C00007Surveillance for Chronic Wasting Disease: Methods to Determine Prevalence and Distribution in Free-ranging Cervids
M. W. Miller (1), and E. S. Williams (2)
(1) Colorado Division of Wildlife, Fort Collins, CO and (2) University of Wyoming, Laramie, WY
Abstract:
Chronic wasting disease (CWD) is a spongiform encephalopathy of mule deer Odocoileus hemionus, white-tailed deer O. virginianus, and Rocky Mountain elk Cervus elaphus nelsoni found in northcentral Colorado and southeastern Wyoming. To understand epizootiology of CWD, to determine its distribution, and to reliably model its dynamics and effects on wild populations, methods for efficiently and effectively surveying free-ranging populations of deer and elk are needed. Active surveillance of free-ranging cervids in the endemic areas began in 1981, but has been more intense since 1992. Two strategies are currently being employed in the endemic areas of Colorado and Wyoming, as well as many other states and provinces in western North America, to survey for CWD: 1) Recognition, collection, and submission of suspect CWD cases to veterinary diagnostic laboratories by wildlife agencies. The CWD (suspect) profile includes deer or elk; >=18 months of age; emaciated and showing abnormal behavior, and/or increased salivation, and/or tremor, stumbling, incoordination, and/or difficulty in swallowing, and/or polydipsia/polyuria. Using this approach, 78 CWD-positive cervids were identified in the five county endemic area in Colorado and Wyoming since 1981; at least 268 additional (suspects) submitted from throughout Colorado and Wyoming were also examined and found to be affected by other maladies. 2) Collections of heads (or brain stem and tonsils) from harvested deer and elk via check stations or specified drop-off points. Brains were examined by histopathology, and beginning in 1995, by immunocytochemistry; selected cases were also examined for SAF and by Western blot analysis. Estimated prevalences from harvest surveys were <1.1% in elk (1992-1996; n=337) and about 2.5% (1983-1996; n=687; range 0-5.9% annually) in endemic areas; none of >300 samples from cervids harvested outside endemic areas were positive. Based on results obtained to date, we believe this combination of extensive clinical surveillance and intensive population sampling represents an effective and efficient strategy for studying and monitoring CWD in free-ranging cervid populations.
Comments:
Address questions and comments about this abstract to Beth Williams ( storm@uwyo.edu).