This disease primarily affects piglets, weaners and growers. The key clinical signs include septicaemia; pneumonia; head to one side.

Background and history

This is caused by the bacterium Listeria monocytogenes which may colonise the tonsils and be passed out in faeces.

Listeria are wide spread in nature and are often found in cheese and silage.

Exposure results in infection but disease is uncommon.

Clinical signs

  • The bacterium may cause a septicaemia and high temperature in piglets.
  • Nervous signs, possibly meningitis.
  • Weak piglets at birth.
  • Pneumonia.
  • Head on one side.
  • Middle ear infections.


Laboratory examinations are necessary for diagnosis. Polymerase chain reaction (PCR) tests are used.


  • Stress causing the bacteria to invade the system.
  • Porcine reproductive and respiratory syndrome (PRRS).
  • Flu.
  • Heavy environmental exposure


  • Listeria are usually sensitive to penicillin and ampicillin.
  • In outbreaks it is necessary to identify the sources of infection and reduce the exposure to them.