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Sweet Itch

Technically called culicoides hypersensitivity sweet itch refers to a skin condition caused by an allergy to midge saliva.

Symptoms

Itching which can be all over the body but is mainly centred on the mane and tail and is seasonal with the horse mainly affected over the summer grazing season from March-October. Often the mane and tail hairs are broken, and the underlying skin is thickened and can become ridged in appearance. The itching can be severe with horses taking every opportunity to rub on fence posts or stable door frames that they can. The skin can become broken with the development of open sores, and it can be a debilitating condition.

Diagnosis

A diagnosis can be made from clinical examination and history taking in a lot of cases due to the classic appearance and pattern of disease. The diagnosis can be confirmed via intradermal skin testing.

Treatment

The mainstay of treatment is management. The itch is caused by an allergy to midge saliva so if we can prevent the midge from biting the horse we can prevent the allergic reaction in the first place. Management strategies include:

• Physical covering – an affected horse must be covered in insect proof material all over 24 hours a day during the whole midge season – generally from March to October but assess each year on its own. This can be achieved using a fly rug with neck, belly and tail covers, ‘bug rugs’ or sweet itch rugs as well as a full face fly mask with ear covers. It can be overwhelming to commit to but it really is the key, on a rainy day either use a waterproof fly rug or a rain sheet over the top of the fly sheet.
• Insect repellent – regular use of a permethrin-based repellent such as Switch or Deosect is the most effective fly and midge repellent. It is also important to apply fly repellent cream or gel to areas of the body not covered by rugs such as the sheath or teats.
• Regular bathing – to relieve symptoms, prevent scurf build up and keep the coat shiny and slippery which reduces the midges ability to grip to the horse to bite them.
• Keeping away from water – there will be more midges in areas near to water courses so affected horses should be kept away from these areas.

During a flare up or in more severely affected horses some veterinary treatments are indicated on top of the management strategies such as:

• Steroids – a course of steroids can be useful to reduce inflammation and itchiness.
• Medicated creams – prescription creams containing steroids and antibiotics can be used on targeted areas where the skin is worse affected or broken.
• Immunotherapy – targeted vaccinations against the midge saliva injected under the skin in a series of injections which can reduce the horse’s symptoms.
• Insol – a vaccination originally made for ringworm has been found to improve sweet itch symptoms in some horses when given just ahead of the midge season.