Experimentally induced Histoplasma capsulatum infection in coyotes and a dog

Captive coyotes (Canis latrans) were inoculated intragastrically (1 coyote), and intratracheally (6 coyotes) with Histoplasma capsulatum to simulate natural routes of exposure. In addition, the infectious organism was inoculated IV into another coyote and into a dog (C familiaris) to simulate hematogenous dissemination of H capsulatum. Isolation of the pathogen from various tissue specimens, using direct plating and mouse inoculation methods, provided mycologic evidence of infection. The presence of anti-Histoplasma serum antibodies also was monitored. Of the 6 coyotes challenged intratracheally, one developed a benign pulmonary form of histoplasmosis. This coyote developed a transient cough, and intracellular yeasts typical of H capsulatum were observed microscopically in pulmonary tissue specimens. The pathogen was isolated from specimens of pulmonary tissue and associated lymph nodes. The coyote that was fed Histoplasma-infected mice (intragastric challenge) did not develop clinical disease. The coyote and the dog inoculated IV developed a multifocal, nonsuppurative infection, without clinical evidence of histoplasmosis. Pathologic findings in the coyote and dog were similar; both animals had splenitis, lymphadenitis, and petechiation of the lungs. The liver and spleen were considered the primary extrapulmonary target organs on the basis of mycologic and histologic findings.