Lawsonia intracellularis, an emerging pathogen, is known to be the cause of EPE. The study cites rodents, birds, insects, soil and dogs as possible sources of the pathogen, and says a fecal-oral route of spread is probable, but research is continuing into in those areas.
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, was undertaken after four herd outbreaks were reported in Canada and others on farms in central Kentucky. Frazer examined medical records of 57 horses treated at Hagyard for L. intracellularis infection between August 2005 and January 2007.
Her study found that the infected horses: - Ranged in age from 2 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.
- 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
The study advises practitioners that young horses with those 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 when 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.