Prevalence of Cryptococcus Neoformans in Pigeon Habitats

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Abstract
Virulent strains of Cryptococcus neoformans are generally present in pigeon manure in old pigeon nests and under roosting sites. Recent additional isolations of this pathogenic fungus from varied types of rural and urban environments are reported. The frequent occurrence of_C. neoformans in man''s environment presents a hazard not recognized prior to 1955. Histoplasma capsulatum has not been isolated from pigeon manure on upper floors of buildings. This fact, the equivocal results of serologic tests, and the circumstances associated with isolation of H. capsulatum in certain epidemics of pneumonitis provide strong presumptive evidence that these were epidemics of a previously unrecognized form of cryptococcosis and that the retrospective diagnosis of histoplasmosis was erroneous. C. neo-formans is very frequently present in pigeon manure from haymows in barns and from upper floors of buildings which have sheltered pigeons. In view of these facts, the circumstantial evidence for a diagnosis of a previously unrecognized pulmonary form of cryptococcosis is as strong as the circumstantial evidence for a diagnosis of histoplasmosis in certain past epidemics of pneumonitis in men who were exposed to pigeon manure while demolishing old buildings which had sheltered pigeons. Until such epidemics can be studied systematically at the time they occur, instead of in retrospect, and until cultures and adequate serologic studies are made, the etiology of the type of pneumonitis reported will remain equivocal.