Sweet itch or Summer Seasonal Recurrent Dermatitis (SSRD) is a disease of the immune system that can affect all breeds and types of horses, ponies and donkeys. It is 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. Therefore, sweet itch is prevalent between April to October when the midges are active.
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.
- Intense itching (severe pruritus).
- The horse may swish its tail vigorously in an effort to keep the flies away.
Itching can become so severe that the horse 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 excessively and scratch at their mane with their hind hooves.
- 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.
- Weeping sores, sometimes with a yellow crust of dried serum (exudative dermatitis) 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 midges. 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.
Prevention and control
There is no cure for the disease and once a horse develops sweet itch it recurs every year.
Prevention and control consist of controlling the horse’s environment and could include:
- Try to avoid marshy, boggy fields as midges thrive in them. A more exposed windy site, chalk-based grassland and grazing that is well drained may have fewer midges.
- Midges thrive in warm and moist conditions such as on droppings. Poo picking regularly may help to reduce midge breeding grounds and keep your muck heap away from grazing and stabling to help reduce the amount of midges near your horse.
- Water troughs should be cleaned regularly to prevent flies from breeding there.
- Sweet itch rugs which cover all the areas of the horse susceptible to bites can provide protection.
- Stabling horses at night from dusk to dawn, when midges are at their most active, can help prevent horses being bitten. Although, stabling can do more harm than good due to the hard surfaces the horse can rub on.
Ways to ease the itching:
- Soothing lotions will relieve the itching and reduce inflammation but they will not deter further midge attacks.
- Insect repellents and insecticides (containing pyrethrins or pyrethroids) may help to deter midges from biting.
- Benzyl benzoate can be a good deterrent, but it has to be constantly reapplied.
- Insect repellents should be applied well before signs develop and should not be applied to inflamed or broken skin. All insect repellents and insecticides should be applied with care.
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