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Ringworm in Horses (Dermatophytosis)

RINGWORM IN HORSES

 

 

What is ringworm?

Ringworm is a fungal infection of the skin and hair shafts.  It causes hairless, flaking or crusting lesions which may be itchy.  Occasionally raised non-itchy nodules may be seen.  The most common sites to see lesions are areas of skin prone to minor damage, such as in the girth area, on the face and under the saddle.  Secondary infection can cause discharge and pain.

 

Ringworm is commonly seen on the face

 

How do horses get ringworm?

Ringworm occurs when fungal spores enter the outer layers of skin through areas of minor damage.  The spores survive in the environment and can be transferred from walls, bedding, brushes, tack and occasionally from trailers, lorries and wash buckets.

 

 

Why is ringworm a problem?

Ringworm is a zoonosis – this means it can infect people as well as animals.  It is highly contagious and can spread quickly through a yard by direct and indirect contact between horses. 

 

Horses with active ringworm infection cannot compete at affiliated or Jockey Club events.  Infection can last up to 3 months if not treated.  The growing fungus produces highly resistant infective spores which can survive in the stable environment for up to 20 years to cause repeated outbreaks of ringworm.  Treatment reduces the shedding of spores and so reduces the infective load in the stable environment.

 

 

Diagnosis

Lesions caused by ringworm can be very variable in appearance.  To confirm whether or not ringworm is present, samples of hair can be taken for examination under a microscope and for fungal culture.  Skin scrapings can also be used from areas that have already lost all the hair.

 

Treatment 

We recommend using a licensed, concentrated anti-fungal solution that kills the fungus and its spores.  The concentrate must be diluted before use, following the manufacturer’s instructions exactly; too weak a solution will be ineffective – too strong a solution can burn the skin.

 

Clipping affected horses before treatment greatly improves contact between the solution and the affected skin.  At the first treatment, the solution should be applied to the whole horse; subsequently only affected areas of skin need to be treated.  The solution should be applied at least four times as instructed, making up a fresh batch of solution each time.  Where there are a lot of scabs, these should be gently removed without causing further damage to the skin.

 

An anti-fungal disinfectant should also be used to thoroughly disinfect brushes, tack and rugs to prevent spreading the infection to other horses and to avoid re-infecting a horse that has already recovered from its ringworm infection.  Virkon and Trigene are both suitable.

 

Horses affected with ringworm should be quarantined from other horses and separate equipment used for their care and management.  Anyone handling a horse with ringworm should wear gloves and take care to avoid skin contact to avoid becoming infected themselves.

 

The incubation period after exposure to ringworm is 2-3 weeks – so by the time lesions are seen on one horse, others may already be infected too.

 

 

Environmental Cleaning

All the skin debris and clippings from infected horses should be collected up and burnt to avoid further contaminating the environment.  Thorough cleaning and disinfection of stables, trailers and lorries will help reduce the number of infective spores to which horses are exposed.  Good hygiene should be practiced in all yards whether or not there is or has been an outbreak of ringworm!