Equine Proliferative Enteropathy: Developing a Challenge Model (AAEP 2010)

It isn't every day that a new disease or ailment is discovered, as many of the most common equine health problems have been around for several decades, if not centuries. But within the past decade a new disease has emerged that appears most frequently in weanlings. The disease is equine proliferative enteropathy (EPE), a gastrointestinal disease that causes excessive weight loss and stunted growth in foals.

Because veterinarians only recently discovered EPE, little research has been completed on it. But Allen E. Page, DVM, of the University of Kentucky, has developed a challenge model for EPE, a breakthrough that he discussed at the 2010 American Association of Equine Practitioners Convention, held Dec. 4-8, 2010, in Baltimore, Md.

The bacterium Lawsonia intracellularis is the causative bacterial agent for EPE, which is characterized by diarrhea, depression, fever, inappetance (anorexia), weight loss, edema (fluid accumulation in the skin) of the throat latch, ventral abdomen, or lower limbs, a poor hair coat, and intermittent colic (due to thickening of the mucosal lining in the small intestine). Most of the knowledge that equine veterinarians possess about this disease is from the research that has been done in swine, in which L. intracellularis was noted long before it appeared in horses.

The disease typically is not fatal, providing that a diagnosis is made early and the foal receives proper medical treatment. Even then, however, the foal likely will have suffered severe weight loss and stunted growth; affected foals might have a smaller overall stature than unaffected ones, although research into this aspect of EPE is lacking.

In order to study EPE in a controlled manner, Page designed the challenge model whereby he administered L. intracellularis, isolated from a previous case of EPE, to six weanlings through a nasogastric tube. The challenged weanlings were monitored daily for signs of EPE with samples (fecal and blood) collected for analysis at regular intervals. The team also performed weekly ultrasounds to check for thickening of the intestinal walls, and they weighed the foals on a weekly basis. At the end of the study Page and colleagues performed a necropsy on each of the weanlings, examining the small intestine for signs of L. intracellularis infection since this is where the bacteria typically infect the horse.

Of the six weanlings that were challenged with L. intracellularis, four contracted forms of EPE based on analysis of all of the data that was collected during the study. Page added that one of the foals was affected subclinically (the horse did not show any outward clinical signs of disease). The remaining two weanlings showed no signs of EPE, which is consistent with real-world cases where weanlings are exposed to the L. intracellularis, but never develop EPE.

Page added that larger challenge studies are needed to help further researchers' understanding of EPE and the bacterium that causes it.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.