Studies on the Pathogenesis of Rabies in Insectivorous Bats: III. Influence of the Gravid State

The present study concerns the influence of the reproductive cycle on experimental rabies infection in the Mexican free-tailed bat (Tadarida b. mexi-cana). A method was devised whereby it was possible to determine by fetal weight alone that the bats within each experimental group were in approximately the same stage of pregnancy and that groups in progressive stages in the reproductive cycle were used in these experiments.Susceptibility of bats to intramuscular inoculation of rabies virus did not appear to be altered significantly during the gestation period. Evidence of transplacental transmission of rabies virus was obtained, and virus was isolated from mammary gland tissue of experimentally infected bats.Variations were noted in the frequencies of isolation of virus from the brown adipose tissue of experimentally infected bats in different stages of pregnancy. The influence of physiologic alterations occurring in the gravid bat on rabies virus multiplication in brown adipose tissue is discussed.