Ringworm - signs, diagnosis and treatment

Despite the name, ringworm is not a worm (or even caused by a worm), but a fungal infection of the top layers of the skin and hair. The kinds of fungi that cause ringworm are called dermatophytes, and the most common one in pets is called Microsporum canis. While generally harmless, ringworm is highly contagious to humans, especially to children, the elderly and anyone with a compromised immune system (eg. people undergoing chemotherapy). As such, if you suspect you or your pet has ringworm it’s important to seek medical or veterinary treatment immediately.

How can humans and pets catch ringworm?

Ringworm can be caught from a variety of sources ranging from the soil, other people and also from your pets. It is one of the few infections that can be transferred from animals to humans. As the fungi can live on stray hair follicles and skin cells, it is quite easily transmitted. One species of ringworm (Microsporum gypseum) is a soil organism and can be picked up spending time in the garden. If you know your pet or another person has ringworm, avoid the following:

  • Skin-to-skin contact with an infected person or animal
  • Sharing of towels, clothing or sports gear
  • Contact with infected household items, such as a brush, pet clothing, towels and furniture.

Signs and Symptoms of Ringworm in humans

In humans, ringworm is commonly identified as a red and itchy skin lesion in the shape of a ring. If you suspect you have a ringworm lesion, please contact your healthcare professional for advice on treatment.

Signs of Ringworm in Dogs and Cats

While the telltale lesions that appear on humans also appear on cats and dogs, due to their fur coats it can be difficult to see them. In mild cases of ringworm, you may not notice anything at all. In more serious cases, you might notice the following symptoms:

  • Dandruff-like scaling in the depths of the coat
  • Red lesions on the head, chest, forelegs and the ridge of the back
  • Scaling, crusting, thickening and reddening of the skin
  • Circular patches of hair loss (alopecia) on the head, tail or the ridge of the dog or cat’s back

Diagnosis of ringworm in pets

If you suspect your pet has ringworm, it’s important to go straight to your vet, as diagnosis often requires a thorough clinical examination and testing. Your vet will use a combination of the following diagnostic tests:

  • Observation. Your vet will first examine your pet for any of the skin lesions and scaling that typically occur with ringworm.
  • Wood’s Lamp. This special ultraviolet lamp is designed to show up a yellow-green fluorescence. The fluorescent material is not actually the fungi themselves, but an excretion that sticks to the hair shaft. While this quick and non-invasive test will help diagnose some cases, it only picks up a percentage of Microsporum canis infections so a negative result does not rule out a ringworm infection.
  • Microscope. Your vet may gently pluck a small sample of hair surrounding the lesion and view the hair shafts under the microscope. This may allow the visualisation of fungal spores attached to the hair shafts.
  • Fungal culture. If your vet needs to confirm the diagnosis, they may send a hair sample to a lab for testing. While it can take up to four weeks for a conclusive diagnosis from the lab, early signs of the infection can be detected within a few days. A fungal culture can be necessary if results of other tests are inconclusive or if the particular species of ringworm needs to be identified.

Your vet may also perform additional testing to rule out other causes of the hair loss and skin lesions (eg. allergic skin disease, sarcoptes or demodex mites).

Treatment of ringworm

There are a number of options to effectively treat ringworm, depending on the severity of the lesions.

Creams and ointments

For mild cases, antifungal creams and ointments can be applied directly to the affected areas of your pet’s skin. If the infection is widespread, your vet may prescribe an antifungal shampoo to treat your pet’s entire body. It’s important that you only use ointments and shampoos that have been recommended by your vet, as other products may aggravate the condition.

Oral medication 

While ointments can be effective in mild cases, most of the time your pet will also need to take an oral anti-fungal drug to eradicate the infection. Treatment usually needs to be continued for at least six weeks and sometimes longer. When administering oral medication, remember the following:

  • Do not abruptly stop treatment, or stop it sooner than recommended, as the infection may recur
  • If you have other pets in the house, keep the infected animal separated
  • In some cases, it may be best to treat all animals together – your vet will be able to provide a recommendation on this.

Cleaning the house and furniture

As ringworm lives on both skin and hair, it can be easily transmitted by loose hair on carpet or furniture. At the same time as treating your animal for ringworm, it is recommended that you do a thorough clean of your home environment to remove any contaminated hairs.

  • Vacuum any carpet or furniture that your pet has contact with (including underneath beds and couches)
  • Wash down surfaces with a good cleaning agent
  • Restrict your pet to areas of the house that are easy to clean, such as rooms with tiles or floorboards.

It can take up to six weeks for treatment to be effective. During this time, your pet may still be contagious, so it’s important that members of the family (particularly children, the elderly or anyone with a compromised immune system) have minimal contact with the animal.

Prevention of ringworm

The fungi that cause ringworm love to live in warm, damp environments like soil. They then attach to hair and skin cells shed by humans and animals. While there is not much you can do to prevent these conditions, there are a number of other actions that you can take to prevent you and your family from catching the infection:

  • Regularly clean pet blankets and other bedding from your cat or dog’s quarters
  • Regularly dispose of any hairs from your pet’s grooming brush
  • Remove skin cells and hair from your home by regularly vacuuming the house
  • Disinfect other common areas of the house where your pets tend to live
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Illness and injury
Pet safety - common problems and dangers
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highly contagious
ringworm
worm
worming
deworming
ring
deworm