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    Posted on by Abii Dowdy

    What is ringworm?

    Ringworm, otherwise known as dermatophytosis, is a fungal skin infection caused by a dermatophyte fungus. The fungus infects dead tissue in the superficial layers of the skin, spreading quickly. The spores of the fungus eat away at the hair, causing the slowly widening bald patches that are typical of the skin disease.

    The skin lesions usually start as small raised spots from which the hair is lost. The bald patches then become scurfy or a thick dry crumbly scab may form. However, ringworm can  present in many different ways so often our vets will recommend testing to rule the condition in or out.

    In many cases there may only be a couple of lesions but if left untreated and especially if spread by grooming, the condition can become extensive, covering a large portion of the horse. The infection is highly contagious and whole groups of horses can become affected in an outbreak; young and immunocompromised horses are particularly susceptible to infection. Ringworm is also a zoonosis, meaning that people can also contract the infection and develop skin lesions.

    There is a long period (up to 3 weeks) where a horse may be infective, without any clinical signs being obvious; this makes ringworm very good at spreading through a yard before it is noticed. Spores can be spread by direct contact between horses, on tack, grooming equipment and clothing etc. The spores are very resistant to destruction and can survive for many years, especially in wooden fencing and stables.

    How is it diagnosed?

    The skin lesions are usually (but not always) characteristic and may look similar to other skin conditions such as rainscald or folliculitis. Often if the lesion is highly suspicious of ringworm, our vets may suggest trial treatment.

    A sample of hair from the lesions can be obtained and the fungus then grown in the laboratory. Unfortunately, this can take 2-3 weeks and in many cases the horse has been successfully treated before the results of the culture are known. A new test looking for the fungus DNA in samples has been developed and can now give results in just 2 days.

    How is ringworm treated?

    If left untreated, some ringworm cases ‘self cure’ in 6-15 weeks, but treatment is highly recommended to reduce the risk of the infection spreading. Horses with ringworm are also prohibited from competing or racing.

    The most effective treatment is repeated topical application of enilconazole (Imaverol) designed to soak into the skin and hair shafts to deactivate spores. The solution can also be used to wipe over tack, boots, grooming kits etc to help limit the spread of spores.  Imaverol should be applied 4 times, at 3 day intervals, using a spray or sponge. Scabs should be removed prior to application to allow the solution good contact with fungal spores. At the end of a course of treatment, the lesions should have stopped spreading, no new lesions should appear and the skin should look healthy; new hair growth occurs relatively quickly.

    Horses are considered non-contagious on day 11, with treatment starting at day 1. After this time, even if bald patches remain, the horse should no longer pose a risk to others and is allowed to compete/race.

    In severe, generalised cases or where there is an outbreak in a group of horses, treatment with oral powders (griseofulvin) given in the feed for 10-14 days can be used.  These take up to six weeks to be effective and should be used in conjunction with topical (skin surface) treatments as described above.

    Following infection, horses usually develop an effective and long-standing immunity to further infection.

    Prevention and control

    If you suspect ringworm, contact your vet and ensure that the affected horse is treated as soon as possible. The horse should have its own grooming kit and tack, which should not be used on any other horse. Handlers should use gloves when dealing with affected horses and, where possible, these should be dealt with last. If possible, clipping should be avoided until the infection has resolved. Ensure the grooming kit, rugs and tack are thoroughly disinfected during and after treatment, using a product such as VirkonTM; the stable and fencing should also be disinfected after treatment.

    Can I catch ringworm from my horse?

    It is possible (but uncommon) for people to catch ringworm from horses.  The lesions are usually itchy and red patches or ‘rings’ may form and can occur anywhere on the body.  Your doctor should be consulted to confirm the diagnosis and for a suitable treatment.