Ringworm Infection in Dogs and Cats (24-Jun-2003)

Introduction Keratinophylic fungi are common inhabitants of the soil, where they process the hairs and skin cells shed by animals, as well as all types of keratin products that fall from animals and humans during the natural and continuous cycle of skin and coat shedding. The group of keratinophylic fungi is very large, but only three genera, known as dermatophytes, are known to cause disease ("ringworm") in animals and humans. The three genera involved are Microsporum, Trichophyton and Epidermophyton; the first two are most frequently found in animals while the third causes problems mainly in humans [1]. Ringworm is of importance not only because it can cause skin disease in dogs and cats, but it also can be transmitted to other animals as well as to humans. The particular ability of these three genera to be transmissible to animals, as well as to humans, signifies that they are an important, yet poorly understood, veterinary and human health problem worldwide [2]. A classification for dermatophytes based on their habitat was proposed in 1954 [3]. In a large survey of skin samples from animals and humans, dermatophytes were divided into three groups: zoophylic those found mainly in animals, but transmitted to other animal or to humans; anthropophylic those found mainly in humans and transmitted amongst humans, but very seldom to animals; and geophylic dermatophytes found mainly in soil that infect both humans and animals. This classification is still employed by many authors [4-6] because it helps to clarify the sources of a ringworm infection. Presently, it is known that virtually all dermatophytes are geophylic and that soil is the source of most infections [7].