Prevalence of rabies in bats in Michigan, 1981-1993

Abstract

Objectives: To analyze the species distribution of animals submitted to the Michigan Department of Public Health (MDPH) for rabies testing during 1993. To determine whether any of the 9 species of bats residing in Michigan carries a disproportionate rabies burden, and to determine whether bats contributed the most cases of confirmed rabies during 1981 through 1992.

Design: Epidemiologic study.

Procedure: Records of animals submitted to the MDPH for rabies testing during 1993, and between 1981 and 1992, were reviewed. Information regarding type of animal submitted, specific species if the animal was a bat, county from which the animal was obtained, the identity of the submitting individual, species of the animal exposed, month of the submission, and results of rabies testing was extracted from these records.

Results: During 1993, the MDPH received 2,045 submissions for rabies testing. Seventeen rabid animals were identified: 1 cat, 1 skunk, and 15 bats. Two hundred forty-six bats were submitted for testing. Eptesicus fuscus, the big brown bat, accounted for 97.2% (239) of bat submissions and was the only species of bat that had positive results of testing for rabies. Annual percentages of submitted bats found to be rabid ranged from 2.0 to 11.0%, with a 13-year mean of 6.2%.

Conclusions: 100% of the confirmed cases of rabies in bats reported in Michigan in 1993 were associated with in E fuscus. During 1981 through 1992, most of Michigan's confirmed cases of rabies in animals developed in bats.