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Feed-based allergy treatment shows promise

A modified feed could help control cases of "sweet itch" in exported Icelandic horses.
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Research from Iceland suggests that genetically altered feed may help control insect hypersensitivity in the country’s native horse breeds.

An Icelandic horse with a very lush forelock and mane.

Icelandic horses sent to other countries have a high incidence of "sweet itch." 

Icelandic horses sent to other countries have a high incidence of “sweet itch,” an intense allergic reaction to the saliva of biting midges (Culicoides spp.). The breed is predisposed to this allergy because the insects responsible aren’t found in Iceland, so horses there have no opportunity to develop a normal immune response to their bites.

To determine whether a specially modified feed might help manage or prevent Culicoides allergy in horses, researchers at the University of Iceland grew barley that had been genetically altered to produce a protein similar to one found in the saliva of the midges. Then they fed flour produced from that barley to four Icelandic horses. In addition, three horses were fed flour made from unaltered barley to serve as controls. After the horses ingested seven doses of the altered flour, the researchers analyzed samples of their blood and saliva for the presence of antibodies.

They found antibodies to the midge allergen in samples from all of the treated horses. What’s more, there were signs that the antibodies could act upon the allergens, which suggests that they might minimize the horse’s immune response outside of the laboratory setting. 

The researchers call for additional studies to explore whether feed-based treatments are a viable option for horses with insect hypersensitivity. 

Reference: “Oral administration of trans- genic barley expressing a Culicoides allergen induces specific antibody response,” Equine Veterinary Journal, December 2016 

This article was originally published in Volume #475 of EQUUS magazine

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