A natural focus of Histoplasma capsulatum var. duboisii is a bat cave

The natural reservoir of Histoplasma capsulatum var. duboisii, the etiological agent of histoplasmosis duboisii (African histoplasmosis) is not yet known. We report the isolation of H. capsulatum var. duboisii from soil admixed with bat guano and from the intestinal contents of a bat in a sandstone cave in a rural area, Ogbunike in Anambra State of Nigeria. Eight of 45 samples of soil admixed with bat guano yielded H. capsulatum var. duboisii. Of the 35 bats belonging to the species Nycteris hispida and Tadirida pumila examined, only one (N. hispida) yielded this fungus from its intestinal contents. Identification of the isolates as Histoplasma was confirmed by exoantigen tests and by mating with tester strains of H. capsulatum. In vitro conversion to large yeast from suggestive of H. capsulatum var. duboisii was obtained on brain heart infusion agar supplemented with sheep blood and glutamine or cysteine. Pathogenicity tests with mice for all the isolates confirmed their identity by the demonstration of large yeast forms (8-15 microns in diameter) within giant cells in the infected tissues. Investigations on the possible occurrence of human infections in the area are in progress.