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Title: Chronic wasting disease in a Wisconsin white-tailed deer farm

item HALL, S
item O'Rourke, Katherine

Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2008
Publication Date: 9/2/2008
Citation: Keane, D.P., Barr, D.J., Bochsler, P.N., Hall, S.M., Gidlewski, T.E., O'Rourke, K.I., Spraker, T.R., Samuel, M.D. 2008. Chronic wasting disease in a Wisconsin white-tailed deer farm. Journal of Veterinary Diagnostic Investigation. 20(5):698-703.

Interpretive Summary: Chronic wasting disease is a fatal disease of deer and elk. Clinical signs, including weight loss, frequent urination, excessive thirst, and changes in behavior and gait, have been reported in mule deer and elk with this disorder. Clinical signs in captive white tailed deer are less well understood. In a previous study, a captive facility housed 200 deer, of which half were positive for the disease with no clinical signs reported. In this study, we examined 78 white tailed deer from a captive facility with a history of chronic wasting disease and no animals with clinical signs. Examination of the brain and lymph nodes demonstrated that the abnormal prion protein, a marker for disease, was observed in 60 of the deer. Biopsy of the rectal mucosa, a test that can be performed on live deer, detected 83% of the infected animals. The prion genetics of the deer was strongly linked to the rate of infection and to disease progression. The results demonstrate that clinical signs are a poor indicator of the disease in captive white tailed deer and that routine testing of live deer and comprehensive necropsy surveillance may be needed to identify infected herds.

Technical Abstract: Chronic wasting disease CWD is a transmissible spongiform encephalopathy or prion disease of deer and elk in North America. All diseases in this family are characterized by long preclinical incubation periods following by a relatively short clinical course. Endpoint disease is characterized by extensive deposits of aggregates of the abnormal prion protein in the central nervous system,. In deer, the abnormal prion proteins accumulate in some peripheral lymphoid tissues early in disease and are therefore suitable for antemortem and preclinical postmortem diagnostics and for determining disease progression in infected deer. In this study, a herd of deer with previous CWD diagnoses was depopulated. No clinical suspects were identified at that time. Examination of the brain and nodes demonstrated that 79% of the deer were infected. Of the deer with abnormal prion in the peripheral lymphoid system, the retropharyngeal lymph node was the most reliable diagnostic tissue. Biopsy of the rectal mucosal tissue, a site readily sampled in the restrained or chemically immobilized deer, provided an accurate diagnosis in 83% of the infected deer. The retina in the eye of the deer was positive only in late stage cases. This study demonstrated that clinical signs are a poor indicator of disease, supports the use of the retropharyngeal lymph node as the most appropriate postmortem sample, and supports a further evaluation of the rectal mucosal tissue biopsy as an antemortem test on a herd basis.