CHRONIC WASTING DISEASE CWD PRION2012 Aerosol, Inhalation transmission, Scrapie, cats, species barrier, burial, and more
CHRONIC WASTING DISEASE CWD PRION2012 Aerosol, Inhalation transmission, Scrapie, cats, species barrier, burial, and more
PO-031: Aerosol transmission of chronic wasting disease to white-tailed
deer
Nathaniel Denkers,1 Jeanette Hayes-Klug,1 Kelly Anderson,1 Sally Dahmes,2
David Osborn,3 Karl Miller,3 Robert Warren,3 Candace Mathiason,1 Edward Hoover1
1Colorado State University; Fort Collins, CO USA; 2WASCO Inc.; Monroe, GA
USA; 3Warnell School of Forestry and Natural Resources, University of Georgia;
Athens, GA USA
Purpose. A signature feature of chronic wasting disease (CWD) is its
efficient lateral transmission in nature, almost surely by mucosal exposure. Our
previous studies employing Tg(cerPrP) mice determined that CWD can be
transmitted to a susceptible host by aerosol exposure, a route with relatively
little investigation. The present study was designed to determine whether CWD is
transmissible by aerosol to a native cervid host, white-tailed deer.
Materials and Methods. Nine white-tailed deer were exposed to two (2)
aerosol doses of a 5% w/v CWD+ (n = 6) or CWD- (n = 3) brain homogenate,
delivered via the nasal passages using a customized aerosol apparatus. At
3-month intervals post inoculation (mpi), tonsil and recto-anal
mucosa-associated lymphoid tissue (RAMALT) biopsies were collected and assayed
for CWD infection by protein misfolding cyclic amplification (PMCA), western
blotting (WB), and immunohistochemistry (IHC).
Results. At 3 mpi and 6 mpi, tonsil and RAMALT biopsies were collected
from 5 of the 6 CWD + aerosol-exposed deer. Three of the 5 (60%) tested positive
for CWD by PMCA but not IHC or western blot analysis at 3 mpi. By 6 mpi, 5 of 5
(100%) were tonsil and/or RAMALT biopsy positive by at least two of the three
assays. Biopsies were collected from all CWD+ aerosol-exposed deer at 9 mpi,
with 6 of 6 (100%) tonsil and/ or RAMALT positive by western blot or IHC. At 10
mpi 3 of the 6 prion-exposed deer have developed early clinical signs of CWD
infection (hyperphagia, polydypsia, wide leg stance and head/neck
dorsi-flexion). All sham-inoculated deer are showing no clinical signs and have
remained CWD negative as assessed by all three assays. Interestingly, the prion
dose delivered to the deer by aerosol-exposure is estimated to be 20-fold lower
than the historical oral dose that has resulted in detectable CWD infection at 6
or 12 mpi.
Conclusions. This study documents the first aerosol transmission of CWD in
deer. These results further infer that aerosolized prions facilitate CWD
transmission with greater efficiency than does oral exposure to a larger prion
dose. Thus exposure via the respiratory mucosa may be significant in the facile
spread of CWD in deer and perhaps in prion transmission overall.
PO-073: Multiple routes of prion transepithelial transport in the nasal
cavity following inhalation
Anthony Kincaid, Shawn Feilmann, Melissa Clouse, Albert Lorenzo, Jason
Bartz Creighton University; Omaha, NE USA
Introduction. Inhalation of either prion-infected brain homogenate or
aerosolized prions has been shown to cause disease, and in the case of
inhalation of infected brain homogenate, the nasal route of infection has been
shown to be 10–100 times more efficient than the oral route. The cell types
involved in the in vivo transport of prions across the nasal cavity epithelium
have not been determined. M cells in the follicular associated epithelium have
been shown to mediate transcellular transport of prions in vitro and in the gut
of experimentally infected mice. We tested the hypothesis that M-cell mediated
transport was responsible for prion entry across nasal cavity epithelium
following inhalation.
Materials and Methods. Hamsters were inoculated extranasally with 50 or
100ul of infected (n = 31) or mock-infected (n = 13) brain homogenate. Control
animals were inoculated with buffer (n = 4) or were untreated (n = 5). Following
survival periods ranging from 15 to 180 min, animals were perfused, skulls were
decalcified and nasal cavities were embedded in paraffin. Tissue sections were
cut and processed immunohistochemically for glial fibrillary acidic protein to
identify brain homogenate, or for the disease-associated form of the prion
protein. Tissue sections not further than 112 um apart through the entire extent
of the nasal cavity were analyzed using light microscopy; photomicrographs were
obtained wherever inoculum was observed on the surface of, within, or deep to
the nasal mucosa for each animal.
