Lawsonia Infection in Foals: No Negative Effect as Adults (AAEP 2009)

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.


Dr. Michele Frazer explains L. intracellularis and the prognosis for affected horses.
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To better evaluate the impact of EPE in horses, Frazer reviewed the medical records of Thoroughbred horses diagnosed at Hagyard Equine Medical Institute with L. intracellularis infections between January 2002 and January 2008.

"The sale and race records from these horses were compared to average sale and race records for all progeny by the same sire as the affected horse," relayed Frazer.

Of the 116 horses included in the study, 36 were sold at public auction as yearlings. The sale price of these horses at public auction was significantly lower than the average sale price of the sire's progeny. In contrast, the monetary earnings of the 30 horses that raced were not significantly different from the average monetary earning' of the sire's progeny.

"These findings suggest that the athletic potential of horses which have recovered from Lawsonia intracellularis infections does not seem negatively affected, despite the fact that they command lower sale prices than other yearlings," concluded Frazer.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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