Coping with SweetItch
(By Pauline Williams, BSc, MSc,MA,VetMB, Cert EM (Int Med), MRCVS)
Sweet itch is a skin condition caused by an allergic reaction to midge bites (primarily Culicoides spp). It is also known as insect bite hypersensitivity or summer seasonal recurrent dermatitis, and can affect horses, ponies and donkeys all over the world according to the distribution of midges.
All animals are bitten by midges but only those that are allergic to the bites show clinical signs. There are different species of Culicoides which feed at different sites; some at the mane and withers, others at the tail and or belly and legs. The animal may be allergic to one or more species and therefore they may show signs on one area only, such as the tail or all over the body in severe cases.
Affected animals show varying degrees of pruritis (itchiness) which leads to self-trauma due to rubbing. The most common sites affected are the mane and tail but sometimes only the belly is affected and in severe cases the animal may show signs of all over the body including the legs. Rubbing leads to alopecia (hair loss), ulcers and bleeding with secondary crusts (scabs) and infection. Many of these changes are reversible out of season when there are much fewer midges. However in more chronic cases the skin can become hyper pigmented (blackened) and thickened with ridges, especially along the mane. Severely affected animals may lose weight due to chronic irritation and show behavioural changes from tail swishing, rolling, and rubbing the belly on the ground to being unrideable at the peak midge feeding times of the day (dusk and dawn).
If you are buying a pony that is said to be managed successfully by one of the different treatment options, you should be aware that a change in location may either improve or exacerbate the condition to a point that it is no longer manageable. Sweet itch sufferers may also deteriorate with age.
When buying a pony in the winter out of the midge season, in severe cases the thickening on the neck and tail head may still be evident. However, it is often difficult to detect animals which show milder signs or those that have been managed effectively through the summer. Often there is evidence of different hair length, particularly at the tail head, but it is important to ask the owners to declare if the pony suffers from the condition. At present, there is no reliable blood test or other allergy test to detect sweet itch sufferers out of season, but research is on-going.