Results. Infected or uninfected brain homogenate was identified within the
nasal cavities of animals at all time points and was seen crossing the nasal
cavity epithelium within minutes of inoculation; the transepithelial transport
of brain homogenate continued for up to 3 h after inoculation. Infected or
uninfected brain homogenate was seen adhering to, or located within, M cells at
all time points. However, larger volumes of infected or uninfected brain
homogenate were identified crossing between cells of the olfactory and
respiratory epithelia in multiple locations. In addition, infected or uninfected
brain homogenate was identified within the lumen of lymphatic vessels in the
lamina propria beneath the nasal mucosa at all time points.
Conclusion. Transepithelial transport of prions across nasal cavity mucosa
begins within minutes of inhalation and can continue for up to 3 h. While M
cells appear to transport prions across the follicular associated epithelium,
larger amounts of prions are transported between the cells of the respiratory
and olfactory epithelia, where they immediately enter the lymphatic vessels in
the lamina propria. Thus, inhaled prions can be spread via lymph draining the
nasal cavity and have access to somatic and autonomic nerves in the lamina
propria of the nasal cavity. The increased efficiency of the nasal cavity route
of infection compared with the oral route may be due to the rapid and prolonged
transport of prions between cells of the respiratory and olfactory
epithelia.
PO-033: Replication efficiency of soil-bound prions varies with soil type
Shannon Bartelt-Hunt,1 Samuel Saunders,1 Ronald Shikiya,2 Katie
Langenfeld,2 Jason Bartz2 1University of Nebraska-Lincoln; Omaha, NE USA;
2Creighton University; Omaha, NE USA
Prion sorption to soil is thought to play an important role in the
transmission of scrapie and chronic wasting disease (CWD) via the environment.
Sorption of PrP to soil and soil minerals is influenced by the strain and
species of PrPSc and by soil characteristics. However, the ability of soil-bound
prions to convert PrPc to PrPSc under these wide-ranging conditions remains
poorly understood. We developed a semiquantitative protein misfolding cyclic
amplification (PMCA) protocol to evaluate replication efficiency of soil-bound
prions. Binding of the hyper (HY) strain of transmissible mink encephalopathy
(TME) (hamster) prions to a silty clay loam soil yielded a greater-than-1-log
decrease in PMCA replication efficiency with a corresponding 1.3-log reduction
in titer. The increased binding of PrPSc to soil over time corresponded with a
decrease in PMCA replication efficiency. The PMCA efficiency of bound prions
varied with soil type, where prions bound to clay and organic surfaces exhibited
significantly lower replication efficiencies while prions bound to sand
exhibited no apparent difference in replication efficiency compared to unbound
controls. PMCA results from hamster and CWD agent-infected elk prions yielded
similar findings. Given that PrPSc adsorption affinity varies with soil type,
the overall balance between prion adsorption affinity and replication efficiency
for the dominant soil types of an area may be a significant determinant in the
environmental transmission of prion diseases.
PO-039: A comparison of scrapie and chronic wasting disease in white-tailed
deer
Justin Greenlee, Jodi Smith, Eric Nicholson US Dept. Agriculture;
Agricultural Research Service, National Animal Disease Center; Ames, IA USA
Interspecies transmission studies afford the opportunity to better
understand the potential host range and origins of prion diseases. The purpose
of these experiments was to determine susceptibility of white-tailed deer (WTD)
to scrapie and to compare the resultant clinical signs, lesions, and molecular
profiles of PrPSc to those of chronic wasting disease (CWD). We inoculated WTD
intracranially (IC; n = 5) and by a natural route of exposure (concurrent oral
and intranasal (IN); n = 5) with a US scrapie isolate.
All deer were inoculated with a 10% (wt/vol) brain homogenate from sheep
with scrapie (1ml IC, 1 ml IN, 30 ml oral). All deer inoculated by the
intracranial route had evidence of PrPSc accumulation. PrPSc was detected in
lymphoid tissues as early as 7 months-post-inoculation (PI) and a single deer
that was necropsied at 15.6 months had widespread distribution of PrPSc
highlighting that PrPSc is widely distributed in the CNS and lymphoid tissues
prior to the onset of clinical signs. IC inoculated deer necropsied after 20
months PI (3/5) had clinical signs, spongiform encephalopathy, and widespread
distribution of PrPSc in neural and lymphoid tissues.
