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What is listeriosis?

Listeriosis is a disease caused by eating food contaminated with the Listeria monocytogenes bacteria.

Where are Listeria bacteria found?

These bacteria are found in soil, food for horses and cattle, water, mud and silage. They can also live in domestic and wild mammals, fowl and people. The bacteria may pose a risk for illness if soil and manure used as fertilizer contaminate vegetables or if animals contaminate meats and dairy products.

Who gets listeriosis?

Anyone can get listeriosis; however, the disease is not common in children, young adults, and others with healthy immune systems. Unborn babies and newborns, pregnant women, persons who have weak immune systems (due to cancer, diabetes, or organ transplant, for example), and the elderly are the persons most likely to get this disease.

What are the symptoms of listeriosis?

The disease may be mild or serious. Mild illness includes fever and muscle aches and sometimes nausea or diarrhea. In newborns and adults with weak immune systems, infection may spread to the nervous system or bloodstream and cause sudden fever, intense headache, and stiff neck and confusion, loss of balance, and convulsions.

Healthy children and adults may not have any symptoms. If a woman is infected while pregnant, she may not feel very sick, but may have a premature delivery or even lose the baby as a result of infection. A baby can also be infected during the last trimester of pregnancy or during birth, and become ill in the first three weeks of life.

How soon after exposure do symptoms appear?

The symptoms generally appear about 3 weeks after exposure but may appear as soon as 3 days or as long as 70 days after exposure.

How is listeriosis spread?

Consuming raw or contaminated milk, soft cheeses, unwashed raw vegetables, undercooked poultry, and ready to eat meats (like cold cuts) can cause infection. Infection can also be transmitted from a pregnant woman to her baby in the womb or during birth. The organism enters the body through the mouth, but then tends to affect the central nervous system. Healthy people may consume contaminated foods without getting ill.

For how long can an infected person carry the bacteria?

Infected humans can shed the organism in stool for several months. Mothers of infected newborn infants may shed the bacteria in vaginal discharges and urine for 7-10 days after delivery. The bacteria are not easily passed from one person to another, however, so this disease is not considered to be very contagious.

What is the treatment for listeriosis?

Penicillin or ampicillin used alone or with other medications are used to treat listeriosis. Antibiotics may be given to infected pregnant women to prevent illness in the baby.

How can listeriosis be prevented?

  1. Pregnant women and immunocomprised persons should avoid soft cheeses, such as feta and Brie; heat all leftovers and ready to eat foods, such as hot dogs, until steaming hot; and consider either avoiding deli meats or heating them before eating.
  2. Thoroughly cook meats and poultry. Keep uncooked meats separate from vegetables and cooked foods.
  3. Avoid raw milk and other unpasteurized dairy products.
  4. Thoroughly wash raw vegetables before eating them.
  5. Practice proper handwashing to prevent the bacteria from entering the mouth. Wash knives, cutting boards, and kitchen surfaces after uncooked foods contact them.

Last Updated: 09-28-2011

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