Ringworm in horses is a very contagious fungal infection of the horse’s skin that can spread rapidly from horse to horse. Ringworm is a zoonotic disease which means it can also spread from horse to human. Despite the name, ringworm is not always ring-shaped and has nothing to do with worms. The Trichophyton and Microsporum species of fungi that cause the disease flourish in wet British winter weather.  This fungus grows across the surface of the skin and around the hairs, producing a variety of changes affecting the horse’s coat and skin. 

What are the signs of ringworm in horses

Sometimes all that you notice in the early stages of the horse having ringworm is tufts of hair that can appear raised up from the rest of the coat , you may even notice a slight swelling underneath. Many horse owners expect ringworm patches to be circular, but while it can be, ringworm can be any shape and size.

The tufts of affected hair fall out, leaving the skin underneath looking raw and sore. Typically, ringworm develops into grey, flaking areas with broken hairs, but the coat will gradually reappear over the next month.

Ringworm can appear in many different ways. If your horse has a skin rash, sore or bald area for which there is no other obvious explanation, you should have the horse checked and treated for ringworm to reduce the risk of the infection spreading further.

Ringworm can appear anywhere on the horse’s body, but the most common sites are where the skin is in contact with the tack or harness, such as the saddle or girth areas. 

Any sores on the skin can give the ringworm an opportunity to invade the skin. Young horses are typically more at risk, probably because they have less immunity. Older horses usually have more mild signs of ringworm and recover more quickly.

How is it spread?

The infection spreads either by direct contact, or on tack, rugs, grooming kit or buckets. Also, the ringworm fungus will produce spores that can remain dormant on woodwork for more than a year, contaminating stables and fencing.

Horses with ringworm should not travel as they spread the condition, so training and competition schedules can be interrupted. If you notice ringworm then it is important to act quickly.

It is important to remember that also racehorses (and some other competition horses) with dermatitis (skin disease) that may be ringworm require a veterinary certificate that they are not contagious before racing.

Ringworm can also be found in dirt and wood. Ringworm spores can reach anywhere, and you won’t know it’s there until a horse develops the condition. The most common method of transmission is from one horse to another, followed by brushing against something made from wood. Ringworm spores are hardy and resistant to mother nature’s attempts to break them down. 

An infected horse can roll in the dirt or rub against a wooden structure or post and deposit the spores. Another horse then can come along and pick up the spores simply by rolling around in the now contaminated soil or rubbing up against the same spot that the infected horse touched. 

The spores lie dormant until they find a host to cling to and propagate. Once the spores find a host, they take hold of the base of the hair shaft where its favourite food, keratin, is the most abundant. Keratin, a hair protein, is a key component of every hair shaft.

How is ringworm diagnosed? 

If you suspect ringworm, it is important to speak to your veterinary surgeon who will guide you. Your vet may be able to diagnose the ringworm by looking at the skin lesions, if it is obvious. 

Often, laboratory tests are needed to be certain: samples are examined under the microscope for fungal spores. Sometimes, a culture of the fungus is required, which means it can take 10 days or more before the vet has an answer as the laboratory will culture the test.

Horses can catch ringworm from other animals, particularly cattle or dogs, but they can also pass it on to humans. It is one of the few conditions you can catch from your horse, so for that reason alone, the infection needs to be treated seriously.

If you notice your horse has even a mild skin irritation and you develop a rash, you should seek medical advice at once. Autumn, winter and early spring are the most common times for outbreaks of the infection.

What is the treatment for ringworm in horses?

The incubation period for ringworm is between one and four weeks. Once infected, lesions usually appear within 7 to 21 days depending largely on the immune status of the horse. If left, most cases will eventually clear up, but treatment is recommended.

The aim of treatment is to kill the fungus and second, to destroy the infective spores. It is important to cure the infected horse, but also vital to reduce the environmental contamination.

To treat the horse, there are a number of effective medical washes, shampoos and sprays that can be applied to the skin. Initially the whole horse should be treated, then any areas that show clear signs of infection as suggested by your vet.

You should wear disposable gloves  while treating the lesions and you should clean your hands with a suitable wash afterwards. 

If untreated on your horse, a case of ringworm in a single horse will typically resolve itself over a few months, leaving the horse with some level of immunity against future cases of the same type of ringworm, but not all fungal skin diseases. 

Any damaged skin will return to health and any missing hair will regrow with time, although sometimes a difference in hair colour may be apparent for some time.

Due to the highly contagious nature of the fungus, in both the host species and others, and its ability to contaminate the local environment, it is strongly recommended that you act quickly.

Tips if you have an outbreak of ringworm

If you think that your horse has ringworm, you should carry out the following control measures.

  • Keep any suspected horses with ringworm separate in their own stable. If an infected horse is isolated he should not spread the infection, provided he cannot touch other horses and care is taken in handling the potentially affected horse
  • Do not groom or clip an affected horse because of the risk of spreading spores
  • Wear protective clothing and disposable gloves when handling the affected horse
  • Avoid riding an affected horse. This reduces the chance of spreading the infection and prevents skin sores from being rubbed by the tack
  • Do not share rugs, tack or grooming kit – girths are a common item on which ringworm can spread
  • Treat your riding boots/half chaps/gaiters to avoid spreading to another horse
  • Ask your vet to check any suspected horse
  • Treat your horse, his stable, and if relevant the horse’s lorry or trailer

Can I prevent ringworm?

There are several things you can do to help prevent yourself or your horse (and other pets/animals) getting ringworm, including:

  • Good stable management
  • This is the key to both preventing ringworm and limiting its spread, because it is so easily passed between horses and people.
  • Cleanliness and hygiene
  • Disinfecting a new stable before your horse moves in is a wise precaution. You should also disinfect any stables and areas (such as fence posts) touched by a horse you know has had ringworm.
  • Isolate new horses and any horses that come into the stable environment, ideally two to three weeks.
  • Don’t share tack and equipment

If a horse is isolating, ensure their kit and things like mucking out tools are stored separately. As few people as possible should have contact with the horse until they get all clear.

Further reading

Ringworm in Horses (Dermatophytosis) – UC Davis

Dermatophytosis in Horses – Integumentary System – MSD Veterinary Manual

Dermatophytosis (ringworm) – Pilsworth – 2007 – Equine Veterinary Education – Wiley Online Library