Observations on the epizootiology of vampire bat rabies.

Vampire bat populations were opportunely sampled before, during, and at varying intervals after outbreaks of bovine rabies. The captured bats were examined for rabies neutralizing antibody and virus. In all, sera from 1,024 vampire bats were tested for antibody, and tissues from these bats plus 83 others were tested for virus. Neutralizing antibody only rarely appeared in vampire serum samples taken before bovine rabies outbreaks, and only low percentages of samples positive for rabies antibody were obtained from bats captured during bovine outbreaks. In contrast, varying percentages of positive samples (including some high percentages) were taken from bats captured at various intervals after bovine outbreaks. Only eleven rabies virus isolations were obtained in the course of this study. In each case the virus came from a bat captured just before or during a bovine outbreak. The authors suggest that rabies virus behaves in vampire populations the way diverse infectious agents typically behave in other hosts. That is, the virus infects many individuals; some die and others survive to demonstrate their exposure through the appearance of anitbody. The disease disappears from the bat population in time and does not return until a sufficient number of susceptible bats have re-entered the population.