Lawsonia intracellularis, a bacterium causing equine proliferative enteropathy (EPE) in mostly young horses, can result in thickening segments of small intestines and sometimes large intestines. L. intracellularis does not grow in routine aerobic/anaerobic culture and can only grow in vitro (in the lab) in cell culture, which is not practical. Therefore, several quick and reliable PCR tests have been developed to directly detect the bacteria.

Besides horses, L. intracellularis infects pigs and many other domestic and wild animals, including hamsters, rabbits, foxes, deer, ferrets, ostriches, and non-human primates. Previous studies have shown that a variety of wild and domestic animals, including dogs, cats, rabbits, opossums, skunks, mice, and coyote, shed L. intracellularis on farms with diagnosed EPE cases. Fecal-oral transmission of L. intracellularis has been documented in naïve foals housed with clinically infected foals experimentally challenged with an equine isolate of L. intracellularis (Pusterla et al 2010).

Clinical signs of EPE include depression, anorexia, fever, peripheral edema (fluid swelling of the throat latch, sheath, and distal limbs), hypoproteinemia (low blood protein levels), hypoalbuminemia (low levels of the protein albumin in the blood), weight loss, colic, and diarrhea in affected foals. Early clinical signs are generally unspecific and include mild depression, partial anorexia, and fever. Signs of EPE might resemble those of other gastrointestinal disorders such as parasitism, bacterial infections (Clostridium spp., Salmonella spp., Neorickettsia risticii), rotavirus, coronavirus, ulcerations, sand accumulation, intestinal obstruction, and intoxication with plants, chemicals, and pharmacologic agents such as non-steroidal anti-inflammatory drugs or antimicrobials (Pusterla and Gebhart, 2013). Therefore, treating veterinarians should rule out other diseases with diagnostic tests.

Practitioners generally make a presumptive EPE diagnosis based on age of the affected animal, hypoproteinemia/hypoalbuminemia, fever, and presence of thickened small intestinal loops on ultrasonographic evaluation