Dairy cow with listeria

Listeria and Humans

Listeria is common in the environment and poses a particular risk to vulnerable groups of consumers e.g. the elderly, the very young, pregnant women and those with compromised immune systems), so very strict control measures are followed to ensure Listeria species do not contaminate dairy products.

Listeria and livestock

What to look for 

  • Nervous signs - paralysis of muscles, restlessness and/or walking in circles
  • Fever
  • Pregnant cows may abort
  • Death may occur within 2-3 days

Cause – a bacterial infection (Listeria monocytogenes)

Listeria can cause serious disease in a wide range of animal species and in humans, but rarely causes illness in cattle. This bacteria is widespread in the dairy environment (in soil, water, feed) and survives in a wide range of conditions including poorly made or spoiled silage. There are no simple tests to identify feed that is contaminated by Listeria.

Animals likely to be affected

Listeriosis can infect cattle of any age but is most often seen in young adult cattle. It rarely infects animals under six months of age. If several animals have access to the same contaminated feed source there may be an outbreak of Listeria, but the disease does not generally spread from animal to animal.

Other diseases with similar signs

Other causes of abortion or nervous signs.

Confirming the diagnosis

A post-mortem examination will allow your vet to collect brain samples that can be examined at a laboratory for the characteristic changes caused by Listeria.

Risks to people

Most Listeria infections in humans result from eating contaminated food, but it is very important that people practice good personal hygiene when handling sick or dead animals.


Antibiotics and other supportive therapies can be useful if Listeria is detected early.

Risk factors

  • feeding poorly made or spoiled silage

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