Clinical Presentation and Serologic Response during a Rabies Epizootic in Captive Common Vampire Bats (Desmodus rotundus)

We report mortality events in a group of 123 common vampire bats (Desmodus rotundus) captured in Mexico and housed for a rabies vaccine efficacy study in Madison, Wisconsin. Bat mortalities occurred in Mexico and Wisconsin, but rabies cases reported herein are only those that occurred after arrival in Madison (n = 15). Bats were confirmed positive for rabies virus (RABV) by the direct fluorescent antibody test. In accordance with previous reports, we observed long incubation periods (more than 100 days), variability in clinical signs prior to death, excretion of virus in saliva, and changes in rabies neutralizing antibody (rVNA) titers post-infection. We observed that the furious form of rabies (aggression, hyper-salivation, and hyper-excitability) manifested in three bats, which has not been reported in vampire bat studies since 1936. RABV was detected in saliva of 5/9 bats, 2-5 days prior to death, but was not detected in four of those bats that had been vaccinated shortly after exposure. Bats from different capture sites were involved in two separate outbreaks, and phylogenetic analysis revealed differences in the glycoprotein gene sequences of RABV isolated from each event, indicating that two different lineages were circulating separately during capture at each site.