Listeriosis

Cause

Listeria monocytogenes, a bacterium.

Description

Listeria is widespread in the environment. People, other mammals, birds, fish, crustaceans and insects can be infected.

Where the disease occurs

Listeria is found worldwide with clinical disease in animals occurring more commonly in temperate climates than tropical or sub-tropical climates.

The disease in animals

Listeriosis is primarily a disease of ruminants, particularly sheep, and the major clinical signs are encephalitis and abortion. Pigs and horses can develop septicaemic disease occasionally. In the farm environment, listeria has been isolated from water troughs, manure, soil and animal feeds. It is commonly present in silage. Risk factors such as poor nutritional status, sudden changes in climate and transport can predispose to infection of animals.

Control of disease in animals

Control is difficult because of the ubiquitous occurrence of the organism. Vaccines are available but their efficacy needs further evaluation. Antibiotic treatment may be successful if begun early in the course of the disease.

How people can get the disease

The disease is quite rare in people, with about two human cases per million occurring annually.

The disease can be contracted from other people who are carrying the disease, domestic and wild animals, poultry, soil, fish, crustaceans, vegetables, water, contaminated foodstuffs, sewage and mud. Most healthy people eat foods that contain small amounts of listeria with no apparent illness.

Listeriosis has a wide range of effects in people. Inflammation of the brain commonly occurs in adults with headache, chills, fever, myalgia, nausea and vomiting which can precede neck stiffness, convulsions, and possibly stupor and death. It is particularly serious in pregnant women and their infants, older people and immuno-compromised individuals. Premature, stillborn or acutely ill infants may be born to infected mothers.

Treatments for people

Antibiotic treatment can be successful although newborn infants have a high mortality rate despite treatment. 

Preventing the disease in people
  • Pregnant women and other susceptible people should avoid contact with potentially infected animals.
  • They are also advised to avoid high-risk foods such as chilled ready-to-eat foods, raw seafood and un-pasteurised dairy products.
  • People handling aborted animal foetuses, particularly from sheep and cattle, should use protective equipment.

Further information

Last updated 27 September 2012