Drug compounding, the ethics of treating cryptorchids, and sexually transmitted diseases were the hot topics discussed by equine practitioners at the Reproduction Forum, led by Steven Brinsko, DVM, PhD, Dipl. ACT, associate professor of theriogenology at Texas A&M University, and Mats Troedsson, DVM, PhD, Dipl. ACT, of the University of Florida.

Drug Availability

Ovuplant, an ovulation-induction agent containing deslorelin acetate, has not been available in the United States since 2003. It is not expected to return to the market, meaning practitioners have to continue to find different options for deslorelin. As there is no FDA-approved product containing deslorelin for use in horses, it can legally be compounded.

Crytorchidism

Forum leaders raised the question of ethics in treating cryptorchid horses–is treatment doing the horse any good? Are veterinarians propagating the cryptorchidism in horses by treating the condition? Or are the owner’s finances the only benefit of treating these horses?

The heritability of cryptorchidism in horses is unknown, although studies in other species suggest the condition is highly heritable, and practitioners are aware that certain breeds (e.g. Percherons, Welsh ponies) are more susceptible. Some breed registries dictate the ethics of cryptorchidism by culling horses with the condition from breeding programs.

Forum leaders questioned whether it is correct to treat this condition, given that it appears to be passed on to the stallion’s progeny. Additionally, testicles retained in the abdominal cavity are incapable of normal spermatogenesis due to the elevated temperature and more prone to neoplasia (cancer).

Contagious Equine Metritis

In October 2006, two stallions returned positive test results for contagious equine metritis (CEM) during a breeding soundness test, the first U.S. cases since 1998. They bred test mares in 2004 during the importation process, and were certified to be clean. Following exposure to those mares, they were bred. So how did they contract it, and how did they pass quarantine? And are there more positive cases like these in the country?

Attendees discussed the current importation testing procedure, and considered possible alternative solutions, including the use of polymerase chain reaction (PCR) tests.

One forum attendee cited a study performed in Iceland, where horses have never been exposed to CEM. Researchers performed PCR tests on stallions and found 30% were positive for CEM, raising the possibility that there are pathogenic and non-pathogenic strains of the virus.

Because of these high positive PCR results on unexposed horses, PCR testing was considered too sensitive to use as the sole test for use in imported horses.

Equine Viral Arteritis

Attendees also discussed the outbreak of equine viral arteritis (EVA) in New Mexico and Utah in 2006. This outbreak occurred within the Quarter Horse racing industry.

It was noted that since the outbreak, many stallions and pregnant mares have been vaccinated, and most of major Quarter Horse racing farms are vaccinating all their horses, potentially signaling a shift in the way horse owners and veterinarians approach the disease.

Although many people vaccinated against the disease, very few precautions were taken at shows and events. It is possible for a stallion to pick EVA up via the respiratory route, and then shed the virus for the rest of his life. Forum attendees suggested stallion advertising should start declaring, “guaranteed tested and vaccinated for EVA,” as mares can be protected via vaccine.

It was suggested that the disease could be better controlled or even eliminated if all colts and serologically negative stallions were vaccinated.

Get research and health news from the American Association of Equine Practitioners 2006 Convention in The Horse’s AAEP 2006 Wrap-Up sponsored by OCD Equine. Files are available as free PDF downloads