A retrospective study of Trichophyton mentagrophytes infection in dogs (1970-2002)

In the 33-year period from 1970 to 2002, 3854 dogs with different dermatological disorders were examined at the Department of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, University of Zagreb, Croatia. Clinical and laboratory examinations of all skin and hair samples yielded 66 (1.7%) isolates of Trichophyton mentagrophytes, while Microsporum canis was diagnosed in 840 cases (21.8%). Other dermatophytes were cultured less frequently. Microsporum gypseum was isolated in 38 dogs (1.0%), while Microsporum persicolor was diagnosed only twice (0.1%). A retrospective study of trichophytosis due to T. mentagrophytes was performed in order to present different clinical aspects in dogs. All 66 dogs showed clinical evidence of skin lesions, and four groups with different symptoms were identified. The majority of dogs 42 (63.6%) with T. mentagrophytes infection had lesions typical of dermatophyte infection. The remaining 24 dogs (36.4%) were without nummular lesions typical of dermatophyte appearance. The clinical picture included multifocal to diffuse appearance in 12 dogs (18.2%), severe inflammatory lesions in 10 (15.2%) or granulomatous lesions resembling pseudomycetoma in 2 dogs (3.0%). Considering the veterinary and public health importance of canine ringworm, attention was focused on T. mentagrophytes due to variations in clinical appearance which might make early diagnosis very difficult, together with duration of infection and reappearance due to persisting spores.