Lawsonia intracellularis

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