LISTERIOSIS can be a killer disease for Scottish sheep flocks and is almost entirely preventable by taking greater care when feeding.

The economic implications for flock owners can be considerable. Mortality can be as high as 70% and can reach 10% of a flock.

In this article, the National Animal Disease Information Service (NADIS) highlights symptoms and prevention.

CAUSE:

- Caused by the bacterium listeria monocytogenes

- Grows well in less acidic pH of spoiled silage (pH under 5.0)

- Occurs around 14-21 days after feeding poor quality silage

CLINICAL SIGNS:

- Not eating

- Depressed, disoriented

- Propel themselves into corners, into fences, under gates and feed troughs

- 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

SILAGE MAKING:

- Use silage additives

- Continuous rolling of silage clamps

- Sheet clamps to prevent entry of air

- Use a block cutter

- Cut across a narrow silage face

- Seal punctures on wrapped big bales immediately

- Fence-off wrapped bales

DIFFERENTIAL DIAGNOSES:

- Pregnancy toxaemia during the last four weeks of pregnancy

- Middle ear infections

- Brain abscesses

- Gid (coenurosis, tapeworm cyst on the brain)

Diagnosis based upon thorough veterinary examination

TREATMENT:

- Early detection of illness

- Prompt aggressive antibiotic treatment prescribed by the vet

- High doses of antibiotic

- Oral propylene glycol to prevent development of a severe energy deficit

- Fresh palatable foods and clean water

- Antibiotic eye ointment twice daily

PREVENTION/CONTROL:

- Discard spoiled silage, or feed to cattle

- Clean feed troughs daily

- Avoid soil/manure contamination of feed troughs from tractor wheels etc

- Discard refusals

- Clean water troughs regularly