Listeriosis is a bacterial infection that affects many animals including humans. The disease is more commonly seen in sheep (most commonly), goats and cattle.
The gram positive bacteria, Listeria monocytogenes, are very resistant and can survive in the environment for a long time. They can replicate at temperatures ranging from 4-44°C.
The bacteria is ubiquitous to the environment being found in soil, sewage, bedding, water and food - replicates on poorly kept silage.
Disease is more commonly seen in winter months when more silage is being fed.
Clinical signs – very varied!
- Anorexia, depression and disorientation
- Propulsive behaviour – find them with their heads stuck in gates
- Head press into corners
- One sided facial paralysis – drooping ear and lip, lowered eyelid, drooling
- Infection is usually of one side of the brain, hence the one sided appearance
- Impacted food in cheek due to paralysis of chewing muscles
- Abortions – usually late gestation
- Causes inflammation and infection of the placenta
- Thorough clinical examination.
- If suspected in cases of abortion then dam blood, foetus and placenta need to be submitted for investigation as to the cause.
Needs aggressive treatment with antibiotics. Higher than normal doses are required to allow crossing into the brain.
Supportive treatment with fluids and electrolytes will help those finding it difficult to drink and feed.
Good silage management, make sure there are no holes in the wrapping (repair ASAP if there are any) and don’t feed any spoiled silage to the animals.
Make sure feed and water troughs are clean
Avoid soil/faecal contamination of feed and water
Addition of additives to silage to alter the pH and reduce Listeria replication
Fence of silage from farm stock and vermin to reduce damage to bail wrapping.