Worms ain't worms - How to beat ringworm

Dr Peter Higgins explains Ringworm, and the importance of treating the fungal infection before it spreads.

"Not all worms were created equal", explains Dr Peter Higgins, "especially not that confusingly-named fungal infection, Ringworm."

"Do you remember the “Oils ain’t oils, Sol” television advertisement? Well, the same can be said about worms. Ringworm, particularly, ain’t worms! A worm does not cause it at all. In fact, ringworm is caused by a fungus."

What is Ringworm?

The medical name for Ringworm is Dermatophytosis. It is a common infectious disease involving the superficial layers of the skin, hair and claws. Keratin (a protein that builds skin and hair) provides the primary nutritional source for dermatophytes, or fungi.

Microsporum and Trichophyton are the groups of fungi that are most often associated with animal infections and, in dogs, approximately 98 percent of infections are attributed to the species Microsporum canis.

Who can get it?

Any species of animal can acquire Ringworm, but some species are more susceptible than others. Dogs are one of those species, and dogs in high-risk categories can acquire Ringworm very easily.

  • Dog populations at risk of developing infection include:
  • Puppies 
  • Dogs with immunosuppressive diseases 
  • Dogs being administered anti-inflammatory or immunosuppressive drugs, such as corticosteroids
  • Dogs with genetic susceptibility
  • Dogs infested with ectoparasites, such as fleas or mites
  • Dogs in large dog populations like animal shelters, pet stores, large kennels or multiple dog households, or which attend dog shows.

What does it look like?

The classic lesion begins as one or more pinkish, scaly pieces of skin, and spreads around the body. As the fungus invades the hair follicle, the hair becomes brittle and breaks off close to the skin. The mature lesion is well defined; it is round, discrete, and covered with a scaly, greyish ‘skin‘.

Variations from the above, however, are quite common; sometimes it looks like small scaly patches. The patches on the skin often give the impression of the hair having been shaved. Lesions can occur on any part of the body, but they are commonly found on the head, ears, tail and front paws.

The broader animal health problem is that many dogs carry fungal particles without showing any sign of disease. In other words, they are carriers of the disease and can infect other animals.


There are five different methods of diagnosis.

  • Observation of the dog
  • Thorough physical examination of the skin and hair
  • The use of an ultraviolet light called a Woods Lamp, which causes the affected hair to glow a greenish-blue colour. This is due to the presence of a fluorescent agent found in the fungus on the hair.
  • Fungal particles can be detected by the hairbrush technique. This is simply a matter of placing the dog on white paper and brushing it thoroughly with a fine hairbrush. The particles will be seen on the white paper after you have finished brushing.
  • Skin and hair scrapings can be taken and examined under a microscope to identify the dermatophyte fungus.


The treatment for Ringworm may need to be given for weeks and sometimes months. Skin creams very rarely work; at best, they stop the spread of the existing lesions around the body.

A drug called Griseofulvin is generally an effective treatment, It is a prescription medication, available in tablets, suspension and capsules. Other drugs are also available, but Griseofulvin is the most common and is very cheap.

In my experience, if this sort of tablet is not given, all the creams in the world will not successfully treat the Ringworm infection.

Why treat it?

While Ringworm is not life threatening, it is a highly contagious disease that can spread very quickly among all sorts of animals. It can cause permanent skin lesions and impair the immune system, making the dog (or cat, or person) more susceptible to other diseases.

Treatment of individual dogs can take weeks or even months to be fully effective. This is also the case for other animals.

We need to treat this disease seriously because it can affect the health and wellbeing of our dogs and, for this reason alone, we should be continually vigilant.

Further to this, as a recognised group of dog experts we need to lead the way on responsible pet ownership in our communities.

How can I stop it?

Fungi love to live in warm, damp environments. In fact, the fungi that cause Ringworm commonly live in the soil, where they process the hairs and skin cells shed by animals and humans during the natural and continuous cycle of skin and coat shedding.

The prevention of Ringworm cannot be left to one action. Several things must be done at the same time. It is not really that hard to do this, but it is time-consuming. We must treat the environment first, as well as the dog itself.

This means that kennels must be fully disinfected regularly and continually monitored for any likelihood of this organism. If kennels do find a Ringworm infection, it does not mean that those kennels are unclean or not well managed.

Even the cleanest of kennels can acquire fungal spores because it is so easy to do so – any kennels that are cleaning up Ringworm should be commended. In any case, all kennels should have preventative measures in place so that Ringworm does not occur.

There are three basic steps that can help prevent Ringworm.

  • Regular cleaning. Remove and clean blankets and other bedding from the dog’s quarters so that Ringworm fungus cannot grow and multiply.
  • Mechanical removal of skin cells and hair. Vacuuming areas where animals have been, followed by disinfection, will help to control the spread of ringworm infections. 
  • Disinfection. It is commonly believed that fungal spores are highly resistant to disinfectants but this is not true. Dermatophyte spores are susceptible to several common disinfectants such as benzalkonium chloride, diluted (1:10) chlorine bleach, or strong detergents. Chlorhexidine has not been found to be effective as an environmental decontaminant.

And what about Dog Shows?

Dogs with existing Ringworm infections can very easily infect other dogs at shows. The time that a show takes to be completed is certainly enough time to spread spores or, for that matter, dermatophytes themselves.

In other words, the probability that many previously healthy dogs could acquire Ringworm if one infected dog is at a show is very high. We therefore need to take a very strict and firm approach to dogs with Ringworm.

In my opinion, as strict as it may seem, a dog with Ringworm should not be allowed at shows for a quarantine period of six weeks. At the end of the six-week period, a veterinarian should supply a health certificate before the dog can be shown again.

In other words, the infected dog could not automatically be shown after six weeks, but rather the owners would need to demonstrate that the Ringworm had been treated and all dogs from the same location had undergone appropriate preventative and treatment regimes as certified by the consultant veterinarian. If the same dog again has Ringworm within a two-month period of re-entering shows, the next quarantine period should be 12 weeks.

Why so strict?

We all know that dogs are a delight to own, and we are indeed privileged to experience their company. Dogs give their owners unqualified love and approval in boundless measure. It is therefore our responsibility to ensure that our own dogs remain in peak condition, as well as the entire canine population.

Ringworm is not a life-threatening disease, but it is one of the most infectious. We all want healthy dogs, so let’s control infections.

Did you know?

Ringworm is not only infectious between dogs, it is sometimes zoonotic. This means that it can be transmitted between animals of different species – and humans can catch it from an infected dog.