CWD, FECES, ORAL LESIONS, Aerosol and intranasal transmission

O.11.1

Prions in feces of asymptomatic deer

Gültekin Tamgüney1,2, Michael W. Miller3, Lisa L. Wolfe3, Tracey M. Sirochman3, David V. Glidden4, Christina Palmer 1, Azucena Lemus5, Stephen J. DeArmond5, Stanley B. Prusiner1,2

1Institute for Neurodegenerative Diseases, University of California, San Francisco, USA; 2Department of Neurology, University of California, San Francisco, USA; 3Colorado Division of Wildlife, Wildlife Research Center, Fort Collins, USA; 4Department of Epidemiology and Biostatistics, University of California, San Francisco, USA; 5Department of Pathology, University of California, San Francisco, USA

Background: Chronic wasting disease (CWD) of several species in the deer family and scrapie of sheep are infectious prion diseases that are transmitted naturally within affected host populations. Even though several potential sources of infectivity have been identified in secretions and excretions from symptomatic animals, the biological importance of these sources in sustaining epidemics remains unclear.

Objective/Methods: Feces from mule deer (Odocoileus hemionus) were periodically collected before and after oral inoculation with CWD prions until the deer developed clinical signs of CWD. Fecal samples were irradiated and intracerebrally inoculated into transgenic mice overexpressing cervid PrP.

Results: We report that asymptomatic CWD-infected mule deer excrete CWD prions in their feces long before they develop clinical signs of prion disease. Intracerebral inoculation of irradiated deer feces into transgenic mice overexpressing cervid PrP revealed infectivity in 14 of 15 fecal samples collected from 5 deer at 7–11 months before the onset of neurological disease. Even though prion concentrations in deer feces were much lower than those in brain tissue from the same deer collected at the disease terminus, the estimated total infectious dose excreted in feces by an infected deer over the disease course may approximate the total contained in brain tissue.

Discussion: Fecal prion excretion over long periods of time by infected deer provides a likely natural mechanism that may explain the high incidence and efficient horizontal transmission of CWD within deer herds, as well as prion transmission among susceptible cervid species.

Selected by the scientific committee from the submitted abstracts

P.4.27

Minor oral lesions facilitate CWD infection

Nathaniel Denkers1, Glenn Telling2, Edward Hoover1 1Colorado State University, USA; 2University of Kentucky, USA

Background: While the exact mechanisms of chronic wasting disease (CWD) prion transmission, entry, and trafficking remain incompletely elucidated, transmission by exposure of the oral and/or nasal mucous membranes seems certain. As part of foraging, cervids likely experience minor lesions in the oral mucous membranes; these could have impact on susceptibility to prion entry and subsequent infection.

Objectives: To explore this potential co-factor, we used cervid PrP transgenic mice to assess whether or not micro-abrasions to the tongue may enhance susceptibility to oral CWD infection. Methods: Two sets of FVB mice transgenically expressing the normal cervid PrPC protein [Tg(cerPrP) mice], with or without abrasions on the lingual mucosa, were inoculated orally with 10µl of a 10% w/v brain homogenate from either CWD-positive or negative deer. Abrasions were created by lightly scratching the dorsal lingual epithelium with a 30g needle. Cohorts were sacrificed at 1, 2, 12, 52, 78, and 104 weeks post inoculation (pi) or when signs of neurologic disease were observed. Tongue, lymphoid tissue, and the brain were assessed by western blotting and immunohistochemistry to detect the CWD abnormal prion protein (PrPCWD).

Results: Between 296 and 430 dpi, 8 of the 9 CWD-inoculated mice with lingual lesions developed clinical signs of neurologic dysfunction mandating euthanasia. The brains of all 8 mice were positive by western blot and immunohistochemistry for PrPCWD. Conversely, all mice without oral lesions remain asymptomatic at >450 dpi. No evidence of PrPCWD was detected in any Tg(cerPrP) mice examined at any of the preterminal time points.

Discussion: Micro-abrasions to the lingual surface substantially facilitate CWD transmission, suggesting a co-factor that may be significant in foraging cervids or other species. Earlier post-inoculation sampling intervals (1 and 4 hours) are in progress in an attempt to determine when and where PrPCWD might be detectable after oral mucosal exposure.

P.4.26

Aerosol and intranasal transmission of CWD

Nathaniel Denkers1, Glenn Telling2, Edward Hoover1 1Colorado State University, USA; 2University of Kentucky, USA

Background: Little is known regarding the potential risk posed by aerosolized prions. Chronic wasting disease (CWD) prions are present in saliva and urine of infected animals and it is clearly established that CWD is transmitted horizontally, almost surely by mucosal exposure. However, the potential transmissibility of CWD by aerosol or nasal routes is not known.

Objectives: The present study was therefore designed to determine whether CWD prions are transmissible by these routes of exposure using the cervid PrP transgenic mouse model of CWD infection.

Methods: FVB mice transgenically expressing the normal cervid PrPC protein [Tg(cerPrP) mice] were exposed to CWD prions by either nose-only exposure to an aerosol generated by nebulizing 0.5 ml of a 5% w/v CWD+ brain homogenate or 10µl of a 10% w/v CWD+ brain homogenate by dropwise instillation into the nostrils. Mice were monitored for signs of clinical disease for up to 755 days post inoculation (dpi). Nasal mucosa, vomeronasal organ, lymphoid tissue, and the brain were assessed for PrPCWD by western blotting and immunohistochemistry.

Results: Six of 7 aerosol-exposed Tg(cerPrP) mice developed clinical signs of neurologic dysfunction between 411 and 749 dpi mandating euthanasia. In all symptomatic mice CWD infection was confirmed by histopathologic lesions and detection of PrPCWD within the brain. Two of 9 IN-inoculated Tg(cerPrP) mice also developed TSE between 417 and 755 dpi, again confirmed by PrPCWD detection within the brain. No evidence of PrPCWD was detected in any Tg(cerPrP) mice examined at any of the pre-terminal time points.

Discussion: CWD is transmissible by aerosol as well as intranasal exposure¯potentially implicating exposure via the respiratory system in CWD and potentially other prion diseases. Studies examining very early post-inoculation sampling intervals (1 and 4 hours) are in progress in an attempt to determine initial prion targeting and entry portals.

Transmission and Pathogenesis 115

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Sunday, December 06, 2009

Detection of Sub-Clinical CWD Infection in Conventional Test-Negative Deer Long after Oral Exposure to Urine and Feces from CWD+ Deer


http://chronic-wasting-disease.blogspot.com/2009/12/detection-of-sub-clinical-cwd-infection.html






http://chronic-wasting-disease.blogspot.com/




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