Epidemiologic Study of Cryptococcus neoformans

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Abstract
An epidemiologic study of cryptococcosis was conducted among a group of pigeon fanciers and a group of individuals having no contact with pigeons. A complete history, chest X ray, intradermal tests with cryptococcin, histoplasmin, blastomycin and PPD-S [purified protein derivative]; and serologic tests for cryptococcosis, histoplasmosis and blasto mycosis were performed on each person. Ths histories, chest X rays and serologic tests did not reveal any evidence of active cryptococcosis. However, 9 of 28 pigeon fanciers (32%) had positive cryptococcin intradermal tests while only 1 of 24 persons (4%) having no contact with pigeons had a positive test. Twnety-five of the 28 pigeon fanciers had C. neoformans present in their pigeon coops. The greater incidence of reactions to cryptococcin among the group with known exposure to C. neoformans is statistically significant. Absence of positive findings from medical histories and physical examinations suggests that these infections of cryptococcosis were mild or asymptomatic. The number of infections detected in this group is less than would be seen if the group were similarly exposed to other of the systemic mycoses, such as Histoplasma capsulatum. This may be attributed to lack of sensitivity of the cryptococcin antigen at a 1:100 dilution and the size of the organism, C. neoformans. These results of the cryptococcin skin test antigen merits further evaluation of this antigen as an epidemiologic tool.