The most important reservoir of wildlife rabies on the American Great Plains is the striped skunk. A rabid striped skunk taken in August 1988 near Deaver, WY became the index case for a subsequent epizootic in a previously skunk rabies free area. In 1989, more rabid skunks occurred and the epizootic was moving throughout Sage Creek and in later years (1990-1993) through the entire Shoshone River basin. Federal, state, and local officials cooperated in a rabies program with the goal of addressing the health and safety of the region’s citizens, domestic animals, and livestock. Three areas of focus in the program were: 1) immunization of pets and livestock, 2) public education, and 3) skunk population monitoring and control. Rabies immunizations were re-emphasized by the local veterinarians and public health officials for pets to decrease potential rabies spillover to other species. Public education emphasized the dangers of rabies and the behavior of rabid animals using local news media and assemblies at area schools. This paper provides a synoptic overview of the third component – skunk population monitoring and control provided by USDA/APHIS’s Wyoming Wildlife Services (WS). WS provided trapping expertise starting in 1990 with rabid specimens identified by the Wyoming State Veterinary Laboratory. Starting in 1990, WS’s National Wildlife Research Center provided data analysis of rabid locations for the entire epizootic (i.e., 1988-1993). These analyses demonstrated the epizootic’s movements through the novel first use of a Geographic Information System that merged a wildlife disease (i.e., rabies) case/capture locations and dates with additional GIS data layers including hydrology, human population density, and land use. The epizootic ended in 1994 with striped skunks, bats, cats, and one horse affected. Studying this epizootic should benefit officials in planning future surveillance and/or depopulation programs. This study demonstrated the need for a skunk rabies vaccine and effective delivery system, and if the latter had been available maybe this epizootic would have been more limited in its scope and duration.

A rabies epizootic occurred in striped skunks from 1988-1993 in a previously rabies-free area of northwestern Wyoming. USDA APHIS Wildlife Services (WS) cooperated with state and local officials by providing a rabies monitoring and depopulation program starting in 1990. Wyoming WS asked for assistance in 1991 from the National Wildlife Research Center (NWRC) to analyze the epizootic’s movements. The goal was to address the public’s concerns about their health and safety and that of their domestic animals and livestock. All rabid skunks were diagnosed by the Wyoming State Veterinary Laboratory (WSVL) using standardized fluorescent antibody testing of brain tissues. The “Index Case” was collected on August 15, 1988 near Cowley. The epizootic moved radially out from this location and was limited by skunk habitat that was itself constrained by physiographic barriers. Rabies spread up and down Polecat and Sage Creeks before entering the rest of the lower Shoshone River Basin (SRB). It then moved both downstream to the Bighorn Lake and upstream toward Yellowstone National Park. However, when this epizootic ended in 1993, it had reached only the lower SRB downstream from Buffalo Bill’s Reservoir and Canyon. This area has been rabies-free ever since. Over the years various analytical techniques have been utilized by the authors to better understand and describe this epizootic. These have included: traditional county surveillance data (1988); GPS, digitized, and geocoded locations (1991); and GIS databases with and rudimentary landscape epidemiology (1992). Following the epizootic, we used more detailed GIS databases as they were developed for land cover (i.e., habitat), hydrology, and human populations from 1999 - 2006. Subsequent rabies analyses have included: movement of the monthly mean locations (2007); spatial ellipsoid movements indicating “wave fronts” or “crests” (2008); and multivariate movement maps (MMM) (2009). MMM were used to illustrate the rabies front(s) with the instantaneous and spatially described density of cases and directional flow of spreading disease. The advantages and drawbacks of each analysis tool are discussed. The evolution of these different analytical tools and their uses should assist epidemiologists in analyzing and understanding future rabies epizootics.