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Basics ⬇

Outline

BASICS

Overview!!navigator!!

PE is a transmissible enteric disease caused by Lawsonia intracellularis, an obligate intracellular Gram-negative bacterium. It affects a number of animal species and has a worldwide distribution. A fecal–oral transmission and spread via drinking water and food are suspected. The incubation period of the disease is believed to be 2–3 weeks in foals. Isolated cases are most common but outbreaks do occur.

Signalment!!navigator!!

  • Foals 4–7 months of age are most susceptible, although it may also affect young adults
  • No breed predisposition, but colts are possibly more commonly affected

Signs!!navigator!!

  • May be asymptomatic and self-limiting
  • Growth retardation, lethargy, fever, anorexia, weight loss, ventral edema, diarrhea, and colic are common. Concomitant conditions such as upper or lower respiratory tract infection, intestinal parasitism, gastric ulcers, and dermatitis are common in severely affected foals

Causes and Risk Factors!!navigator!!

Weaning is a predisposing factor.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Parasitism, gastroduodenal ulcers, sand impaction, acute intestinal obstruction, infiltrative bowel disease including neoplasia (lymphoma), eosinophilic gastroenteritis, and intoxication with plants and chemicals, including pharmacologic agents such as NSAIDs
  • Infectious diarrhea caused by Salmonella spp., Rhodococcus equi, Clostridium spp., Neorickettsia risticii, Campylobacter jejuni, and rotavirus

CBC/Biochemistry/Urinalysis!!navigator!!

  • Hypoproteinemia/hypoalbuminemia
  • Occasionally, leukocytosis, neutrophilia, hyperfibrinogenemia, increased creatine kinase, hypocalcemia, hyponatremia, azotemia, and anemia

Other Laboratory Tests!!navigator!!

  • Serology using immunofluorescence may help confirm exposure to the bacteria. Serology may be positive when the clinical signs are first detected, and foals may remain seropositive for more than 6 months
  • Positive PCR on feces will confirm the presence of L. intracellularis in the intestine. However, fecal excretion of L. intracellularis detected by PCR ends soon (<4 days) after the beginning of an effective antimicrobial administration. Positive PCR on feces may be present in horses of all ages without EPE
  • L. intracellularis does not grow on conventional bacteriologic media

Imaging!!navigator!!

Abdominal ultrasonography often reveals thickening of segments of the small intestinal wall.

Other Diagnostic Procedures!!navigator!!

N/A

Pathologic Findings!!navigator!!

  • Marked thickening of the small intestinal mucosa, giving its surface an irregular and corrugated appearance
  • Thickened mucosa and severe hyperplasia of crypt epithelium
  • Silver-stained sections reveal numerous short and slightly curved bacterial rods in the apical cytoplasm of the immature epithelial cells.
  • Diagnosis is confirmed by immunohistochemistry
  • Ulcerative and necro-hemorrhagic enteritis may also be observed

Treatment ⬆ ⬇

TREATMENT

  • Less severely affected foals may be treated as outpatients
  • Transfusion of fresh or fresh-frozen plasma may be required in foals with severe hypoproteinemia
  • Additional symptomatic treatment such as antiulcer therapy, IV crystalloid or colloid fluid therapy, and parenteral feeding are indicated in some cases

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Erythromycin estolate (15–25 mg/kg PO every 8 h), or azithromycin (10 mg/kg PO every 24 h), or clarithromycin (7.5 mg/kg PO every 12 h) alone or combined with rifampin (rifampicin) 10 mg/kg PO every 12–24 h), administered for 2–3 weeks
  • Doxycycline (10 mg/kg PO every 12 h) and chloramphenicol (50 mg/kg PO every 6 h) may also be viable options
  • Drugs should also target concurrent infections when present

Contraindications/Possible Interactions!!navigator!!

Rifampin may decrease the intestinal absorption of clarithromycin.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • A rapid improvement in clinical signs is observed in most foals, following administration of appropriate antimicrobials
  • Hypoproteinemia may take up to a month to resolve

Prevention/Avoidance!!navigator!!

  • Passively acquired antibodies do not appear to be protective for EPE
  • Environmental contamination by fecal shedding from infected foals is likely to be minimal once antimicrobial treatment is initiated

Possible Complications!!navigator!!

N/A

Expected Course and Prognosis!!navigator!!

Prognosis is favorable with therapy unless necrotizing enteritis or severe concurrent medical complications are present.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Marked hypoproteinemia may lead to thromboembolic diseases.

Age-Related Factors!!navigator!!

Weaning time is a predisposing factor, suggesting that ration changes, mixing, and transportation may contribute to EPE.

Zoonotic Potential!!navigator!!

PE is not currently considered to be a zoonosis, although it affects nonhuman primates.

Abbreviations!!navigator!!

  • EPE = equine proliferative enteropathy
  • NSAID = nonsteroidal anti-inflammatory drug
  • PCR = polymerase chain reaction
  • PE = proliferative enteropathy

Suggested Reading ⬆ ⬇

Pusterla N, Gebhart CJ. Equine proliferative enteropathy—a review of recent developments. Equine Vet J 2013;45:403–409.

Author(s) ⬆

Author: Jean-Pierre Lavoie

Consulting Editors: Henry Stämpfli and Olimpo Oliver-Espinosa