Allergies affect animals as much as humans – horses unfortunately are no different. Some are particularly allergic to the saliva in the bite from a Culicoides fly causing a condition known as Sweet Itch. This means that once a sensitive horse has been bitten by this particular midge, it will have an allergic reaction at the site of the bite. This will cause a localised irritation which the horse will scratch in an attempt to alleviate the itching. This however causes a never-ending cycle - by scratching himself, the horse only self-inflicts further damage. Sweet Itch can affect any horse or pony, although as a guideline symptoms normally begin to show between the ages of 1 and 5.
There are many different species of Culicoides midge, and each one prefers to bite a different part of the horse. The horse will then scratch the area around where the fly has bitten. Most common are the “dorsal feeders” that bite, and cause damage around the horse’s ears, poll, mane, withers, rump, and tail head. However in more severe cases they can also be affected by “ventral feeders”, which are generally less common. They tend to cause itching around the horse’s face, chest, and belly.
Due to the life cycle of these specific flies this is a seasonal disorder, as indicated above, characterized by severe itching. The horse in question may become restless, rubbing himself against trees or fences, and will keep swishing his tail in an attempt to ward off the flies. Other symptoms include hair loss as a result of rubbing against objects, flaky dandruff, skin thickening, weeping sores or dried yellow crusts. Early on in the disease, the skin will be bald, red, inflamed, crusting and sore. As the disease progresses, the skin becomes chronically thickened, blackened, and wrinkled and the hair becomes sparse and coarse. The tail becomes thinned and hard taking on an almost rat-tailed appearance. Over the winter, a horse may recover completely, only to find himself at square one when spring hits and he comes into contact with the flies yet again.
Regrettably, once a horse develops an allergic reaction to the Culicoides fly bite, there is no cure. Sweet Itch will occur every year so the comfort and wellbeing of the horse lies in the hands of the owner and how he/she manages the condition.
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