An outbreak of phaeohyphomycosis in rainbow trout caused by Scolecobasidium humicola.

A previously undescribed host for the opportunistic dematiaceous hyphomycete, Scolecobasidium humicola, is reported. Several epizootics among rainbow trout, Salmo gairdneri, occurred in a Tennessee fish hatchery from 1969 to 1973. Symptoms included surface lesions, blisters and abscesses. The kidneys and other internal organs were invaded by the mycelium of S. humicola. Tissue morphology of the fungus was typical of that associated with phaeohyphomycosis Experimental infections were reproduced in fingerling rainbow trout after intraperitoneal inoculation of S. humicola. Following a change in the hatchery's water supply, no new epizootics have occurred.