Laboratory-acquired Coccidioidomycosis

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Abstract
Outside the endemic area in the southwestern USA coccidioidomycosis occurs primarily in laboratory workers, and is undoubtedly often asymptomatic and unrecognized. A unique opportunity for the study of laboratory-acquired coccidioidomycosis was afforded by the long term observation of a group of personnel in a large laboratory in Maryland working with the microorganism. During an 18 year period from 1944 to 1962, 2013 employees received skin tests with coccidioidin. Rapid safety precautions resulted in a minimum of recognized laboratory exposures to Coccidioides immitis. Nevertheless, six proven cases of coccidioidomycosis occurred. Of the 1895 persons who were coccidioidin-negative on initial skin test, 210 (10.4%) subsequently developed positive skin tests. Many of these individuals were considered to be in a low-risk exposure category. Correlation of coccidioidin and histoplasmin skin sensitivity indicated that the coccidioidin positive tests were not a result of cross-reactions with histoplasmin. Because of potential occupational hazards all workers were carefully observed during even minor illnesses. 147 (69.9%) of the 210 converters had no significant illnesses other than minor upper respiratory infections or transient skin rashes preceeding conversion of the skin test. 40 persons (19.0%) experienced an influenza-like syndrome and 18 persons (8.5%) had transient pulmonary findings or episodes of pneumonia possibly representing a coccidioidal infection. Of the 6 proven clinical cases of coccidioidomycosis 3 were pulmonary and 3 cutaneous (of particular interest since unequivocal primary cutaneous cases have rarely been reported). One of them had associated osteomyelitis and occurred in an individual who was skin test-positive (and therefore presumably "immune") at the time of exposure. Skin test conversion rates were highest in individuals involved in overt laboratory accidents, and most of the clinically recognized cases were in this group.

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