Lawsonia intracellularis: An emerging disease (Proceedings)

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Lawsonia intracellularis: An emerging disease (Proceedings)

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Apr 01, 2010

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)
     o SOUTH AMERICA
     o AUSTRALIA
• 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
• SEROLOGICAL ASSAY
     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

Treatment
• Supportive Care
     o Nutrition (TPN)
     o Secondary Infections
     o Fluids
     o Colloids
          • Hetstarch 10ml/kg IV
          • Plasma 10-20 ml/kg IV
• ANTIBIOTICS
     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