Monitoring and Preventing Equine Proliferative Enteropathy

As with many infectious diseases, it's preferable to prevent equine proliferative enteropathy (EPE) rather than treat it. This emerging disease, which is caused by the bacterium Lawsonia intracellularis and infects foals and weanlings worldwide, has placed significant financial burden on parts of the equine industry, but horse owners and managers can prevent its spread. Nicola Pusterla, DVM, PhD, Dipl. ACVIM, an associate professor in the Department of Medicine and Epidemiology at the University of California, Davis, shared some important prevention tactics to this end.

EPE Before

An EPE-affected foal (above), and the same foal after recovery (below).


Equine proliferative enteropathy causes the mucosal lining in a weanling's small and large intestine to thicken, resulting in reduced absorption of nutrients and a loss of protein from the body (via the gastrointestinal system). Clinical signs can be indefinite but might include slow growth, weight loss, fever, depression, poor appetite, edema (fluid swelling), and/or occasional diarrhea and colic. The disease generally isn't fatal.

Pusterla explained that veterinarians diagnose EPE through a combination of clinical signs, low blood protein levels, the detection of L. intracellularis antigen in feces through polymerase chain reaction testing, and/or L. intracellularis antibodies in blood serum.

What can be tricky about the illness is that "previous research has shown that healthy foals with no sign of EPE can shed the bacterium, exposing susceptible foals to the bacterium," said Pusterla. "Thus, infectious disease control measures are mandatory to prevent the spread of disease from an infected to a susceptible horse."

Pusterla added that horse owners should be familiar with the signs of the disease, separate foals with confirmed EPE from the rest of the herd (to avoid disease spread via fecal-oral transmission) and prevent wild animals--which veterinarians suspect might have a role in disease transmission--from accessing horses' feed and feeding areas.

According to Pusterla, "It is also advisable to test herdmates to determine whether they have been exposed or not and to conduct daily clinical monitoring to recognize animals in the early stages of disease."

Additionally, Pusterla noted that standard biosecurity and infection control strategies could help minimize the spread of EPE.

"Minimizing stress during weaning and ensuring foals are dewormed appropriately (might) also help prevent EPE," he added.

Currently, there is no commercially available vaccine for L. intracellularis. However, Pusterla and colleagues are in the process of testing a rectally administered vaccine for foals.

"Preliminary results are promising, but the cost of the vaccine may be high for some farms and routine monitoring of vaccinated foals will still be necessary," said Pusterla.

Pusterla described what to look for when working with a veterinarian to monitor the presence or spread of EPE on a farm:

  • When testing herdmates of infected animals, if a horse's antibody levels (a measure of how the horse is responding to the pathogen) against L. intracellularis are greater than or equal to 60 by immunoperoxidase monolayer assay (IPMA) and the protein level is normal, the horse was likely exposed to the bacterium, but did not develop EPE. In this case regular monitoring is still advised;
  • If the antibody levels are greater than or equal to 60 and the horse does have a low protein level, then additional tests are needed to rule out EPE; and
  • Veterinarians do not advocate treating foals suspected of having EPE based on antibody and protein level alone, due to potential adverse side effects associated with using the recommended antibiotics for L. intracellularis.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.