Equine Proliferative Enteropathy

What is Equine Proliferative Enteropathy? 

Equine proliferative enteropathy (EPE) is an enteric disease caused by the obligate, intracellular bacterium Lawsonia intracellularis. The disease causes intestine inflammation and thickening.

Clinical Signs: Clinical signs of ventral edema, diarrhea and hypoalbuminemia combined with the time of year and age of the horse can be almost pathognomonic for EPE. North American cases are most commonly seen in August through January with young horses between two and eight months of age most commonly represented. Clinical signs may include:

  • Anorexia (partial or complete)
  • Rapid weight loss
  • Dependent/ventral edema (typically head, legs, and prepuce)
  • Rough hair coat
  • Fever
  • Colic
  • Diarrhea
  • Depression

Diagnosis: A presumptive diagnosis of EPE can be made based on hypoalbuminemia coupled with clinical signs, age, and season. Testing to confirm a diagnosis of EPE includes:

  • Hypoalbuminemia: This is a consistent finding across almost all cases of EPE and always accompanied by hypoproteinemia.  
  • Abdominal ultrasonography: Used to identify areas of small intestinal wall thickening (>5mm), the absence of thickening does not rule out EPE.
  • Fecal PCR testing: Utilized to demonstrate the presence of L. intracellularis in the gastrointestinal tract.  False negative results are possible, especially once antimicrobial therapy has started.
  • Serologic assays: Several different assays exist, all of which detect antibodies to L. intracellularis.  Ideally, paired samples 7-14 days apart will be submitted, but many will initiate therapy based on a single positive result at the time of clinical signs and other testing.  In certain geographic areas, exposure to the bacteria can approach 100%, so serologic diagnosis should always be paired with clinical signs and other diagnostic options.
  • CBC and biochemistry analysis: These findings are typically mild in normal cases of EPE, although leukocytosis, hyperfibrinogenemia, and increased hematocrit have been reported.  However, severe leukopenia, neutropenia, thrombocytopenia, and other changes have been associated with necrotizing-EPE, which often results in sudden decompensation and euthanasia/death.

Treatment: Treatment for EPE consists of antimicrobial treatment and supportive care. The most commonly used antimicrobials include tetracyclines (oxytetracycline, doxycycline, minocycline) or chloramphenicol. The antimicrobial choice should reflect the age of the animal and the risk for gastrointestinal or renal toxicity.

Prevention: While limited studies have described immunization of foals via rectal administration of the porcine vaccine against Lawsonia intracellularis, this represents an off-label use of the product and practitioners are advised to check their state rules regarding whether it is acceptable to vaccinate animals with vaccines labeled for another animal species.