The results of this study suggest that there are many similarities in the
manifestation of CWD and scrapie in WTD after IC inoculation including early and
widespread presence of PrPSc in lymphoid tissues, clinical signs of depression
and weight loss progressing to wasting, and an incubation time of 21-23 months.
Moreover, western blots (WB) done on brain material from the obex region have a
molecular profile similar to CWD and distinct from tissues of the cerebrum or
the scrapie inoculum. However, results of microscopic and IHC examination
indicate that there are differences between the lesions expected in CWD and
those that occur in deer with scrapie: amyloid plaques were not noted in any
sections of brain examined from these deer and the pattern of immunoreactivity
by IHC was diffuse rather than plaque-like.
After a natural route of exposure, 100% of WTD were susceptible to
scrapie. Deer developed clinical signs of wasting and mental depression and were
necropsied from 28 to 33 months PI. Tissues from these deer were positive for
PrPSc by IHC and WB. Similar to IC inoculated deer, samples from these deer
exhibited two different molecular profiles: samples from obex resembled CWD
whereas those from cerebrum were similar to the original scrapie inoculum. On
further examination by WB using a panel of antibodies, the tissues from deer
with scrapie exhibit properties differing from tissues either from sheep with
scrapie or WTD with CWD. Samples from WTD with CWD or sheep with scrapie are
strongly immunoreactive when probed with mAb P4, however, samples from WTD with
scrapie are only weakly immunoreactive. In contrast, when probed with mAb’s 6H4
or SAF 84, samples from sheep with scrapie and WTD with CWD are weakly
immunoreactive and samples from WTD with scrapie are strongly positive. This
work demonstrates that WTD are highly susceptible to sheep scrapie, but on first
passage, scrapie in WTD is differentiable from CWD.
PO-041: Susceptibility of domestic cats to CWD infection
Amy Nalls, Jeanette Hayes-Klug, Kelly Anderson, Davis Seelig, Kevin
Carnes, Susan Kraft, Edward Hoover, Candace Mathiason
Colorado State University; Fort Collins, CO USA
Domestic and non-domestic cats have been shown to be susceptible to feline
spongiform encephalopathy (FSE); very likely due to consumption of bovine
spongiform encephalopathy (BSE) contaminated meat. Because domestic and
free-ranging nondomestic felids scavenge cervid carcasses, including those in
areas affected by chronic wasting disease (CWD), we evaluated the susceptibility
of domestic cats to CWD infection experimentally. Groups of n = 5 cats each were
inoculated either intracerebrally (IC) or orally (PO) with CWD-infected deer
brain homogenate.
Between 40 and 43 months two IC-inoculated cats developed slowly
progressive symptoms including weight loss, anorexia, polydipsia, patterned
motor behaviors, and ataxia”’ultimately mandating euthanasia. PrPCWD was
detected in the brains of these animals by western blot, immunohistochemistry
(IHC), and quaking-induced conversion (RT-QuIC) assays. No clinical signs of TSE
were detected in the remaining primary passage cats at 86 months pi.
Feline-adapted CWD (FelCWD) was sub-passaged into groups (n = 4 or 5) of cats by
IC, PO, and IP/SQ routes.
All 5 IC inoculated cats developed symptoms of disease 20–24 months pi
(approximately half the incubation period of primary passage). Additional
symptoms in these animals included increasing aggressiveness and hyper
responsiveness. FelCWD was demonstrated in the brains of all the affected cats
by western blot and IHC. Currently, 3 of 4 IP/SQ, and 1 of 4 PO inoculated cats
have developed abnormal behavior patterns consistent with the early stage of
feline CWD. Magnetic resonance imaging (MRI) has been performed on 11 cats (6
clinically ill, 2 asymptomatic, and 3 age-matched negative controls).
Abnormalities were detected in 4 of 6 clinically ill cats and included
multifocal signal changes consistent with inflammation, ventricular size
increases, more prominent sulci, and white matter tract cavitation.
These results demonstrate that CWD can be transmitted and adapted to the
domestic cat, and raise the potential for cervid-to-feline transmission in
nature.
