The Production of Experimental Dermatophyte Lesions in Guinea Pigs

Experimental dermatophytoses were induced in virgin and previously infected guinea pigs by the quantitated application of spores to plucked and shaved areas of skin. Lesions could be consistently induced without occlusion with 7 dermatophytes—Trichophyton mentagrophytes, T. rubrum, T. tonsurans, Microsporum canis, M. gypseum, M. persicolor and Epidermophyton floccosum. The progress of lesions was monitored visually and their infectivity determined using a hair brush sampling technique. Airborne spread of fungal elements from infected animals to other animals housed in the same area and to the atmosphere was also examined. With 2 dermatophytes, T. mentagrophytes and M. canis, it was found that the infectivity of lesions correlated well with the clinical progress of the disease after primary infection and on reinfection. This was not the case with the other fungi investigated where factors such as absence of hair invasion, hair invasion wholly or mainly endothrix in nature, or the development of a thick scab which trapped hairs and fungal elements, resulted in the development of lesions of low infectivity. Dissemination of spores into the air and onto neighboring noncontact animals occurred readily with M. canis, and to a lesser degree with T. mentagrophytes. Airborne spread of fungal elements from lesions due to the other dermatophytes was negligible. On reinfection, some spores germinated and hyphal growth occurred but lesions appeared earlier, healed more rapidly and were markedly less infective. This experimental model with T. mentagrophytes, would seem an ideal system for investigating the effects of various procedures, e.g., antimycotic therapy, vaccination, on the progress and infectivity of dermatophyte lesions