Development of an experimental model of Microsporum canis infection in cats.

An experimental infection model was developed for reliable induction of Microsporum canis skin infections in cats, using a defined number of macroconidia harvested from the fungus in culture. The strain of M. canis used produced highly fluorescent hairs under ultraviolet illumination. Kittens 8 to 9 weeks of age (n = 6) received 10(5) macroconidia applied topically to a closely-shaved area of skin. Sites were dressed with an occlusive bandage for 3 days, then grooming was restricted for an additional 4 weeks. Lesions were first observed 2 weeks after inoculation, enlarged over the following 6 to 8 weeks, then decreased in size and appeared healed at 12 to 14 weeks after inoculation. Cats often developed satellite lesions on the face, ears, or other body regions. The experimental infections strongly resembled moderately severe cases of naturally-occurring feline dermatophytosis in clinical patients. This experimental infection model will be useful for evaluation of topical and systemic treatments for feline M. canis infection.