Listeriosis

Listeriosis is caused by several species of Listeria, bacterial organisms that live as saprophytes in the environment but occasionally cause disease in a wide range of vertebrates including mammals, marsupials, birds and reptiles. These organisms are most often ingested in food, where they can proliferate even at refrigeration temperatures. Most illnesses are caused by Listeria monocytogenes, but L. ivanovii is found occasionally, and there are rare reports of clinical cases caused by other species of Listeria. In humans, L. monocytogenes is most important as a cause of pregnancy losses in healthy women, and septicemia or central nervous system (CNS) disease in people who are immunosuppressed, debilitated, newborn or elderly. Clinical cases are uncommon in healthy, nonpregnant people and the associated syndromes are not usually life-threatening; however, rare serious illnesses can have a high case fatality rate, as listeriosis may not be suspected and the appropriate treatment may be delayed. Sporadic clinical cases and outbreaks of listeriosis are also seen in animals. They occur most often in herbivores fed silage, but carnivores and omnivores can also be affected. As in humans, reproductive losses, CNS disease and septicemia are the most serious syndromes. Predisposing factors for listeriosis are poorly understood in animals, and many affected animals seem to be healthy.