Listeria monocytogenes

• Outbreaks of listeriosis caused by L. monocytogenes seasonal and linked to silage feeding
• Replicates in poor quality silage where the pH excedes 5.5
• Animals highly susceptible during pregnancy due to lowered cell-mediated immunity
• Neural listeriosis:
  • Incubation period 14-40 days
  • Meningoencephalitis
  • Dullness, circling, head tilt, facial paralysis, drool saliva, droop of eyelid and ear
  • Exposure keratitis
  • Fever during early stages
  • Recumbency and death within a few days in sheep and goats
  • Abortion up to 12 days after infection in cattle; usually recover but may get septicaemia
• Septicaemic listeriosis:
  • Incubation period 2-3 days
  • Lambs and occasionally pregnant sheep
  • Occurs in newborn piglets, foals, poultry, adult sheep
• Keratoconjunctivitis in cattle and sheep - direct contact with silage via eye
• Pneumonia, myocarditis, enodcarditis
• Zoonosis - consumption of contaminated unpasteurised milk; memingitis and meningoencephalitis; abortion