It’s wonderful sharing your life with a pet, but not so good when the pet shares diseases with you. Ringworm is the ‘social butterfly’ of pet diseases and is quite happy to flit from pet to pet and from pet to owner. It can even spread from an infected owner to his or her innocent pet!
Is Ringworm a worm?
The term ringworm is a misnomer. It has nothing to do with worms. It is a fungus, or more correctly, one of several fungi that can affect animals and humans. Because of its tendency to expand outwards, it was believed to be caused by a worm that was progressively growing under the skin.
Ringworm disease has an interesting history. In the 1800s barbers, schoolchildren, and theatre seats were the main way the fungus spread. Because it was found that people recovered better without their hair, hair was plucked strand by strand or pitch plaster was applied and the hair was torn out. In the 1900s, London children with ringworm were sent to separate schools that offered the two ‘E’s’ – education and X-ray epilation therapy. Their hair fell out, but many children and workers also died from radiation-associated injury.
Today, many children, adults and pet owners get ringworm through direct or indirect contact with the infected hairs or skin of pets. Thankfully, nowadays the disease is fairly easy to treat without radiation, although some pet owners still pull their own hair out, but more in frustration!
Ringworm is caused by a group of fungi. The most common, causing about 70% of infections, is a contemptible bug known in the underworld as Micosporum canis. Another two equally villainous fungi can also cause ringworm.
Ringworm is easily transmitted to humans. About 50% of people living with a ringworm-infected cat will develop the infection. Children and young animals are most susceptible to infections.
What does Ringworm infection look like in a pet?
Ringworm in animals usually appears as a rapidly growing circular patch of broken hair. A ‘cigarette ash’ dandruff appears on the lesion and sometimes the patch has an inflamed margin. The hair may start to grow back in the centre of the patch while the extremity of the patch is still expanding. The infection is more common in young animals. In kittens, the patches usually occur on the head and feet.
However, in cats, ringworm may not cause any obvious effects and therefore can be quite difficult to detect, especially if the cat is long-haired. In other cases, the cat can become almost totally denuded. The ringworm fungus can also attack the claws of cats in which case the claws become roughened and pitted.
How is a Ringworm infection diagnosed?
Initially, your veterinarian is likely to scan the lesions with an ultraviolet lamp called a Wood’s light. In about 60% of cases, the infected hair shafts will glow a bright green colour. Sometimes the hairs in the lesion will be plucked and added to a culture medium where the fungus will grow. Alternatively, skin scrapings are taken and are then examined under a microscope after special staining.
Treatment of a Ringworm infection
Ringworm infections are treated in a variety of ways. Sometimes a cream, wash or medicated shampoo may be enough but usually a combination of several therapies is wise.
Antifungal creams are readily available and may be efficient for small lesions. With local lesions it is important that the area is clipped to remove infected hair. Be careful while you are doing this so as not to damage the pet’s skin. Burn any hair removed, as this will be contaminated with fungus. Also wear gloves to stop yourself being infected and be sure to thoroughly disinfect your clippers. Smear the cream over the area surrounding the lesion and over the lesion itself. The cream may have to be used for several weeks but if no improvement in seen in two weeks, please see your veterinarian.
In more complicated cases, oral antifungal tablets may be needed. Such medications are prescription products and are available from your veterinarian. These tablets may need to be used for three to four months to get rid of the infection.
Disinfecting the environment the animal lives in is important. The fungal spores will live on hair in the environment for over a year so sanitising the environment is vital or a recurrence is likely.
Destroy all bedding, blankets, brushes, combs, scratching poles and anything else that isn’t essential. Vacuum the house thoroughly and discard not only the contents but also the vacuum bag, as this will contain many fungal spores.
All remaining items should be soaked for an hour in hot water to which Betadine or iodophor has been added. The items should then be rinsed with a solution of one part chlorine bleach to ten parts water and air-dried in sunlight. You should have your drapes dry-cleaned and your carpets steam cleaned. Floors and walls should be cleaned with chlorine bleach if possible.
Ringworm can really be a tenacious infection. If you are having ongoing problems with ringworm infections in your pets, consult your veterinarian for details.
Dr Cam Day BVSc BSc MACVSc is a veterinary surgeon and animal behaviour consultant.
By Dr Cam Day BVSc BSc MACVSc
Last updated on 16 December 2020