Equine Proliferative Enteropathy

Equine proliferative enteropathy (EPE) is a gastrointestinal disease that results in thickened intestine and slower growth for weanling horses. EPE is caused by Lawsonia intracellularis bacteria, a microbe better known from the swine industry where slowed growth means smaller pigs being sent to market. More cases are being reported among horses, but the larger number may be due primarily to an increased awareness of the disease and better diagnostic techniques.

The disease is most commonly seen in foals from four to seven months old, and often appears shortly after the young horses are weaned. Affected foals may seem only slightly sick but may become very ill with weight loss, diarrhea, mild colic, depression, edema, and low blood protein. Seriously ill foals can die.

Surviving weanlings seem to be immune after recovery, but usually they have fallen behind the growth rates of their healthy herd-mates. As sale time approaches, they tend to be thin, small, and rough-coated, not the best bet for catching the eye of a prospective bidder. One study found that affected foals tend to sell for less at public auction, but go on to have similar race winnings as their peers.

Diagnosed early in the course of the disease and treated with antibiotics, most young horses make a steady recovery and eventually regain lost weight. Because some foals fail to show clear signs of the disease, it’s easy to overlook the first cases of illness in a weanling herd. Managers can keep a close eye on newly weaned horses, watching for mild indications of disease such as elevated temperature, diarrhea, horses going off feed, or mild edema in the legs, belly, or jaw. Fecal analysis can be done to detect shedding of Lawsonia, and blood tests can determine protein and antibody levels. If one weanling is diagnosed with EPE, managers should monitor the others in the herd closely for signs of the disease and be prepared to have other foals tested. Diarrhea and fever can have other causes, so a diagnosis is important before starting treatment.  Ultrasound examination is helpful to detect and monitor progression of thickened intestine.