Ringworm or dermatophytosis is not a worm but a fungus that can infect skin, hair, and nails; it can affect both animals and people. It appears in dogs and cats as areas of hair loss with or without a red ring in the center. Generally the lesions occur on the head, ears, or front legs; but can be anywhere on the body. It is also possible for a pet to be a carrier for ringworm, meaning they do not show any symptoms but are still shedding spores and can spread illness to others. This is most common in longhaired exotic cats. Animals contract ringworm via contact with other infected animals, carrier animals, or from the environment. The spores are very tough, and can survive on surfaces for a year. Young, geriatric, and immuno-compromised pets are the most susceptible. There are several species of dermatopytes; but Microsporum canis is the most common to infect dogs and cats. Generally patients that are infected are not itchy; and the incubation time from contact to symptoms is 10-12 days.
Dermatophytosis is diagnosed based on clinical signs, signalment, and testing. A Wood's lamp is a fluorescent light that can shine green on skin surfaces when ringworm is present. It has a low percentage of accuracy both with false positives and false negatives so other methods such as a fungal culture or cytology are more heavily relied upon. Occasionally it is diagnosed on a biopsy. Response to treatment is also important.
Therapy involves a multitude of strategies depending upon the severity of symptoms, health of the patient, and the number of animals in the environment. Medicated baths or mousses are frequently used to help kill ringworm. All pets in the household should be bathed to prevent the spreading of spores, even if they are not symptomatic. At one time dips were commonly used; but they are not present to use and can be harmful. Shaving, especially in longhaired cats can help to better treat the base of the hair follicles and allow for a quicker resolution. Topical antifungal creams may be recommended as well. Oral antifungals can be used; but there can be liver concerns with this treatment so it is utilized judiciously. Treatment generally is needed for at least 4-6 weeks, and should continue for at least 2 weeks past the resolution of symptoms. Longhaired exotic cats should continue to be bathed in antifungal shampoo since they are considered to be in a continual carrier state.
Other home care items include confining the dogs or cats and not letting them on the furniture or the human's beds to prevent the shedding of spores. Pet bedding should be washed with detergent and hot water at least weekly. Surfaces can be cleaned with a 10% bleach solution. Frequent vacuuming helps to remove infected hair and skin. Steam cleaning of the carpets is also beneficial. People with symptoms should refer to their doctors.
Although ringworm can be self-limiting, meaning it can resolve on its own, it can take several months for this to occur. It can be a very challenging disease to manage depending on the number of animals in the home, as well as their level of health. Your veterinarian plays an important roll in controlling this illness. It is best to bring your companions in at the first sign of a problem, and confine them right away.