Presence of rabies neutralizing antibodies in wild carnivores following an outbreak of bovine rabies.

In an outbreak of bovine rabies in Argentina, a study was made of vampire bats (Desmodus rotundus) and wild carnivores. Rabies antibody rates of high prevalence were found in the bats, foxes (Dusicyon gymnocercus) and skunks (Conepatus chinga). The outbreak was part of an extensive continuing epizootic of vampire transmitted bovine rabies which may have also involved other vectors in the area of this study. Consumption of dead and dying bats by the carnivores is the suggested means of passage of rabies virus from vampire bats to foxes and skunks. Given optimum conditions it is conceivable that some outbreaks in carnivores may begin in this way.

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.