Spontaneous dermatophytosis due to Microsporum canis in rabbits.

Reports of naturally occurring Microsporum canis infection in the rabbit are rare. During the tenth week of a 91 day percutaneous toxicity study, 17 of 30 adult New Zealand white rabbits developed skin lesions varying from multiple papules to ringed lesions 1 X 2 cm in diameter. The lesions were not pruritic. Hair and scale samples taken from rabbits with lesions were cultured for dermatophytes. Based upon colony morphology and macroconidial characteristics, M canis identification was confirmed. At the time of necropsy, fluorescence was observed in three animals examined with a Wood's lamp, and of 10 rabbits that were positive on culture, seven were clinically normal. Microscopically, hair follicles contained spores and mycelia. The source of this outbreak was not determined. Tap water was cultured and found negative for pathogenic fungi. These findings document M canis infections in laboratory-housed New Zealand white rabbit, such an asymptomatic carrier state should be considered in this outbreak. The significance of dermatomycosis in laboratory animals is primarily as a zoonosis and a research complication.