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Background:
Despite its name, ringworm infection is not caused by a worm but by a
fungus. Similar to athlete’s foot in humans, the fungus causes a superficial
infection of the skin and hair follicles. Three types of fungus are usually
responsible for these infections: Microsporum canis, Microsporum gypseum and
Trichophyton mentagrophytes.
Ringworm is generally a
disease of younger animals. The fungus is transmitted by spores which live
in soil or may be transmitted between pets on brushes, toys and bedding.
Humans can also contract an infection if they come into contact with an
infected pet. Children and elderly people are especially at risk.
Clinical Signs:
In humans, ringworm infections typically appear as circular, red raised
lesions on the skin, hence the name. However, in cats and dogs, the
infection does not always appear as a ring on the skin. In pets, ringworm
infection may cause patchy hairlessness in a single area or in several areas
of the body. Dogs are most commonly affection on the nose, ears, face and
paws. Cats also are affected on the head, but often have spores or hairless
patches on their limbs as well. These spots are rarely itchy, but a
secondary bacterial infection may cause the lesions to scab, bleed or itch.
Diagnosis:
Ringworm is diagnosed by veterinarian with a few simple tests. The spores of
the fungus will glow green under ultraviolet light, although occasionally
this may not be seen. A fungal culture may be grown from a sample of the
hair surrounding the lesions. Fungal cultures take awhile to grow and
develop, so your veterinarian may prescribe medications in the interim. Hair
follicles can also be microscopically examined in the hopes of identifying
spores.
Treatment:
Treatment of ringworm infections varies depending on the spread of
infection. If the infection is very local to one spot, the area may be
shaved and cleaned using special shampoos. A topical anti-fungal medication,
such as 2% miconazole, may be applied to the lesion regularly by the owner.
In more generalized cases of ringworm, your veterinarian may recommend not
only clipping the hair and using topical therapy, but also a prescription
oral medication called Griseofulvin (Fulvicin).
Treatment of
ringworm requires great care by owners. Gloves should always be worn when
handling infected animals. Bedding should be discarded and grooming tools
should also be sterilized with a 1:10 bleach solution. Ideally, pets should
be isolated to prevent spreading spores onto carpets and furniture. If this
is impossible, carpets and furniture should be frequently vacuumed to pick
up spores and hair.
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