Wildlife Damage Management, Internet Center for


Date of this Version

April 1995


In 1994, 2 ongoing rabies epizootics were declared a state health emergency: canine rabies in South Texas and gray fox (Urocyon cinereoargenteus) rabies in West-Central Texas. Prior to 1988, rabid coyotes (Canis latrans) were infrequently reported in Texas. In 1988, Starr and Hidalgo counties, located in extreme South Texas, experienced an epizootic of canine rabies resulting in 11 laboratory-confirmed cases of canine rabies in domestic dogs (Canis familiaris) and 6 cases in coyotes. By 1991, the epizootic had expanded approximately 160 km north of the United States (US)-Mexico border and included 10 counties. During the next 3 years, 8 additional counties became involved in the epizootic as it continued to move northward. During the 7- year-period, there were 531 laboratory-confirmed cases of canine rabies in 18 counties, and the epizootic was 255 km north of the US- Mexico border at its furthest extent. Gray fox rabies, which was endemic in West-Central Texas, also became epizootic in 1988. It began in Sutton County and rapidly expanded to include 6 additional counties by the end of the year with 23 laboratory-confirmed cases of gray fox rabies. From 1989 to 1994, a range of 1 to 13 new counties per year had recorded confirmed gray fox rabies cases. It had spread approximately 130 km northward and 225 km eastward from the index case. By the end of 1994, the epizootic included 35 counties in West-Central Texas with 524 laboratory-confirmed cases of gray fox rabies. Antigenic and genetic analysis revealed the ecotype primarily affecting domestic dogs and coyotes in South Texas to be urban Mexican dog and the rabies ecotype primarily affecting gray foxes in West-Central Texas to be Texas fox. The epizootics are approaching large metropolitan areas; an increase in vaccination levels of domestic animals would help provide a barrier between rabid wild animals and humans.