Sweet itch is an allergic condition in horses characterised by itching, particularly on the base of the mane and over the tail. The consequent severe rubbing of the affected areas causes skin damage and dramatic hair loss. It can be seen in any age of horses and often develops at a relatively young age, becoming progressively worse as the patient gets older. Once a horse has developed the allergy, it is likely to be affected every year.
Sweet itch is caused by an allergy to the bites of various insects. The primal cause in the UK is a small culicoides midge, although various insects can cause similar problems in other parts of the world. These insects feed primarily at dawn and dusk. They are less active during the night and not at all active during the middle of the day. They are also less active during windy days than during still days, and breed in ares of moist, muddy ground around ponds, marshes, ditches and so on.
Management of the condition is aimed mainly at avoiding exposure to or control of the midges. These are rarely active when the temperature is less than 10°C, limiting the condition to late spring, summer and early autumn.
In most cases this means turning horses out after 10am and getting them in before 4pm, thereby avoiding the most active feeding times for insects. In severe cases fine mesh screens can be fitted to stable doors and windows to avoid the insects getting into the stables, although this is usually less of a problem as the midges don’t usually invade accommodation in significant numbers. If practical, ditches and ponds can be drained, and this removes some of the breeding grounds. The midges are also more active in wooded areas, and so avoiding grazing horses near water courses or wooded areas will help to reduce the problems seen.
Night stabling of affected animals should begin before the onset of the insect season and continue until the insects start to die off in the autumn. A single night’s exposure to the insect population can trigger an itching session that can last for two or three weeks. Where this is not practical, rugs are available which cover the poll, full length of the neck and are tied around the abdomen and cover most of the tail, however this is not an ideal solution.
Insect repellents may help to control the symptoms. There are a number of permethrin based repellents on the market, which seem to offer better control than others. However, no perfect insect repellent exists, and reliance on insect repellents alone is unlikely to give a satisfactory control of the condition. The weekly application of ‘Switch’ may also help in controlling the midges.
If your horse or pony has sweet itch, control of further damage is by using the avoidance programme already discussed. Benzyl Benzoate, a topical insecticide applied direct to the skin, also has a mild insect repelling action. Bacterial infections fueling the damage may need to be treated with antibiotics. If you have concerns and require advice please contact us for more information on this condition.