Continued from previous page.
Finding researchers with complementary interests and expertise can be a challenge, the veterinary researchers say.
"You have to keep up to date with the literature in both veterinary and human medicine, as well as in the major scientific journals," said Sharon Spier, a UC Davis veterinary professor who studies and treats horses. "You also have to keep up with research presented at major medical meetings and keep talking with colleagues who are working in similar areas."
Through such efforts, Spier developed a cross-country collaboration with a medical researcher that led to discovery of the cause of a disease known as "hyperkalemic periodic paralysis," which afflicts both humans and horses.
Spier began studying the disease about a decade ago. Two Quarter Horses had been donated to the school for research, both with symptomatic muscle tremors and periodic total collapse. No one knew whether the affliction was rooted in the muscles, nervous system or perhaps the kidneys.
Spier bred the donated mare and stallion and, by using embryo transfer techniques, established a breeding line of horses with the disease. Through her work with researchers in the campus veterinary and medical schools, she identified the disease as a problem of the muscle cells. Then, while scanning the literature, she ran across a summary of a research paper presented by medical researcher Eric Hoffman of the University of Pittsburgh, who was studying a similar disease in humans. Hoffman had found that in humans a genetic flaw upsets the flow of sodium through the membrane of muscle cells, disrupting the electrical balance in the cells that is so crucial for muscle control.
Spier's studies confirmed that the same defect was at work in the affected horses. She began corresponding with Hoffman, who assigned a medical student in his laboratory to work on identifying the genetic mutation from samples of horse muscle tissues that Spier provided.
The research team found that the mutations were similar in humans and horses, but occurred in different locations within the muscle sodium channel. After identifying the mutation, the researchers were able to develop a genetic test for the disease. Now horse owners simply send in blood samples to the UC Davis Veterinary Genetics Laboratory, and for $35 they can find out if their horses carry the genetic mutation. Since 1992, the campus lab has performed 35,000 such tests. Spier and colleagues hope that breeders will use the information and refrain from breeding affected horses.
Meanwhile, research continues in humans and horses to determine why patients exhibit such dramatic differences in clinical severity of the disease, ranging from no symptoms at all to death. The researchers also have adapted some studies from human medicine and begun treadmill tests with affected horses to determine how likely they are to experience episodes while being ridden. And the researchers are studying drugs that might be used to control the disease.
Tracking a disease from obscurity to diagnosis was particularly rewarding, Spier said. And the collaborative efforts with researchers in human medicine were key to efficiently unraveling the secrets of the disease, she added.
