Ringworm View In Dogs

Condition Overview

Ringworm is a fungal infection that invades the hair and hair follicles. Ringworm gets its name from its appearance: a spreading circle of hair loss with scaly skin at the center and a red ring at the outer rim.

Symptoms

Typical areas of involvement are the face, ears, paws, and tail. A spreading circle of hair loss with scaly skin at the center and a red ring at the outer rim. Black fly bites in the groin area in the spring will also have this ringed appearance.

Atypical ringworm is common, with irregular areas of hair loss associated with scaling and crusting.

Ringworm itself is not an itchy skin condition, but secondary bacterial infection with scabs and crusts can provoke licking and scratching. Ringworm can invade the nails. This results in nails that are dry, cracked, brittle, and deformed.

A kerion is a round, raised, nodular lesion that results from a ringworm fungus in combination with a bacterial infection that invades the roots of the hair. In most cases the fungus is Microsporun gypseum and the bacteria is a type of Staphyllococcus. Kerions occur on the face and the limbs. Therapy involves treating the bacterial component.

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Causes

Most cases are caused by Microsporum canis. Ringworm in dogs is primarily a disease of puppies and young adults. Ringworm is transmitted by spores in the soil and by contact with the infected hair of dogs and cats, typically found on carpets, brushes, combs, toys and furniture.

Diagnosis

Ringworm mimics many other skin diseases, so an accurate diagnosis is essential. Hair infected by Microsporum canis may fluoresce green under an ultraviolet light ("Wood's light"), but false positive and false negative results are common, making this test somewhat unreliable. Ultraviolet light is used as a screening tool only.

Microscopic examination of hairs plucked from areas that fluoresce can sometimes provide an immediate diagnosis, but the most reliable method of diagnosing ringworm is by fungal culture. Some hairs are plucked from the abnormal area and placed in a special medium to grow out any fungus that is present. Results may take up to 2 weeks.

Treatment

Although mild cases resolve spontaneously in 3 - 4 months, all cases of ringworm should be treated to prevent progression and inhibit the spread to other pets and people in the household. Trimming the hair around the bald spots will help prevent the fungus from spreading and also make the area easier to treat. You may need to re-trim the area weekly until the infection has cleared.

With only one or two areas of involvement, apply a topical anti-fungal agent containing miconazole 2% cream or 1% lotion, an antiseptic soap containing povidone iodine (such as Betadine skin cleanser), or chlorhexidine (such as Nolvasan) twice daily in the direction of the lay of the hair. Continue treatment until the skin is healed. Be ready to treat the dog for at least 4 - 6 weeks. This will help prevent minor fungal problems from turning into a more serious bacterial infection.

When several sites are involved, repeat the treatment just described, and add an anti-fungal shampoo containing miconazole or another shampoo labeled for the treatment of ringworm. Allow the shampoo to sit for 15 minutes before rinsing well, to give it time to work. Continue to treat for 2 weeks beyond the apparent cure (disappearance of symptoms).

In difficult cases, your veterinarian may prescribe an anti-fungal drug called Griseofulvin. Ketoconazole, itraconazole, and other drugs of the imidazole group are also effective, but may not be approved by the FDA for treating ringworm in dogs. Griseofulvin, itraconazole, and ketoconazole have serious possible side effects and should not be given to pregnant females because they may cause birth defects. Anti-fungal drugs require close veterinary counseling and supervision.

Prevention

Ringworm spores can survive for up to 1 year and should be eliminated from the environment.

• Keep your pet well groomed. Regular brushing will help remove fungal spores before they can cause further infection
• Regular vacuuming will assist in controlling the fungus by removing any possible contagious hair from the floor.
• Discard the dog's bedding
• Sterilize grooming equipment in a 1:10 dilution of bleach
• Vacuum the carpets at least weekly to remove infected hair
• Mop and wash hard surfaces (floors, counter tops, dog runs) using diluted bleach
• Technical Captan can be used as a spray in a dilution of 1:200 in water to treat a kennel
• Keep the infected pet isolated from other dogs to prevent the spread of ringworm

Support

Please contact your veterinarian if you suspect your pet may be infected with this condition.