The Association of a Bird-Roosting Site with Infection of School Children by Histoplasma Capsulatum

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Abstract
Epidemiologic studies were done to determine the location of a point source of Histoplasma capsulatum responsible for a situation best described as hyperendemic sensitivity to histoplasmin in children attending school in Milan, Michigan, in 1958. These studies pointed to the soil of the unpaved backyard of a school building and under a line of trees which formed part of a prominent starling (Sturnis vulgaris) roost. Soil samples, representing the entire community, were collected. A random sample of these was tested for the presence of H. capsulatum by an indirect method utilizing the injection of aqueous extract of soil intraperitoneally into mice with subsequent culture of mouse liver and spleen fragments on artificial media. The fungus was isolated from 16 of 184 soil samples; all 16 positive soils came from within the limits of the starling roost area. It was concluded that the high prevalence of positive histoplasmin tests, 61% of school children, was best explained as due to the sharing of an environmental niche, the school yard, by large numbers of children and starlings; the trees provided a roost for the birds and temperature and moisture control for the soil beneath; the birds provided through their droppings some substance (s) of selective advantage to the fungus for its growth; the fungus growing in the soil produced spores which were disseminated in the dust; children using the grounds as a play area stirred up dust and became infected through inhalation of the spores.