Listeria in Sheep

Listeria in Sheep
This disease is a bacterial infection. Listeria monocytogenes is a bacterium present in the soil everywhere (ubiquitous organism). Grass being made into silage is often contaminated with small amounts of soil and therefore contains listeria. If the silage is not well ensiled (pickled) and the pH does not drop below 4.5 then the bacteria can survive and multiply. This is particularly the case if there are pockets of air in the silage, a common problem with baled silage. There are two distinct disease patterns with listeria, the enteric and the encephalitic form. It will also cause generalised septicaemia with abortion in pregnant ewes. The enteric form causes diarrhoea and can be mistaken for salmonella. The diagnosis can only be made by ruling out salmonella and then at postmortem with histology of the infected gut areas. The encephalitic form causes circling and blindness and is more common in young animals who are changing their teeth. The bacteria in the mouth enter the tooth roots and travel to the brain where they cause an encephalitis. Affected animals can be treated with antibiotics and anti-inflammatories and in the early stages of the disease treatment may be successful. Talk to your veterinarian about the best treatments to use.

All ruminants can suffer from listeria. Prevention is better than cure, so to feed only well-ensiled silage that does not have soil contamination and has had an inoculant used to improve the preservation will help. Unfortunately, sheep and goats are particularly susceptible to listeria and it may be that the best way to avoid the problem is not to feed them baled silage!

Date Added: Thursday, 29th April 2021


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