A researcher has found a reliable way to diagnose equine protozoal myeloencephalitis (EPM) in the acutely affected horse by examining genetic markers in its blood. This technique could potentially be applied to detect evidence of other infectious diseases before clear clinical signs appear.

Martin Furr, DVM, Dipl. ACVIM, PhD, professor of internal medicine and chief of medicine at the Virginia-Maryland Regional College of Veterinary Medicine, presented information on his study examining the microarray gene chip analysis technique at the 2005 American Association of Equine Practitioners Convention, held Dec. 3-7 in Seattle, Wash.

“This method is a way to assess the expression of several genes all at one time,” Furr explained. “It’s a very new technique and sort of earth-shattering technology.” He used a gene chip–a 1.2 cm-square membranous disk with a grid that has about 500,000 potential spots to place gene probes, which detect the expression of particular genes in the horse. There were around 3,000 probe sets on the type of chip he used. Each set probes the DNA in a blood sample for a particular gene’s expression.

Theoretically, different diseases should have different patterns or “signatures” of expression. “The combination of genes and strength of signal represent the signature we’re looking for in our sample,” he said. “We will generate a database comprised of normal and diseased horses. When our diagnostic signature matches the diagnostic signature for one of our referenced diseases, then we have a confirmed diagnosis