Dermatophytosis in domestic animals is a superficial cutaneous mycosis commonly caused by fungi of the genus Microsporum and Tricophyton. It mainly affects cats, horses and dogs, even if less frequently.
In immunocompetent animals the infection is often self-limiting, but different factors and conditions, such as FIV cats or puppies, as well as young or old dogs, animals living in conditions of overcrowding or under cortisone therapy can favour the clinical onset and the spread of the disease. Persian cats and Yorkshire terrier dogs seem to be more susceptible to infection.
Dermatophytes are transmitted by direct contact with an infected animal. Since spores are very environment resistant (months or years), indirect infection is also possible through the contaminated environment.
Dermatophytes can metabolize keratin, which they feed on, and grow on the horny layer of the skin and nails and in the horny keratinized layer of the hair follicle.
Typically, lesions occur as focal or multifocal alopecia areas of circular or irregular shape with desquamation and crusting. On the edge of the affected area, papules or follicular pustules are frequently present. Itch is generally absent. However, it may also intense in some subjects.
Dermatophytosis in cats can be asymptomatic, i.e. no clinical lesions are present, but cats remain carriers. Clear lesions are more easily observed in young subjects on the face, auricles and limbs, while in adults there may be more or less itching miliary dermatitis. In Persian cats, the formation of subcutaneous nodules (pseudo-micetomas) is possible.
Dermatophytosis in dogs occurs with multifocal alopecia areas and kerion (nodular reactions involving the dermis with alopecia and exudative ulcers usually located on the face). Dermatophytosis is a zoonosis, it can be transmitted to humans and causes skin lesions. The development of clinical forms in humans depends on many factors, including individual sensitivity, duration of the contact between the person and the animal. Also immunodepressed and young subjects may be predisposing factors. Dermatophytosis is clinically similar to other skin diseases. A diagnostic confirmation is important before the antifungal treatment gets started to avoid problems for the owners.