Knowledge of Bat Rabies and Human Exposure Among United States Cavers

Robert V. Gibbons, Robert C. Holman, Stephen R. Mosberg, and Charles E. Rupprecht

Disclosures

Emerging Infectious Diseases. 2002;8(5) 

In This Article

Conclusions

Despite the cavers' education level and their familiarity with bats, 14% of the cavers did not consider a bat bite risk for rabies. When only the cavers without a college degree were considered, 26% did not think a bat bite was a risk for rabies. Given the general public's assumed education level and overall lack of familiarity with bats, the percentage of the public who do not consider a bat bite a risk for rabies is probably higher than (or closer to) 26%, than 14%. If so, this would support the hypothesis that people may lack the knowledge to seek medical care if a bat bites them. Unlike bites from larger mammalian carnivores, lesions resulting from a bat bite probably will not warrant seeking medical care. In addition, 39% of cavers did not think a bat scratch was a risk for rabies. Technically, a scratch contaminated with saliva is an exposure, but scratches alone are less likely to transmit rabies than a bite. The practical problem arises in the consideration of scratches from bats. Does the patient know if the scratch is contaminated with saliva? And more importantly, can a patient discern a scratch from a bite, particularly under the darkened and tight recesses of a cave?

Eleven percent of cavers felt that indirect contact with bats to be risk for rabies. Some cavers (especially older, more experienced members) may possess knowledge of those rare cases of human rabies that are attributed to aerosol transmission. Two infections in the 1950s, commonly attributed to aerosol transmission in crowded bat caves (in a bat researcher and a mining engineer), had other possible mechanisms of infection[7,8], and no other infections have been reported in cavers. Interestingly, the lack of rabies cases in cavers is evidence against the occurrence of aerosol transmission, except under extraordinary circumstances. The respondents in our study, if projected to only cavers who are members of the NSS, represent over 4 million caving episodes; nearly 60% involved cavers with no PreEP. Of course, the expected prevalence of rabies in freeranging bats is low, probably <1%[9].

This survey is limited by a low response rate and may be subject to selection bias. Those who did respond may be more or less familiar with rabies than the average caver. In addition, the survey may be subject to response bias. Relationships demonstrated are associations; cause and effect cannot be definitively determined.

Nevertheless, our study suggests that despite longstanding guidelines for cavers to receive PreEP for rabies, only 20% have done so. The increase is modest when compared to a survey conducted in 1970 of 239 cavers, which found that only 14% had received PreEP (CDC, unpub. data). Increasing the cavers' awareness about the recommendation may increase compliance, as 64% of those advised to receive PreEP had done so, compared to 6% (n=19) of those not advised to do so. In fact, this was the only independent predictor of receiving PreEP. A future survey of the general public is indicated to explore their knowledge and attitudes towards bats, rabies, and the risk for acquisition.

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