What is listeriosis?

  • Caused by the bacterium listeria monocytogenes.
  • Grows well in less acidic pH of spoiled silage (pH >5.0). 
  • Outbreaks occur around 14-21 days after feeding poor quality silage.

Economic implications?

  • Less than 2% clinically involved in an outbreak.
  • Mortality rate greater than 70%.
  • In exceptional circumstances, may reach 10% of a flock. 

Clinical signs?

  • Not eating.
  • Depressed, disoriented.
  • Propel themselves into corners, fences, under gates and feed troughs.
  • Leans against objects.
  • Profuse salivation.
  • Food material impacted in the cheek of the affected side.
  • Drooping ear, deviated muzzle, flaccid lip on the affected side.
  • Lowered eyelid on the affected side.
  • Weakness along affected side of body.

Differential diagnoses?

  • Pregnancy toxaemia in heavily pregnant ewes.
  • Peripheral vestibular lesions (middle ear infections).
  • Brain abscesses.
  • Gid (coenurosis, tapeworm cyst in the brain).


  • Based upon a thorough veterinary examination. 


  • Early detection of illness is a must. 
  • Prompt, aggressive antibiotic treatment prescribed by your vet. 
  • High doses of antibiotic.
  • Oral propylene glycol to prevent development of a severe energy deficit. 
  • Fresh palatable foods and clean water must always be available. 
  • A topical antibiotic eye ointment should be applied twice daily.

Prevention and control?

  • Discard spoiled silage (or feed to cattle).
  • Clean feed troughs on a daily basis.
  • Avoid soil/manure contamination of feed troughs from tractor wheels etc.
  • Discard refusals.
  • Clean water troughs regularly.

Silage making?

  • Use proven silage additives.
  • Silage clamps must be rolled continuously and sheeted to prevent entry of air.
  • Use a block cutter.
  • Cut across a narrow silage face.
  • Seal punctures immediately.
  • Fence against farm stock and vermin.

(This guide is courtesy of the National Animal Disease Information Service)