Histoplasmosis is reviewed with regard to etiology, epidemiology, pathology, diagnostic criteria, methods of prevention, and research needs. Histoplasmosis is defined as a systemic fungal infection caused by the soil fungus Histoplasma-capsulatum. The organism is most heavily concentrated in the central United States, and more than 90 percent of the residents of the Ohio, Mississippi, and Missouri river valleys were shown to have evidence of being infected. Persons having close contact with the soil, particularly soil enriched with avian and bat feces, have been identified as being at high risk. Occupations at risk include farmers, bird handlers, construction workers, landscapers, earth movers, and workers involved in the cleaning or dismantling of contaminated buildings. The clinical manifestation of the primary acute disease is minimal in 95 percent of persons infected. Progressive disseminated histoplasmosis ia rare except in individuals at the extremes of age or immunologically compromised persons. Chronic progressive pulmonary histoplasmosis ia uncommon unless significant cavitation is evident. The chronic cavitary disease, left untreated, results in progressive pulmonary disability and death in 50 percent of affected persons within 5 years. Progressive pulmonary histoplasmosis occasionally results from excessive fibrosis of the lungs and lymph nodes.
Occupational Respiratory Diseases. J. A. Merchant, Editor; Division of Respiratory Disease Studies, Appalachian Laboratory for Occupational Safety and Health, NIOSH, U.S. Department of Health and Human Services, DHHS (NIOSH) Publication No. 86-102