Lawsonia intracellularis
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Overview
- Causes porcine proliferative enteropathy
- Grows intracellularly in porcine enterocytes
- Excreted in small amounts in faeces of infected pigs
Characteristics
- Slender, curved, Gram negative rod
- Microaerophilic
- Obligate intracellular bacterium
- Requires enterocyte tissue culture for growth
Pathogenesis and pathogenicity
- Affinity for porcine enterocytes
- Causes proliferation of enterocytes
- Adenomatous and inflammatory lesions develop in the terminal ilium, caecum and colon
- Synergistic relationship between L. intracellularis and intestinal flora including E. coli, Clostridium species and Bacteroides species
- Intestinal organisms may produce correct oxygen tension and conditions for colonisation of L. intracellularis
- Infection can only take place in presence of intestinal flora
Clinical disease
- Proliferative enteropathy occurs in weaned pigs, 6-12 weeks old
- Chronic intermittent diarrhoea with reduced growth or acute haemorrhagic enteropathy
- Sudden death in severe infections
- Recovery from mild form in most animals without treatment
- Post mortem lesions include thickened wall, mucosal necrosis with clotted blood in the lumen of the ilium, caecum and colon
- Enlarged mesenteric lymph nodes
Diagnosis
- Clinical signs and pathology give a presumptive diagnosis
- Organisms demonstrated in faeces or ileal mucosa by immunofluorescence or PCR
- Silver impregnation stains or immunostaining or lesions
- Culture in enterocyte cell lines
Treatment and control
- Antibiotics such as tylosin, tiamulin used prophylactically or therapeutically in feed/water
- Zinc bacitracin in feed
- Thorough cleaning and disinfection of premises
- Brachispira hyodysenteriae(Principles of Microbiology Notes (Bacteriology) p. 85).