Horses that recover from Lawsonia intracellularis infections cost less as yearlings than their siblings, but they race just as well, reported Michele L. Frazer, DVM, Dipl. ACVIM, of Hagyard Equine Medical Institute in Lexington, Ky. Frazer presented a study on the subject during the 2009 American Association for Equine Practitioners (AAEP) Convention, held Dec. 5-9 in Las Vegas, Nev.

The bacterium L. intracellularis is the causative bacterial agent for equine proliferative enteropathy (EPE), which is characterized by diarrhea, depression, fever, inappetance (anorexia), weight loss, edema (fluid swelling) on the abdomen or lower limbs, a poor hair coat, and intermittent colic due to thickening of the mucosal lining in the small and large intestines. Weanlings that are 4 to 7 months old are most commonly affected.

"It is generally accepted that horses infected with L. intracellularis that develop EPE do survive, but the long-term effects of this disease remained relatively unexplored," explained Frazer.