Health

Genetics: The New Frontier: Part 4

The equine genome map is as important to the future of horses as the development of antibiotics was 45 years ago.

This is the last of a four-part series. Need to review Part 1, Part 2 or Part 3?

Dr. Martin Furr, chief of medicine at the Marion duPont Scott Equine Medical Center at Morven Park in Leesburg, Virginia, has completed work on a new diagnostic test to identify a pattern of activity in circulating white blood cells that would indicate an active EPM infection. The beauty of this diagnostic tool is that during the acute stage of infection, it would allow Dr. Furr to discern active disease from casual exposure or antibody response to the EPM vaccine.

“We developed a diagnostic signature for EPM that proved highly accurate, at least in the acute phase of infection – up to 28 days,” Dr. Furr says.

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When this research is completed, the genomic biomarkers are expected to be able to provide information on the stage of disease and the prognosis, as well as a means to monitor the progression of the disease and its response to treatment.

Simple Test, Complex Ethics

Genetic testing for diseases and inheritable traits is simple and inexpensive – about $40. Most tests require either a blood sample or a hair sample with the root bulb attached. Turnaround time is about three weeks.

“It can determine diseases, colors, gender, identity and parentage,” says Dr. Melba Ketchum, director of Shelterwood Laboratories in Timpson, Texas. “You can use it for forensics – anything that is genetically based. We can do all those types of tests on this array.”

Even if the horse owner is not aware of the horse’s parentage, the test can provide that information if the parents’ DNA profiles are in the database.

Dr. Ketchum, a longtime equine genetics researcher participating in the equine genome project, says the array technology especially is a boon for horsemen who breed for specific hair-coat color.

“If you’re going for different colors, you can manipulate that quite easily with the test. It’s all laid out right there in front of you,” she says.

The current array technology Shelterwood uses can flag four diseases. A new array will have 10 diseases on the chip.

What to Do?


With this knowledge comes an ethical question: Should certain horses that carry markers for a specific disease be banned as breeding stock to eradicate those problems from the breed?

“Once you know that an animal might be carrying a gene for susceptibility, do you or do you not want to breed your mare to that horse? That’s a very touchy issue,” Dr. Edward Robinson, director of the equine pulmonary laboratory at Michigan State University, says.

Dr. James Michelson, professor of veterinary biosciences at the University of Minnesota, says most scientists try to remove themselves from the debate over the ethics of continuing to breed horses that carry genes for disease.

“We, for the most part, try not to take sides in this,” he says. “It’s up to the horse owners and their breed associations to use this information as best they can. We do our best not to push one school of thought onto them.

“I think it’s clear that most of us would say that we’ve spent a lot of time and the American Quarter Horse Association has funded us to do this research to improve the health and well being of horses.

“We’ve done our part and identified these genes and made these tests available. We encourage people to use these tests, but it’s up to the association to make their bylaws and their guidelines.”

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