Lawsonia intracellularis: An emerging disease (Proceedings)


Emerging intestinal disease of the in the horse, referred to as Eequine proliferative enteropathy.

Lawsonia intracellularis

• Obligate intracellular curved, Gram Negative Bacterium

     o Apical Cytoplasm of the intestinal enterocytes

     o Crypt

Emerging intestinal disease of the in the horse

     o Referred to as Equine Proliferative Enteropathy

• Disease primarily of pigs until the 1980s.

• Increased caseload in central Kentucky in the 2000s..

• Many Species : domestic and wildlife

     o Pigs

     o Hamsters

     o Rabbits

     o Fox

     o Deer

     o Ferrets

     o Ostriches

     o Non-Human Primates

• Horses : First Reported in 1982

• World Wide Distribution

     o USA

     o CANADA

     o EUROPE (England, Belgium, Switzerland)



• Majority of cases are in Foals 2-8 month of age

     o Few adult cases reported

Characteristics of Lawsonia

• Microaerophilic / anaerobic

• Genetically related to the sulfate-reducing bacteria, except...

     o Obligately intracellular

     o Causes proliferation of enterocytes

     o Sulfate reduction not demonstrated

• Vibrio-shaped with a single polar flagellum

Clinical signs

• Ventral Edema

• Fever

• Colic

• Diarrhea

• Lethargy

• Weight loss

Seasonal omponent

Horses presented in the fall or early winter

Clinical pathology

• Hypoproteinemic

     o Low Total Protein

     o < 5.0 mg/dl

• Hypoalbuminemic

     o < 2.0 mg/dl

Abdominal ultrasound

• May reveal segments of thickened small intestine

     o Not very sensitive

Diagnostics (ante-mortem)

• Fecal Culture

• Not Practical

• Fecal PCR: Evaluated in Pigs

     o Sensitivity : Variable (39-72%)

     o Specificity : High (100%)

     o HORSES?

          • Early Clinical Cases

          • Not good for Subclinical Cases

          • Not good for Prolonged Cases


     o IgG

     o Employ LI cultured in Enterocytes

     o OR

     o Preparation of LI on slides as Antigens

          • Staining of the bacteria either by flourescent (IFA) OR

          • Peroxidase Labeled

               • (Immunoperoxidase monolayer assay)

     o POSITIVE > 1:60


• Supportive Care

     o Nutrition (TPN)

     o Secondary Infections

     o Fluids

     o Colloids

          • Hetstarch 10ml/kg IV

          • Plasma 10-20 ml/kg IV


     o Macrolides

          • Erythromycin, Azithromycin (10mg/kg PO SID), Clarithromycin (7.5mg/kg PO BID)

     o Tetracyclines

          • Doxycycline 10mg/kg PO BID

          • Oxytetracycline 6.6 mg/kg IV BID

     o Chloramphenicol 50mg/kg PO TID to QID

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