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What is it?

Listeriosis is a bacterial disease caused by the bacteria Listeria monocytogenes. These bacteria are found naturally in soil, groundwater and plants, and can also be found in feed for horse and cattle and silage. Infected domestic and wild mammals, fowl and people can carry these bacteria.

How is it spread?

Listeria is spread by consuming contaminated food or drink. Foods commonly associated with listeriosis include raw milk, soft cheeses, raw vegetables, smoked fish, and ready-to-eat meats such as cold cuts and pâté.

What are the symptoms and when do the occur?

Symptoms will appear on average 3 weeks after exposure to the bacteria, although it can range from 3 to 70 days. Most people who are exposed to Listeria bacteria will only have an acute mild illness with fever. For the immunocompromised, the elderly, and those with debilitating illnesses are more likely to experience severe symptoms including intense headache, nausea and vomiting. In some cases, septicaemia (infection of the blood) or meningoencephalitis (infection of the brain and the covering of the brain), collapse and shock may occur. Pregnant women can pass the infection on to the fetus, resulting in stillbirth, pre-term delivery, infant septicaemia and meningitis.

When is a person infectious?

Listeria is not spread person-to-person, however an infected person can shed the bacteria in their feces for several months

How can I protect myself and prevent the spread?

  • Thoroughly wash raw vegetables and fruit before eating.
  • Thoroughly cook all poultry products to 74° C/ 165° F or 82° C/ 180°F for whole poultry. Cook all meat and meat products to 71° C/ 160° F.
  • Wash hands with soap and water after using the toilet, diapering, and before and after preparing food.
  • Avoid the use of untreated manure on vegetable and fruit crops.
  • Veterinarians and farmers must take proper precautions in handling aborted fetuses and sick or dead animals, especially sheep that have died of encephalitis.
  • Higher risk groups such as pregnant women, the elderly, and those who are immunocompromised should avoid smoked fish and seafood, unpasteurized milk and dairy products, and soft cheeses. Leftovers and ready-to-eat foods like pâté, hotdogs, deli meats and luncheon meats only be eaten if they are heated until steaming hot.

Listeriosis must be reported to the Medical Officer of Health as per the Health Protection and Promotion Act.
For more information, please contact a member of Haldimand-Norfolk Health Unit’s Infectious Disease Team.

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