Ringworm

Ringworm

What is ringworm, and what causes it?
Ringworm is a fungal infection of the skin. Because the lesions are often circular, it was once thought to be caused by a worm curling up in the tissue. However, the condition has nothing to do with a worm.

There are several fungal species that can cause ringworm in dogs. These may also affect humans. The fungi live in hair follicles and cause the 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. The incubation period is 10-12 days. This means that following exposure to the fungus, about 10-12 days will pass before any lesions occur.

How is ringworm diagnosed?

Identification of the typical "ringworm" lesions on the skin
Fluorescence of infected hairs under a special light (however, not all the species of fungi fluoresce)
Culture of the fungus from affected hairs. This is method is the most accurate, but results take up to 2-3 weeks.

How is it transmitted?
Transmission occurs by direct contact between infected and non-infected individuals. It may be passed from dogs to cats and visa versa. It may also be passed from dogs or cats to people. If your child has ringworm, it may have been contracted from your pet or from another child at school. Adult humans usually are resistant to infection unless there is a break in the skin (a scratch, etc.), but children are quite susceptible. If you or your family members have suspicious skin lesions, check with your family doctor.

Transmission may also occur from the infected environment, so-called fomite transmission. This is often the method of transmission between animals in a household when brushes and combs are shared. The fungal spores may be killed using a dilution of chlorine bleach and water.

How is it treated?
There are several methods of treatment. The specific methods chosen will depend on the severity of the infection, how many pets are involved, if there are children in the household, and how difficult it will be to disinfect your pets' environment.

1. Griseofulvin This is an antifungal drug that concentrates deep in the hair follicles where it can reach the site of active fungal growth. Dogs with active lesions should be treated for a minimum of 30 days. Regular check-ups will be required to monitor progress of treatment. Griseofulvin is absorbed into the body much better if the tablet is given in a fatty meal. This can be accomplished by mixing a little cooking oil with the food.

2. Topical antifungal medication Your dog may be prescribed a cream to be applied directly on to the affected areas of skin. This also reduces the infectivity of the skin flakes, thereby minimising the risk of other animals or humans becoming infected from a contaminated environment.

3. Antifungal shampoo baths

5. Shaving of the affected areas This will remove the infected hair. This is invariably undertaken in full coated animals to accelerate the recovery period.

What should I expect from treatment?
Treatment will not produce immediate results. The areas of hair loss will get larger before they begin to get smaller. Within 1-2 weeks, the hair loss should stop, there should be no new areas of hair loss, and the crusty appearance of the skin should subside and the skin look more normal. We will in any case wish to monitor progress. After at least two weeks, your dog should be checked again.

How long will my dog be contagious?
Infected pets remain contagious for about 3 weeks if aggressive treatment is used. Contagion will last longer if only minimal measures are taken or if instructions regarding treatment are not diligently followed. Minimising exposure to other dogs or cats and to your family members is recommended during this period.

I have heard that some dogs are never cured. Is this true?
When treatment is completed, ringworm should be cured. Although a carrier state can exist, this usually occurs because treatment is not long enough or aggressive enough or because there is some underlying disease compromising the immune system.