PO-055: Transgenetic modeling of the CWD species barrier to humans
Eri Saijo,1 Sehun Kim,2 Claudio Soto,3 Glenn Telling2 1University of
Kentucky College of Medicine; Fort Collins, CO USA; 2Department of Microbiology,
Immunology and Pathology; Colorado State University; Fort Collins, CO USA ;
3Department of Neurology; University of Texas Houston Medical School; Houston,
TX USA
Our recent studies raise significant concerns about the zoonotic potential
of CWD. First, we showed that tissues consumed by humans derived from deer or
elk with CWD, including skeletal muscle and antler velvet, harbor infectious
prions. In other studies, cervid PrPSc converted human PrPC after CWD prions
were stabilized by successive passages in vitro or in vivo.
We also identified at least two distinct strains of CWD, referred to as
CWD1 and CWD2, the host-range properties of which are currently undefined. Other
studies showed that codon 129, and the corresponding 132 residue in elk,
significantly influenced the transmission of BSE and CWD prions respectively in
transgenic (Tg) mouse models.
We inoculated Tg mice expressing human PrP encoding either methionine (M)
or valine (V) at codon 129 with deer or elk CWD prions that previously produced
disease in Tg mice expressing deer PrP with characteristics typical of CWD1 and
CWD2 strains, as well as CWD prions that had been passaged multiple times in Tg
mice expressing deer PrP.
While most Tg mice remained free of signs of prion disease for >260
days, small numbers of inoculated mice developed multiple, progressive
neurological signs, that were consistent with prion disease. However,
examination of brain materials from diseased mice failed to confirm the presence
of protease-resistant human PrP. These preliminary results are consistent with a
significant species barrier in humans to these CWD strains, and indicate that
the 129 polymorphism does not modulate susceptibility.
PO-056: PrPCWD profiling of white-tailed deer (Odocoileus virginianus)
with different Prnp genotypes following experimental oral infection
Camilo Duque Velasquez,1 Allen Herbst,1 Chad Johnson,2 Judd Aiken,1 Debbie
McKenzie1 1Centre for Prions and Protein Folding Diseases; University of
Alberta; Edmonton, AB Canada; 2Department of Soil Science; University of
Wisconsin; Madison, WI USA
Chronic wasting disease (CWD) affects captive and free-ranging cervid
populations in North America and farmed cervids of South Korea. CWD and scrapie
are the only prion diseases in which the transmission occurs horizontally. The
cervid Prnp gene is polymorphic at various positions. The effect of these
changes on infection is influenced by the sequence and structure compatibility
between the host and the infectious source. Prion strains have been described
virtually in every prion disease and strongly impact disease characteristics
(clinical symptoms, neuropathological profiles, incubation periods, species
tropism as well as biochemical and biophysical properties of the abnormally
folded prion protein). Prion protein sequence differences can result, upon
subsequent infection, in the generation of novel strains as documented in sheep
scrapie. We have previously shown that Prnp polymorphisms influence
susceptibility to CWD in free-ranging white-tailed deer. In CWD-positive deer
populations, alleles Q95G96 (wt) were over-represented compared to the H95G96
and Q95S96 alleles. Experimental oral infection of white-tailed deer with known
Prnp genotypes (with inoculum from CWDpositive wt/wt deer) confirmed the link
between prion protein primary sequence and the progression of disease.
Heterozygous interference occurred in varying degrees as evidenced by the
difference in the extension of the incubation period as an effect of alleles
Q95S96 and H95G96. Interestingly, the biochemical profiles of the wt/Q95S96 and
wt/H95G96 isolates resemble the wt/wt, differing only in the amount of protease
resistant PrPCWD present suggesting that the wt allele is preferentially
converted. PrPCWD profiling revealed differences between deer with at least one
wt allele and the H95G96/Q95S96 deer suggesting that this PrPCWD is unique
compared to the PrPCWD from wt/wt animals.
PO-057: Host factors influence prion strain adaptation
Crystal Meyerett Reid, Mark Zabel Colorado State University; Fort Collins,
CO USA
Background. Chronic Wasting disease (CWD) is one of many prion-mediated
diseases known as transmissible spongiform encephalopathies (TSEs). There is
ever-increasing biological and biochemical evidence that prion pathogenesis is
caused by the conversion of the normal host protein (PrPC) into an abnormal
disease causing conformation (PrPRES). How prions encipher heritable strain
properties without nucleic acid remains unclear. Previously we have shown that
host factors have contributed to the adaptation of an original deer CWD prion
strain to transgenic mice.
