Listeriosis

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Overview, Causes, & Risk Factors

Listeria monocytogenes is common in wild animals, domesticated animals, and in soil and water. L. monocytogenes causes disease in many animals and is a common cause of miscarriage and stillbirth in domestic animals. L. monocytogenes also occurs as a food-borne contaminant that can cause disease.

In humans, L. monocytogenes most often causes a generalized blood infection (septicemia) or meningitis (inflammation of the covering of the brain). The fetus, newborn, and pregnant women are particularly susceptible to L. monocytogenes. Immunocompromised individuals, such as those being treated for cancer, those with organ transplants, and those with AIDS are at increased risk.

Infection of a pregnant woman early in pregnancy generally leads to miscarriage. The organism may be transmitted across the placenta. Infections in late pregnancy may lead to stillbirth or death of the infant within a few hours of birth. About half of infants infected at or near term will die.

In infants, listeriosis may become evident in the first few days of life with loss of appetite, lethargy, jaundice, vomiting, respiratory distress, and shock. Infants usually have pneumonia. A skin rash may be present. The death rate is very high.

Late-appearing infection in the infant (symptoms appear at age 5 days or older) and infection in children is often seen as meningitis. There are no special clinical signs to differentiate listerial meningitis from other types of meningitis.

In adults, the disease may take many forms depending on what organ or organ systems are infected. It may occur as meningitis, pneumonia, septicemia, and endocarditis or in milder form as abscesses, skin lesion, and conjunctivitis.