Actinobacillus lignieresii

• Pathogenesis and pathogenicity:
  • Commensal in the mouth and intestinal tract of cattle and sheep
  • Penetrates damaged mucosa to cause chronic granulomatous inflammation of soft tissues, a condition known as Actinobacillosis
  • Enodogenous, sporadic infection
  • Lesions in the tongue, cheek, lips and sometimes in the lower gut and lungs from aspiration
  • Often spreads from the site of infection to lymphatics, and may cause pyogranulomatous lymphadenitis
  • Myositis and formation of fibrous tissue in the lesions lead to hardening of the tissue, hence the condition is known as 'wooden tongue' in cattle
  • In sheep abscesses with thick walls are produced
  • Feeding is impaired, causing loss of condition
  • Infection in the oesophageal groove can cause tympany and enlargement of the retropharyngeal lymph node, causing difficulty in swallowing and breathing
  • Cutaneous lesions in cattle and sheep
  • Contamination of the environment via ulcerating lesions
• Diagnosis:
  • Induration of tongue
  • Tissue sections may demonstrate pyogranulomatous foci containing club colonies
  • Gram negative rods may be present in smears from exudates
  • Cultures on blood agar and MacConkey agar, incubated for 24-72 hours
  • Blood agar: small, sticky, non-haemolytic clonies
  • MacConkey agar: slow lactose fermentation
• Treatment:
  • Sodium iodide parenterally, or potassium iodide orally
  • Potentiated sulphonamides or a penicillin/streptomycin combination
  • Rough feed should be avoided