Materials and Methods. We assessed strain differences using biological and
biochemical assays and found that amplified cervid prions and serial-passaged
cervid prions were significantly different than that of the original cervid
strain. It is possible that prion mutation and adaptation can broaden the host
range. Previous reports, however, indicate that there is a strict species
barrier preventing CWD infection in wildtype mice.
Results. Here we show the generation of a mouse-adapted strain of CWD upon
serial passage into transgenic cervidized mice and then subsequent passage into
wildtype mice. All wildtype mice remained non-clinical upon first passage but
became completely susceptible after second passage with similar incubation times
to those of mice terminally ill from a mouse adapted scrapie strain. Inoculation
of our mouse adapted CWD strain back into cervidized mice delayed progression to
terminal disease.
Conclusion. We conclude that prion strain adaptation and mutation is
highly dependent upon host factors and host encoded PrPC primary sequence. Upon
serial passage the adapted prion strain shares more characteristics with prion
strains from the new host rather than the original species.
OR-12: Chronic wasting disease transmission and pathogenesis in cervid and
non-cervid Species
Edward A. Hoover, Candace K. Mathiason, Nicholas J. Haley, Timothy D. Kurt,
Davis M. Seelig, Nathaniel D. Denkers, Amy V. Nalls, Mark D. Zabel, and Glenn C.
Telling
Prion Research Program, Department of Microbiology, Immunology, and
Pathology; Colorado State University; Fort Collins, CO USA
Since its recognition as a TSE in the late 1970s, chronic wasting disease
(CWD) of cervids has been distinguished by its facile spread and is now
recognized in 18 states, 2 Canadian provinces, and South Korea. The efficient
horizontal spread of CWD reflects a prion/host relationship that facilitates
efficient mucosal uptake, peripheral lymphoid amplification, and dissemination
by exploiting excretory tissues and their products, helping to establish
indirect/environmental and well as direct (e.g., salivary) transmission. Recent
studies from our group also support the likelihood of early life mother to
offspring and aerosol CWD prion transmission. Studies of cervid CWD exposure by
natural routes indicate that incubation period for detection of overt infection,
while still uncertain, may be much longer than originally thought.
Several non-cervid species can be infected by CWD experimentally (e.g.,
ferrets, voles, cats) with consequent species-specific disease phenotypes. The
species-adapted prions so generated can be transmitted by mucosal, i.e., more
natural, routes. Whether non-cervid species sympatric with deer/elk can be
infected in nature, however, remains unknown. In vitro CWD prion amplification
studies, in particular sPMCA, can foreshadow in vivo susceptibility and suggest
the importance of the PrPC rigid loop region in species barrier permissiveness.
Trans-species CWD amplification appears to broaden the host range/strain
characteristics of the resultant prions. The origins of CWD remain unknown,
however, the existence of multiple CWD prion strains/ quasi-species, the
mechanisms of prion shedding/dissemination, and the relationship between sheep
scrapie and CWD merit further investigation.
PO-060: Transmission of chronic wasting disease from mother to offspring
Candace Mathiason, Amy Nalls, Stephenie Fullaway, Kelly Anderson, Jeanette
Hayes-Klug, Nicholas Haley, Edward Hoover
Colorado State University; Fort Collins, CO USA
To investigate the role mother to offspring transmission plays in chronic
wasting disease (CWD) we have developed a cervid model employing the Reeve’s
muntjac deer (Muntiacus reevesi). Eight muntjac doe were orally inoculated with
CWD and tested PrPCWD lymphoid positive by 4 mo post infection. Twelve fawns
were born to these eight CWD-infected doe, 3 were born viable, 6 were born
non-viable, and 3 were harvested as fetuses (1 each from first, second or third
trimester of pregnancy) from CWDinfected doe euthanized at end-stage disease.
The viable fawns have been monitored for CWD infection by immunohistochemistry
(IHC) performed on serial tonsil and rectal lymphoid tissue biopsies. One fawn
that was IHC PrPCWD positive at 40 d of age is now, at 28 mo of age, showing
early clinical signs associated with CWD infection. Moreover, CWD prions have
been detected by sPMCA in placenta, brain, spleen and mesenteric lymphoid tissue
harvested from 5 full-term non-viable fawns, and in fetal placenta and brain
tissue harvested in utero from the second and third trimester fetuses.
