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“Ringworm” and what causes it?


“Ringworm” is the common name given to a fungal infection of the superficial layers of the skin, hair and nails. Ringworm infections can occur in humans and in all domesticated species of animals. The name comes from the classical appearance of the round, red, raised ‘ring’ marking the boundary of inflammatory lesions in people infected with the disease.{{more}} The common name of ringworm is somewhat misleading, in that it is not an infection caused by a worm, and the infected areas are not always ring-shaped. The fungi responsible for ringworm infections belong to a specialized group known as dermatophytes, so the medical name for this disease is dermatophytosis.

Ringworm fungi feed on the keratin that is found in the outer layers of the skin, hair and nails. In animals, the fungi commonly infect hair follicles, which causes the affected hair shafts to break off at the skin line. This usually results in round patches of hair loss. As the fungus multiplies, the lesions may become irregularly shaped and spread over the dog’s body.

What does ringworm look like?

In the dog, ringworm lesions usually appear as areas of hair loss (alopecia) that are roughly circular. As these circular lesions enlarge, the central area heals and hair may begin to re-grow in the middle of the lesion. The affected hair shafts are fragile and easily broken. These lesions are not usually itchy, but sometimes they become inflamed and develop a scabby covering. In most cases, there are several patches of alopecia scattered throughout the body. Occasionally, fungal infection of the nails may occur. The claws become rough, brittle and broken.

Some dogs may have ringworm fungi present in their hair or skin without showing any clinical signs of disease. These dogs can spread ringworm to other animals or people, despite having no obvious skin lesions, and are called “asymptomatic carriers.” Asymptomatic carriers are especially problematic in multi-animal environments such as animal shelters or kennels.

How is ringworm transmitted?

“Ringworm is contagious and can be passed between infected and non-infected individuals through direct contact or by contact with contaminated objects.”

Ringworm is contagious and transmission occurs by direct contact with the fungus. It may be passed by direct contact with an infected animal or person, or by handling contaminated objects or touching contaminated surfaces.

The fungal spores may remain dormant on combs, brushes, food bowls, furniture, bedding, carpet or other environmental surfaces for many months (reportedly up to 18 months). Spores may be killed with a solution of chlorine bleach and water (one pint of chlorine bleach (500 ml) in a gallon of water (4 liters), or a dilution of 1:10 to 1:100), where it is feasible to use it.

Contact with ringworm fungus does not always result in an infection. The amount of environmental contamination is an important factor in the development of a ringworm infection, as is the age of the exposed person or animal. Healthy adult humans usually are resistant to infection unless there is a break in the skin such as a scratch. Elderly people, young children, and adults with immune system weaknesses or skin sensitivities are especially susceptible to ringworm infection. If your child has ringworm, he or she may have acquired it from your pet or from another child at school. If you or your family members have suspicious skin lesions, check with your family physician immediately.

How long does it take to get it?

The incubation period between exposure to ringworm fungus and the development of ringworm lesions usually ranges from seven to fourteen days. Some cases may take up to 21 days before signs of infection develop.

How is ringworm treated?

Regardless of the severity of the case, treatment of ringworm in dogs is always necessary to avoid the spread of infection to children or other pets. The specific method of treatment recommended by your veterinarian to treat your dog will depend on the severity of the infection, how many pets are involved, if there are children or susceptible adults in the household, and how difficult it will be to disinfect your pet’s environment.

The most common way to treat ringworm in dogs is to use a combination of topical therapy (application of creams, ointments or shampoos) and systemic therapy (administration of anti-fungal drugs by mouth). In order for treatment to be successful, all environmental contamination must be eliminated.

Will my dog recover from ringworm?

The vast majority of dogs, if treated appropriately, will recover from a ringworm infection. Symptoms may recur if the treatment was discontinued too early or was not aggressive enough (i.e. only topical treatment was used), or if the pet has some underlying disease compromising the immune system. Occasionally, symptoms recur because the dog is a carrier of ringworm.

For further information, contact: Dr. Collin Boyle
Unique Animal Care Co. Ltd.
Tel: 456 4981