What is ringworm? The name of this disease is misleading. Ringworm is not caused by a worm, nor does it often form a ring, except sometimes in humans. It is a skin disease cause by a fungus that grows in the hair follicles. There are a variety of species of fungus involved in causing ringworm, but the main variety in dogs and cats is Microsporum canis. Tricophyton metagrophytes is another seen in disease, but more often in farm animals than pets. What animals can be infected with ringworm?
The ringworm fungus seems to be able to infect the skin of any mammalian species, including humans. Cats are affected more frequently than dogs. It is likely that rodents act as a source of the disease, and cats have greater contact with these. What disease does ringworm cause?
The fungus of ringworm infects the hair follicles, causing the hair to fall out and irritation of the skin resulting in scaling, sores and/or scabbing. This fungus affects small areas, usually about the size of a 10p piece or so, most frequently around the head and neck. Although the disease is unsightly and irritating, it is not serious. The disease is frequently self limiting, eventually going away by itself over a course of a few weeks in many cases. In cats, however, the fungus M. canis is able to form a carrier state – although the skin sores disappear with time, some cats still carry the fungus and are still infectious. What can be done to diagnose ringworm?
At least half of the type of fungus that causes the problem in dogs and cats will fluoresce under an ultraviolet lamp, which makes a very quick test for the disease. However, not all cases will show up this way so other methods can have to be used. Examination of hairs plucked from the affected areas under a microscope may see the fungus growing there. The only certain method is to try to grow the fungus in a culture dish from plucked hair or hair brushings, but it can take up to 2 weeks for the fungus to grow to know the results. What is the treatment for ringworm?
Treatment can be given in the form of tablets or by using anti-fungal preparations on the skin. The most effective treatment is to use both methods at the same time. The tablets contain a drug called griseofulvin. This drug can cause deformities in an unborn foetus, so should not be given to pregnant animals and precautions should be taken by women of child-bearing age when handling this drug. It is otherwise quite safe. It usually need to be given for at least 3 weeks to cure ringworm. The washes available for the skin include Imaverol wash and more recently Malaseb shampoo – the latter is probably the more pleasant to use. Bathing is usually required weekly while treatment if going on. For single ringworm lesions, it is possible to use human athelete’s foot remedies such as Daktarin cream. These are what humans should use who become infected from their pets.