Particularly active during the summer months (April to October), Sweet Itch or Summer Seasonal Recurrent Dermatitis (SSRD) is a disease of the immune system that affects all breeds and types of horses, ponies and donkeys. Caused initially by an allergic reaction to midge bites, the horse’s immune system reacts to a protein in the midge’s saliva which causes the immune system to attack its own cells and leads to the extreme allergic reaction.
Culicoides midges usually feed along the dorsal surface (back) of the horse including the head, mane, withers, rump and dock (tail) and clinical signs are often first seen in these areas.
- Severe pruritus (intense itching)
- The horse may swish its tail vigorously in an effort to keep the flies away
Itching can become so severe that it scratches itself on anything in reach including posts, stable doors and trees.
- Excessive mutual grooming from field companions is common
- Horses have been known to roll, scratch at their mane with their hind hoofs and bite their own tail
- Hair loss
- The skin can become bald, inflamed, crusty and sore
- As the condition progresses skin thickens, becomes wrinkled and the hair becomes sparse and coarse with flaky dandruff.
- Exudative dermatitis (weeping sores, sometimes with a yellow crust of dried serum) may also develop
- Change in the horse’s temperament
- Lethargic with frequent yawning or agitated and impatient, with a lack of concentration when ridden.
- A horse may also shake its head or become restless if flying insects are close by.
During the winter months, a horse’s skin may totally recover. However the disease often returns in the spring at the first contact with flies. It is therefore essential for owners to be aware of the potential risk of purchasing a horse during the winter months when there are little or no signs of sweet itch.
If a horse has a mane and tail that look suspicious, it is advisable to inspect it closely for signs of hair loss which may suggest sweet itch in the summer.
Prevention and control
There is no cure for the disease and once a horse develops sweet itch it recurs every summer proving a management nightmare for its owner.
Prevention and control consist of controlling the horse’s environment and should include:
- decreasing the horse’s exposure to the Culicoides midges
- killing the flies that do attack the horse
- stopping the itching.
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