Dermatophytosis is a fungal infection of the skin commonly called "Ringworm".  Both dogs and cats are susceptible to the three species of fungi which commonly cause ringworm. The dermatophyte infection grows in a circular fashion and the center of the lesion often begins to heal causing the classic ringworm lesion.

Dermatophytes live in the soil, on animals and on people. Pets can acquire a dermatophyte infection from any of these sources and pass the infection on to other pets or to people.

In dogs, dermatophytosis is characterized by areas of hair loss (alopecia) and scaling.  These areas are typically well demarcated and may be numerous.  Young and immune-compromised dogs tend to have more severe lesions.  Rarely, dermatophyte infections become generalized and hair loss and scaling may be widespread.  In cats, dermatophyte infection may take many forms.  In both dogs and cats, dermatophytosis lesions are commonly secondarily infected with Staphylococcus intermedius.

Diagnosis of dermatophytosis based on clinical signs and culture of the organisms from skin
scraping.  These organisms are slow growing and final diagnosis may take up to 21 days.  Occasionally, the lesions may fluoresce under a black lamp.

Treatment choice is based on the extent of lesions and the health status of the patient.  Often all that is necessary is clipping the affected areas combined with topical therapy.  With wide spread lesions and in cats,  systemic therapy is usually instituted in addition to topical medications.  Occasionally, dermatophyte infections will resolve spontaneously but, due to the infectious nature of the infection, it is advisable to treat all suspected dermatophyte infections.

In addition to medical treatment, it is important for you to wash your hands after handling your pet.  Avoid contact between your pet and children and other animals.  Please contact your veterinarian if you are not able to medicate your pet as instructed or if your pet develops new areas of infection.