Characteristics of rabies in bats in Montana.

Abstract

SINCE the isolation of rabies virus from a bat in western Montana in the late summer of 1954, bats of all species known to occur in Montana, except the rare Euderma maculata and Myotis subulatus,' have been collected and examined for rabies virus. Species examined thus far include2 Eptesicus fuscus, Myotis californicus, Lasiurus cinereus, Lasionycteris noctivagans, Myotis evotis, Myotis volans, Myotis yumanensis, Myotis lucifugus, and Corynorhinus (Plecotus) townsendii. Most of the animals were from the Bitterroot Valley in southwestern Montana, but a few specimens were submitted from various other areas of Montana. Rabies virus was recovered by technics described in the following and the ability of bats to transmit infection by bite was demonstrated.3 Behavior of rabies-infected bats ranged from apparently normal to actively aggressive, but the majority of animals were found in circumstances that were aberrant and even suggestive of rabies. Although only two of the 21 infected bats collected bit human beings and in only one instance could the attack be considered unprovoked, belligerence was evident in several instances. In one instance a bat was flying at children and dogs; in another, two bats were fighting viciously and the survivor was rabid. On three occasions bats were taken away from cats and a dog but the aggressor in these cases was unknown. The dog and cats did not become ill during close observation for six months. One apparently normal, but infected, Eptesicus kept in a captive colony for 30 days after capture did not infect four other Eptesicus kept with it. Rabid bats are much more likely than normal bats to come to the close attention of man. This is especially true of solitary bats that normally lead rather obscure lives. Seyeral thousand bats, most of them colonial, have been examined. Although only a few individuals of some species have been encountered, the incidence of rabies in them has been unusually high, suggesting that illness was responsible for their discovery. For example, only one Lasiurus cinereus was obtained, and it was rabid. Myotis californicus was found; singly and in groups on four occasions and two bats of this species were rabid. The species had not been recorded previously in Montana. Myotis volans was found only three times and one specimen was rabid. Six Lasionycteris noctivagans were submitted one year and three the next year; the first three examined were infected. Infrequency of encounters with normal bats of the above species does not necessarily indicate rarity, but may reflect habits and habitats that do not ordinarily bring them into contact with man. There was usually some evidence of irritability and willingness to bite and this seemed to be an accentuation of normal disposition. The normally more surly Lasionycteris and Eptesicus were more vicious than the smaller and