Surveillance for Transmissible Spongiform Encephalopathy in Scavengers of White-Tailed Deer Carcasses in the Chronic Wasting Disease Area of Wisconsin

Abstract

Chronic wasting disease (CWD), a class of neurodegenerative transmissible spongiform encephalopathies (TSE) occurring in cervids, is found in a number of states and provinces across North America. Misfolded prions, the infectious agents of CWD, are deposited in the environment via carcass remains and excreta, and pose a threat of cross-species transmission. In this study tissues were tested from 812 representative mammalian scavengers, collected in the CWD-affected area of Wisconsin, for TSE infection using the IDEXX HerdChek enzyme-linked immunosorbent assay (ELISA). Only four of the collected mammals tested positive using the ELISA, but these were negative when tested by Western blot. While our sample sizes permitted high probabilities of detecting TSE assuming 1% population prevalence in several common scavengers (93%, 87%, and 87% for raccoons, opossums, and coyotes, respectively), insufficient sample sizes for other species precluded similar conclusions. One cannot rule out successful cross-species TSE transmission to scavengers, but the results suggest that such transmission is not frequent in the CWD-affected area of Wisconsin. The need for further surveillance of scavenger species, especially those known to be susceptible to TSE (e.g., cat, American mink, raccoon), is highlighted in both a field and laboratory setting.

Acknowledgements

We thank E. Berkley, J. Hann, M. Meade, C. Nebur, A. Powers, J. Sontag, M. St. Martin, and S. Wright for field and laboratory assistance. K. O'Rourke and R. Rubenstein provided monoclonal antibodies for Western blot analysis. We also thank IDEXX Laboratories (Westbrook, ME) for financial and technical support in the use of their products. We thank the Wisconsin Veterinary Diagnostic Laboratory for necropsy and testing support and the USGS National Wildlife Health Center for funding and necropsy support. Funding was provided by the U.S. Geological Survey. We thank the Wisconsin Department of Natural Resources for logistical support. We benefited from the support and collaboration of the Wisconsin Trappers Association. Mention of trade names or commercial products does not imply endorsement by the U.S. government. The Max McGraw Wildlife Foundation provided support for publication.