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).
Diagnosis?
- Based upon a thorough veterinary examination.
Treatments?
- 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)
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