Experimental Infection of North American Insectivorous Bats (Tadarida Brasiliensis) with Histoplasma Capsulatum *

SummaryTwenty Mexican free-tailed bats (Tadarida brasiliensis) were inoculated intraperitoneally with a 6 × 106 yeast cells of Histoplasma capsulatum. Sixteen of the experimentally infected animals died of disseminated disease between the 7th and 34th days after inoculation. Postmortem pathological findings in the infected animals are described. Cultural and histopathological examination of specimens of blood, lung, liver, spleen, kidney and intestine from the dying animals were all positive for H. capsulatum. The four surviving bats were sacrificed 9–12 weeks after inoculation and all organs examined were negative on culture and histological exam.Fecal specimens from 11 of the 20 experimentally infected bats yielded H. capsulatum on culture. The fungus was recovered in feces from 10 of 12 bats surviving longer than 2 weeks, suggesting that gastrointestinal involvement occurs relatively late in the disease, probably as a result of hematogenous dissemination from a primary focus. H. capsulatum was isolated from fecal specimens of 3 of the 4 surviving animals that were culturally negative at autopsy, suggesting that Histoplasma infection in bats may not be uniformly fatal and that a self-limited form of the disease may occur. The presence of the fungus in kidneys of naturally and experimentally infected animals suggests that bats with histoplasmosis may also excrete the fungus in their urine. The possible epidemiologic and public health implications of these findings are discussed.