Trends in national surveillance for rabies among bats in the United States (1993-2000)

Objective-To describe surveillance trends and epidemiologic features of. rabies in bats in the United States, focusing on 3 bat species primarily associated with variants of the rabies virus that affect humans. Design-Retrospective study. Animals-31,380 bats. Procedure-Data on rabies for bats identified to species and reported by state laboratories from 1993 to 2000 were analyzed, focusing on silver-haired, eastern pipistrelle, and Brazilian free-tailed bats. Categoric variables were derived from other provided information. Results-Data were reported from 37 states during the study interval; complete species-specific data were not reported by any state for the entire interval. Bats primarily associated with rabies virus variants affecting humans were more likely to yield positive test results for rabies. (22.7%), compared with all other bats (5.5%) in most seasons and from most regions of the United States. However, certain other bat species had higher percentages of positive results. Risk of positive results was highest in the fall and highest among bats originating in the southwestern United States. Conclusions and Clinical Relevance-Increased risk of rabies among certain groups of bat species was consistently found, across seasons and most geographic regions of the United States. Results were in general agreement with those of previous studies conducted within smaller geographic regions. There,are ongoing efforts to improve surveillance of rabies in bats, although surveillance is incomplete in some regions.