Ringworm in pets

Ringworm is not a worm but a fungal infection of the skin, hair and claws. It is common in cats, less so in dogs, and also affects rabbits, guinea pigs and other small animals. It passes readily between animals and people, which makes prompt treatment and thorough cleaning important.

Cause and spread

The fungi responsible are called dermatophytes. One species, Microsporum canis, accounts for nearly all cases in cats and many in dogs; others are picked up from rodents, hedgehogs, cattle or soil. Infected hairs and skin scales carry microscopic spores, which spread by direct contact and on bedding, brushes, furniture and clothing. The spores can survive in a house for many months.

Kittens and puppies, long-haired cats, and animals that are old, ill or living in groups are most at risk. Some animals, especially long-haired cats, carry the fungus with no visible signs.

Signs

• Roughly circular patches of hair loss, most often on the head, ears and front legs.
• Broken, stubbly hairs, scaling and crusts.
• Reddened skin; itching varies and is often mild.
• Misshapen or brittle claws.

Many other skin conditions look similar, so the diagnosis needs confirming.

Diagnosis

A vet may examine the coat under an ultraviolet lamp, under which some infected hairs glow green, and look at plucked hairs under a microscope. Confirmation comes from a fungal culture, which can take two to three weeks, or a faster laboratory test for fungal DNA.

Treatment

A healthy animal will often clear the infection unaided over several months, but treatment shortens the illness and reduces spread. It normally combines:

• an antifungal medicine by mouth, given for several weeks;
• antifungal washes or rinses applied to the whole coat, usually twice a week.

The coat of a long-haired animal is sometimes clipped. Treatment continues until tests show the fungus has gone, commonly six weeks or longer, and stopping when the skin looks better leads to relapse. All the animals in the household are examined, and those in contact may be treated too.

Cleaning the home

• The infected animal is kept to one or two rooms that are easy to clean.
• Floors and furniture are vacuumed frequently and the dust disposed of outside.
• Bedding, blankets and soft toys are washed on a hot cycle, and items that cannot be cleaned are thrown away.
• Hard surfaces are washed with detergent and then treated with a disinfectant known to kill fungal spores, such as suitably diluted household bleach.
• Brushes, collars and carriers are disinfected or replaced.

Ringworm in people

In people ringworm shows as a red or darker, scaly, itchy patch, often ring-shaped with a clearer centre. Children, older people and anyone with a weakened immune system catch it most easily. Most cases on the body clear with an antifungal cream from a pharmacy; infection of the scalp, or a rash that does not improve, needs a doctor. Hands are washed after handling an infected animal, and disposable gloves and an apron are worn when applying its treatment.

Other feline conditions are described under common health problems in cats.