Direct Exposure of Mice to Soils Known to Contain Histoplasma capsulatum.

Abstract

Suscep-tibility of white Swiss mice to infection with Histoplasma capsulatum by inhalation of dust aerosol was determined by direct exposure of animals to known positive soil samples. Disseminated histoplasmosis occurred in a large percentage of the exposed mice. Naturally contaminated soil samples held 5 and 10 months, at room temperature, remained highly infectious. Artificially-seeded soil cultures were 100% infective to white mice at exposure of 1, 2, 4, and 7 days. The safety hood and associated safety procedures proved completely effective in preventing infection of the control mice, although the controls were placed in close proximity to animals exposed to known positive soil samples. The results of these studies add support to the hypothesis that man and animals become infected with H. capsulatum by the respiratory route.