PUBLIC HEALTH WATCH V-1226 FOCUS ON AGRICULTURE Listeriosis caused by the bacterium Listeria monocytogenes

Neil W. Dyer The disease in humans The disease in ruminants DVM, DACVP • Opportunistic infection of: (cattle, sheep and goats) Director, NDSU Diagnostic Laboratory – Elderly • Encephalitis (infection of the Charles L. Stoltenow – Pregnant women central nervous system). DVM, DACVPM – Unborn – “Circling disease” – caused by Extension Veterinarian brain involvement – Neonates – Immunosuppressed • Abortion (infection of the uterus Listeriosis is an infection of human and or the fetus). animal importance. It is caused by • Pregnant women may experience a – Generally during the last two Listeria monocytogenes, a bacterium mild infection (flu-like symptoms) months of gestation because widely distributed in the environment. which can spread to the fetus and of production practices In particular it can be found in soil, lead to intrauterine death or a water, a variety of foodstuffs, and feces of severe neonatal infection. – Occurs in winter healthy animals and people. It is capable – Infections early in pregnancy are – Associated with consumption of causing disease in humans, animals treatable of spoiled silage or spoiled hay and birds. The bacterium can survive – Infections in late pregnancy – Animals that abort are resistant in soil or silage for up to two years. may cause death of the fetus or to reinfection It is capable of growing in a wide variety problems in the development of foods under a number of different • Septicemia (infection of the blood). of the nervous system environmental conditions such as high – Primarily occurs in young – Surviving infants show salt concentration, acid environment, animals long-term problems and refrigerator temperatures. However, – Can be exhibited by sudden – Some neonates develop late it cannot survive the pasteurization death process. Because of the prevalence of onset blood infections in 10-12 L. monocytogenes in the environment days • Conjunctivitis (infection of the and its ability to cause disease in – Most often the bacteria affects: tissues around the eye). humans and animals, knowledge * Pregnant uterus • Mastitis (infection of the mammary about this organism is important * Central nervous system gland). to the agricultural community. * Bloodstream – The bacteria can be shed in milk • Non-pregnant individuals can – Shedding can persist for more develop meningitis or septicemia. FEBRUARY 2002 than three years • Adult mortality varies with • Pneumonia (infection of the lung). conditions.

North Dakota State University Fargo, North Dakota 58105 The disease in EXPOSURE POINTS! Prevention • Food-borne (oral) — primary monogastric animals Individuals who may be at risk means of transmission. (pigs, dogs, cats, rabbits, should take appropriate food safety small mammals) – Foods with high water content precautions. and neutral pH • Usually see a septicemia and/or * Soft cheeses, dairy products • Ensure safety of food of animal sudden death. * Pâtés, sausages, smoked fish origin. • May see uterine infections and * Salads – Pasteurize or cook raw products abortions as well. * Ready to eat products (con- (milk) taminated after pasteurization) • Wash raw vegetables before eating. – Contaminated milk (raw or The disease in birds contaminated after pasteuriza- • Thoroughly cook beef, pork and • More severe in young birds. tion) poultry. • Septicemia * Bacteria excreted by ruminants • Wash hands, knives and cutting with Listeria mastitis boards (do not cross contaminate). – Clinical signs of emaciation, diarrhea • Direct contact with infected • Avoid use of untreated manure tissues — veterinarians and • Encephalitis on vegetable crops. livestock producers at risk. – Clinical signs of central nervous – Bacteria may be excreted by – Ruminant abortion cases system disease ruminants – Sudden death in neonatal • Take precautions in handling ruminants aborted fetuses, sick or dead – Central nervous system disease animals. in adult ruminants – Mastitis (milk) samples – Contaminated ocular (eye) swabs – Infection during the neonatal period due to use of contami- nated equipment between neonates/infected animals

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