Genetic Influence for Sarcoids in Horses

Equine sarcoids are common skin tumors in horses. Small sarcoids are usually harmless, but large tumors are unsightly and may get in the way of tack or harness. The exact cause of sarcoids has not been determined, though there is strong evidence of a link to bovine papilloma virus. Even after treatment with drugs or surgery, sarcoids tend to recur in many horses.

Researchers at the Swiss Institute of Equine Medicine conducted a study of 222 Swiss Warmblood horses from two half-sibling sire families. All horses were visually assessed and classified as unaffected, mildly affected, or severely affected with sarcoids. They were then genotyped, and quantitative trait locus statistical analysis was used to identify chromosomal regions containing genetic variants that could be associated with the development of, or resistance to, equine sarcoids. These included genes that regulate immune response and replication of viruses.

Identification of horses with a genetic pattern that favors the formation of sarcoids could help breeders select mares and stallions with a lower probability of developing the tumors. Likewise, genetic testing for sarcoid susceptibility might influence a prospective buyer to favor one horse over another.