Scabies and Ringworm in Dogs and Cats: How to Spot, Treat and Prevent Them

Itchy dog scratching
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Sarcoptic mange is an intensely itchy disease caused by an infestation of mites.

Skin diseases are common problems in dogs and cats. Many of these diseases are not contagious, but some can be transmitted to other pets or people. Two common contagious and easily transmissible skin diseases are dermatophytosis (ringworm) and sarcoptic mange (scabies). Understanding what causes these diseases and how they are transmitted and treated is key in minimizing the potential for zoonotic transmission.

Ringworm

Caused by a fungal organism, dermatophytosis, or ringworm, is an infection of the hair shafts and upper layer of skin. Although there are thousands of fungi in the world and approximately 30 species classified as dermatophytes, relatively few cause skin diseases. Of those that do, the infections are caused by contact with another infected animal or exposure to infective material (spores) in the environment. These spores may be found on bedding or grooming tools used on an infected animal and on any surface with which the infected animal came in contact. The spores may also be present in the environment; certain ringworm infections may be caused by fungal organisms found in soil.

Any dog or cat can develop a ringworm infection but it is most commonly diagnosed in young kittens or puppies, in animals with immunosuppressive diseases (such as cancer or other illnesses) and in animals under stress or living in high concentrations (e.g., shelters). Also, having long hair seems to be a predisposing factor in cats.

Dermatophytosis can have a highly variable appearance in animals. It can cause a single skin lesion or many lesions, or it may affect most of the pet’s skin. Some pets with dermatophytosis are itchy, while others are not. Dermatophytes infect hairs and superficial layers of the skin and nails, resulting in patches of hair loss, round or irregularly shaped skin lesions and crusty scales with irregular edges. Hairs may be broken or break easily when the pet is touched, and the skin may be red. Lesions may appear anywhere on an infected animal.

Some animals may be asymptomatic carriers, meaning that they show no signs but can still infect others and shed spores into the environment.

In people, a ringworm lesion starts as a single, red, round, mostly flat lesion with a scaly or crusty appearance. Zoonotic lesions in people typically appear on areas that come in contact with the pet, such as the abdomen, arms or face. Children are especially susceptible. Infected people may or may not itch.

Diagnosis is based on history, clinical signs and a fungal culture. Dermatophytosis is treatable and curable. Treatment for animals usually requires topical and systemic therapy. Topical therapy (rinses and soaks) helps speed resolution and minimizes the spread of spores into the environment. The disease can self-cure, but treatment is recommended to minimize its spread. Treatment can take anywhere from a few weeks to several months. Spread of dermatophytes can be minimized through routine cleaning of the home and keeping the animal isolated in a room that can be easily treated.

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