Pathogenesis of experimental histoplasmosis in the bat, Artibeus lituratus

The pathogenesis of histoplasmosis was studied following intraperitoneal or intranasal infection of the neotropical bat, Artibeus lituratus. Groups of bats received either 10(4) or 10 viable mycelial fragments of Histoplasma capsulatum by intraperitoneal injection, or 10(6) or 10(4) viable mycelial particles by intranasal instillation. Intraperitoneal infection with the high dose resulted in rapid dissemination of the fungus to spleen, liver, lung and intestine, culminating in the death of some bats within 2-3 weeks. As few as 10 viable units of H. capsulatum produced systemic disease in about half of the bats, with the spleen and liver most frequently involved. In both groups the disease was characterized by gross pathologic abnormalities, numerous viable fungi in the tissue, and histologic lesions compatible with a chronic inflammatory process. Following intranasal exposure to 10(6) viable fungi, the primary pulmonary infection disseminated to the spleen, liver, and intestine within 2 weeks. Gross lesions were rarely observed in the viscera, and only one death resulted from the disease. The chronic disseminated nature of histoplasmosis in A. lituratus, especially following the more natural route of infection, suggests the means by which these bats could acquire and harbor H. capsulatum in nature. The frequent involvement of the gastrointestinal tract provides the mechanism by which these reservoirs might seed their environment with the fungus. The similarities between the pathogenesis of histoplasmosis in humans and bats provide a strong rationale for the use of this model in basic histoplasmosis research.