Dermatophytosis, more commonly known as “ringworm”, is an infectious skin condition that affects both dogs and cats. It is a frustrating issue many pet owners in the region encounter due to its difficulty to definitively diagnose, lengthy treatment protocols, and potential contagion to pet parents. The classical skin lesion is a circular red raised area of hair loss that may progress quickly to multiple sites around the body.
Many find the common name misleading, because ringworm is not technically a worm. Dermatophytosis is a fungal infection of the skin and hair follicles. There are three types of dermatophytes that commonly infect our pets: Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes. Each is contracted by contact with the fungus within the environment, other infected animals, or by fomites shared between animals. Typically there is a 2-4 week period between contracting the infection and showing clinical lesions. The animals may, however, be infectious to others during that period.
Diagnosing the infection can be challenging. The use of clinical signs, patient history, and a series of diagnostic tests are all critical information needed to solve your pet’s condition. Commonly used diagnostic tests include Wood’s lamp examination, microscopic hair follicle examination, and laboratory culture of hair follicles.
Wood’s Lamp: This is a good first step, however it does have its limitations. In a positive animal the infected skin lesion will fluoresce very brightly under a Wood’s lamp. Only about 50% of Microsporum canis positive lesions will actually fluoresce.
Microscopic Examination: Viewing the hair follicles under a microscope can show signs of the infection. Once again, if positive this test is definitive, but not all positive dogs will show the infectious agents under microscopic exam.
Culture: If suspected, the only way to truly know if and which dermatophyte that your pet is infected with is by culturing the lesion. Samples of the lesions are typically sent to an outside laboratory for culture and can take days to receive the results. Repeat cultures may be performed as monitoring and/or as definitive testing for complete resolution of the infection.
Once your pet is diagnosed with ringworm, treatment is initiated as soon as possible. Oral antifungal medications are typically started on all cases, and some patients may even require topical treatments in addition to their systemic medications. Treatment protocols to fully resolve your pet’s infection often last months.
Like most infections, young and old pets, along with any immunocompromised pets, are much more susceptible to infection.
Due to the potential for transmitting the infection to other pets and humans within the household, thorough cleaning and sanitation is required. If at all possible your pet should be kept in an area that is easily disinfected and separate from other pets until full resolution of the infection is confirmed. Vacuum and sanitize on a regular basis, always allowing appropriate contact time for any household cleaner used to clean the area. If any lesions are found on you or your family contact your family physician immediately.
While it may be time consuming and difficult to treat, overall dermatophytosis has a great prognosis and is curable if treated appropriately. Please contact the VCMC if you have any additional questions.