ATYPICAL SCRAPIE ROUGHLY HAS 50 50 CHANCE ATYPICAL SCRAPIE IS CONTAGIOUS, AS NON-CONTAGIOUS!
TO CONTINUE THIS CHARADE, THAT ''variant of scrapie that we consider non-contagious'' and ''AS is thought to be a spontaneously occurring disease'', OR THAT ATYPICAL CWD IS NOT CONTATIOUS, WILL ONLY CONTINUE TO SPREAD CWD TSE PRION, INCLUDING ATYPICAL SCRAPIE AND ATYPICAL CWD, IMO, FROM EXISTING SCIENCE TO DATE, IT'S A RISK NO ONE SHOULD TAKE. ATYPICAL SCRAPIE ROUGHLY HAS 50 50 CHANCE ATYPICAL SCRAPIE IS CONTAGIOUS, AS NON-CONTAGIOUS, TAKE YOUR PICK, BUT I SAID IT LONG AGO WHEN USDA OIE ET AL MADE ATYPICAL SCRAPIE A LEGAL TRADING COMODITY, I SAID YOUR PUTTING THE CART BEFORE THE HORSE, AND THAT'S EXACTLY WHAT THEY DID, and it's called in Texas, TEXAS TSE PRION HOLDEM POKER, WHO'S ALL IN $$$ it's a lose, lose, game they play, because once a tse prion strain jumps species, all bets are off, anything goes...terry
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