Sweet (or summer) itch

Source: uu.nl
Tail and mane eczema is an allergic reaction which can make many horses and ponies miserable. Although no good medication has been found for this condition, extensive research has provided us with a wealth of information.
The large-scale, five-year study was conducted by researchers from Wageningen University and the Utrecht University Faculty of Veterinary Medicine. Support was provided by Technology Foundation STW, Koepel Breeding Association and Artu Biologicals.

Tail and mane eczema is also known as summer eczema. It is a horse’s allergic reaction to the bite of Culiocoides insects, or midges. Substances in midge saliva cause intense itching; sensitive horses react by rubbing along objects, which in turn causes various problems.

In the course of five years, data was collected from more than 10,000 horses. This data makes it clear that approximately 20% of the susceptibility to tail and mane eczema is genetically determined. This heredity is a complex process involving several genes. Research on those specific genes is being continued in another project, HORSEGENE.

Also investigated were the specific proteins (allergens) in the midge that cause the severe reactions. Eight such allergens were identified, and a blood test was developed which can demonstrate the allergy in 9 out of 10 affected horses. The allergens can also be produced artificially, which could make possible the development of immunotherapy. This type of therapy involves repeatedly administering the allergens and other substances, so that the immune system ‘learns’ to react less severely.