Additional tissues and pregnancy related fluids from doe and offspring are being
analyzed for CWD prions. In summary, using the muntjac deer model we have
demonstrated CWD clinical disease in an offspring born to a CWD-infected doe,
and in utero transmission of CWD from mother to offspring. These studies provide
basis to further investigate the mechanisms of maternal transfer of prions.
PO-081: Chronic wasting disease in the cat— Similarities to feline
spongiform encephalopathy (FSE)
Davis Seelig, Amy Nalls, Maryanne Flasik, Victoria Frank, Candace
Mathiason, Edward Hoover Colorado State University; Fort Collins, CO USA
Background and Introduction. Chronic wasting disease (CWD) is an
efficiently transmitted prion disease of cervids with an as yet to be fully
defined host range. Moreover, the risk that CWD poses to feline predators and
scavangers, through crossspecies consumption and subsequent transmission, is
unknown. Previous and ongoing studies in our laboratory evaluating the
susceptibility of domestic cats (Felis catus) to CWD (Mathiason et. al.,
NeuroPrion 2011, Nalls et. al., NeuroPrion 2012) have documented the
susceptibility of domestic cats to CWD following intracerebral (IC) inoculation.
However, many of the pathologic features of feline-adapted CWD, including the
neural and systemic patterns of PrPCWD accumulation and neuropathology, remain
unknown.
The chief objectives of this work were:
(1) to design a sensitive, enhanced immunohistochemical (E-IHC) protocol
for the detection of CWD prions (PrPCWD) in feline tissues;
(2) to document the systemic distribution of PrPCWD in CWD-infected cats
through E-IHC;
(3) to utilize single and multiple-label immunostaining and laser scanning
confocal microscopy (LSCM) to provide insights into the subcellular patterns of
PrPCWD accumulation and neuropathologic features of CWD-infected cats; and
(4) to compare feline CWD to the other known feline TSE Materials and
Methods. Periodate-lysine-paraformaldehyde (PLP)-fixed, paraffin-embedded
(PLP-PE) from terminal, IC-inoculated (n = 9) and sham-inoculated (n = 2), 1st
and 2nd passage, CWD-infected cats were examined by E-IHC for the presence of
PrPCWD and its association with markers of cell phenotype and organelles.
Results. The most sensitive E-IHC technique for the detection of PrPCWD in
feline tissues incorporated a combination of slide pretreatment with
proteinase-K (PK) in concert with tyramide signal amplification (TSA). With this
protocol, we identified PrPCWD deposits throughout the CNS, which, in the 1st
passage cats was primarily restricted to the obex, but increased in distribution
and severity upon 2nd passage to include a number of midbrain nuclei, cortical
gray matter, the thalamus and hypothalamus, and the hippocampus. Peripheral
PrPCWD deposits were detected only in the 2nd passage cats, and included the
enteric nervous system, the Peyer’s patches, and the retropharyngeal and
mesenteric lymph nodes. PrPCWD was not detected in the sham-inoculated cats.
Moreover, using multi-label analysis, intracellular PrPCWD aggregates were
seen in association with neurofilament heavy chain (NFH)-positive neurons and
GFAP-positive astrocytes. In addition, large aggregates of intracellular PrPCWD
were identified within LAMP1-positive lysosomes.
Conclusions. Feline PrPCWD is present in CNS neurons, astrocytes and
LAMP-1-positive lysosomes. The morphologic overlap between the PrPCWD deposits
in feline CWD and BSE-origin feline spongiform encephalopathy (FSE), implicates
the importance of the host as a key determinant in the development of prion
neuropathology and suggest a signature for detection of potential spontaneous
feline prion disease.
PO-099: Estimating the risk of CWD transmission to humans—An interim report
of a comprehensive study in non-human primates
Ann-Christin Schmaedicke DPZ; Goettingen, Germany
Chronic Wasting Disease (CWD) is a transmissible prion disease that occurs
primarily among North American cervid species. CWD has emerged as a prion
disease in captive as well as freeranging cervids with rising incidence.
Continuous consumption of cervid-derived products in conjunction with increasing
CWD prevalence suggests a risk for human exposure to CWD prions.
Although surveillance data collected in the North American population did
not provide epidemiological evidence for CWD transmissions to humans it remains
unclear whether a biological risk for such transmissions exists or can be
excluded. In order to gauge the potential transmissibility of CWD to humans, a
comprehensive CWD risk assessment in cynomolgus macaques has been initiated. To
test for the CWD interspecies transmission to humans, we used a primate species
previously shown to mimic the BSE susceptibility of humans. In addition, this
species is phylogenetically close to humans with a homologous amino acid
sequence of the prion protein. When we assessed the genotype of macaque PrP, the
homozygosity for methionine at codon 129 was confirmed in all animals.
