Case-histories study aims to improve diagnosis of EPE, halt outbreaks

LEXINGTON, KY. — A retrospective study of 57 horses treated for proliferative enteropathy (EPE), or protein-losing enteropathy, aims to help equine practitioners make a timely diagnosis of the disease and provide key signals that might help prevent outbreaks.

Lawsonia intracellularis, an emerging pathogen, is known to be the cause of EPE, but little is known about its source and how it is spread. Four herd outbreaks in Canada and others on farms in central Kentucky are mentioned in the study, which cites rodents, birds, insects, soil and dogs as possible sources of the pathogen, and says a fecal-oral route of spread is probable, though research in those areas is ongoing. The pathogen infects cells lining the small intestine and causes them to expand and elongate, resulting in protein loss (hypoalbuminemia), weight loss and poor body condition.

The retrospective study, authored by Michele Frazer, DVM, Dipl. ACVIM, a practitioner at Lexington's Hagyard Equine Medical Institute, examined medical records of 57 horses treated at Hagyard for L. intracellularis infection between August 2005 and January 2007.

The study found that the infected horses:

» Ranged in age from 2 months to 8 months

» Presented between August and January

» Had at least two of five clinical signs – ventral edema, fever, colic, diarrhea and lethargy – with ventral edema being the most common, occurring in 81 percent of the horses

» All had hypoalbuminemia

» Did not always test positive for L. intracellularis by fecal polymerase chain reaction (PCR) or a blood test

» Had good survival rates, with 53 surviving, three dying of secondary complications and one euthanized at the owner's request because of a grave prognosis

» Were sold for 68 percent less as yearlings than comparable uninfected yearlings.

A sex predilection was not apparent because a similar number of fillies and colts presented. And although all but one horse was a Thoroughbred, that was considered a reflection of the breed population seen at the clinic and not a breed predilection for the infection, Frazer reported.

The study advises practitioners that young horses with the above signs should be considered potentially infected with L. intracellularis. Tests such as abdominal ultrasound of the ileum and small intestine, PCR and serum tests should be performed and, if a positive diagnosis is made, treatment can include antibiotics, synthetic colloids and/or plasma transfusions, according to Frazer.

The study was published in the Journal of Veterinary Internal Medicine 2008;22:1243-1248.