The zoonotic potential of CWD is evaluated by challenging groups of
animals via different inoculation routes. General transmissibility of CWD to
macaques is tested by intracerebral (i.c.) inoculation of brain homogenate from
CWD-infected white-tailed deer (WTD) and elk. This was either done by direct
injection of 10 mg CWDWTD to two animals (> 880 dpi) or by surgical
implantation of CWD-WTD or CWD-elk contaminated steel wires in two animals (>
750 dpi) or three animals (> 400 dpi), respectively.
To address the risk of hunters while field dressing carcasses, we
inoculated two animals with CWD-WTD by dermal scarification (> 920 dpi). To
simulate human consumption of CWDinfected food products, we orally challenged
three animals with 10 g CWD-WTD brain (> 820 dpi) and three animals with 3 kg
CWD muscle tissue from different cervid species (> 950 dpi) by repeated
feeding. Mock-inoculated macaques are co-housed in the same cage allowing
exposure to saliva and faeces of CWDinoculated macaques.
To date, all inoculated animals remain asymptomatic. Cerebrospinal fluid
and blood from all animals were and are going to be collected bimonthly,
processed and stored in a repository. Analysis of these samples using
ultrasensitive prion detection methods has been initiated. Oral challenge of 50
mg BSE to cynomolgus macaques can lead to fatal disease only after more than 5 y
of incubation time (1952 dpi).
Thus, to estimate whether CWD could be transmitted to macaques or not, we
assume that observation of challenged animals would be necessary for at least
8–10 y.
PO-248: TSE infectivity survives burial for five years with little
reduction in titer
Allister Smith, Robert Somerville, Karen Fernie The Roslin Institute and
R(D)SVS; University of Edinburgh; Edinburgh, UK
BSE infected animals, BSE-contaminated materials and other sources of TSE
(prion) infection, such as carcasses from scrapie infected sheep, CWD infected
deer and cadavers of individuals infected with CJD may all end up in the
environment through burial or other methods of disposal. They may continue to
act as a reservoir of TSE infectivity if cattle or other susceptible animals
were to be exposed to these sources in the future. In order to address these
concerns, we performed two large scale demonstration experiments under field
conditions which were designed to mimic some of the ways by which TSE infected
materials may have been disposed of. The project examined the fate of TSE
infectivity over a period of five years in two scenarios; when the infectivity
was contained within bovine heads and when the infectivity was buried without
any containment. Two soil types were compared: a sandy loam and a clay loam. We
used the 301V TSE strain which was derived by serial passage of BSE in VM
mice.
TSE infectivity was recovered from all the heads exhumed annually for five
years from both types of soil, with little reduction in the amount of
infectivity throughout the period of the experiment. Small amounts of
infectivity were found in the soil immediately surrounding the heads, but not in
samples remote from them. Similarly there was no evidence of significant lateral
movement of infectivity from the buried bolus. However large amounts of TSE
infectivity were recovered at the site of burial of both boluses. There was
limited vertical upward movement of infectivity from the bolus buried in clay
soil and downward movement from the bolus buried in sandy soil.
Now that these experiments are completed we conclude that TSE infectivity
is likely to survive burial for long periods of time with minimal loss of
infectivity and restricted movement from the site of burial. These experiments
emphasize that the environment is a viable reservoir for retaining large
quantities of TSE infectivity, and reinforce the importance of risk assessment
when disposing of this type of infectious material.
see more here ;
Epidemiology Update March 23, 2006
As of today, 13 locations and 32 movements of cattle have been examined
with 27 of those being substantially completed. Additional investigations of
locations and herds will continue. In addition, state and federal officials have
confirmed that a black bull calf was born in 2005 to the index animal (the red
cow). The calf was taken by the owner to a local stockyard in July 2005 where
the calf died. The calf was appropriately disposed of in a local landfill and
did not enter the human or animal food chain. http://www.aphis.usda.gov/newsroom/hot_issues/bse/bse_al_epi-update.shtml
> The calf was appropriately disposed of in a local
> landfill and did not enter the human or animal food chain.
Wednesday, May 30, 2012
PO-248: TSE infectivity survives burial for five years with little
reduction in titer
TSS
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