Veterinary Physiology

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Current Epidemiologic Status and Public Health Importance of Listeriosis: A Review

Sadik Zakir , Sufian Abdo, Mustafa Mohammed Bushra, and Johar Aliye Hussein School of Veterinary Medicine, College of Agriculture and Veterinary Medicine, Jimma University, Jimma, Ethiopia * Corresponding author: Sadik Zakir, School of Veterinary Medicine, College of Agriculture and Veterinary Medicine, Jimma University, Jimma, Ethiopia. Email:


Listeriosis is a bacterial disease caused by different listeria species, among which Listeria monocytogenes are the most pathogenic species of ruminant animals and humans. This paper aimed to review current updates on the epidemiology and public health significance of listeriosis. The disease is an acute central nervous system infection, with associated abortions occurring in pregnant cattle. Reservoirs of infection are the soil and the intestinal tracts of asymptomatic animals, including wild and feral mammals, birds, and fish. Listeria, like other infections, occurs through ingestion as well as inhalation or direct contact and venereal transmission. In animals, listeriosis typically occurs after the consumption of contaminated silage or other feed sources. Consequently, contaminated food sources, such as raw meat and fish, unpasteurized dairy products, and uncooked vegetables, are good sources of infection in humans. The major clinical forms of listeriosis in cattle are encephalitis, abortion, Mastitis, iritis, The major clinical forms of listeriosis in cattle are encephalitis, abortion, mastitis, ophthalmitis, and keratoconjunctivitis phthalmitis, iritis and keratoconjunctivitis. The disease can be tentatively diagnosed based on clinical symptoms, and its confirmation is achieved through serological tests and blood culture. Listeriosis shares similar clinical signs with other diseases, such as rabies, Coenurosis, and Scrapie. Response to antibiotic therapy may be poor in neural listeriosis. Prolonged high doses of ampicillin or amoxicillin combined with aminoglycosides may effectively prevent listeriosis in animals. Generally, disease prevention heavily depends on the protection of animal feed and vaccination. Moreover, humans are recommended to avoid eating and drinking uncooked meat and unpasteurized milk products.


Listeriosis is a bacterial disease caused by different Listeria species; among them Listeria monocytogenes (L. monocytogenes) being the most pathogenic species of ruminant animals and humans1. The other two species, Listeria ivanovii and Listeria innocua, are less frequently considered as animal disease agents2. Listeria monocytogenes is a Gram-positive, rod-shaped, motile bacterium. It is classified in the Family Listeriaceae, and there are six listeria species within this phylogeny. Listeria monocytogenes has been recognized as a human pathogen since 1929; however, the transmission route was reported in the 1980s when a series of food-related outbreaks were found3. The organism can grow over a range of temperatures from 4 to 45°C and tolerate PH values between 5.5 and 9.6. In such circumstances, L. monocytogenes may reach 1° colony forming units (CFU) per kilogram of silage. The bacteria have a group of genes that allow invasion, survival, multiplication, and mobility in the intracellular environment. The organism resists freezing and thawing, and can survive for several years in feces, straw, silage, and soil4. Listeria monocytogenes is pathogen that causes listeriosis and most commonly isolated from soil and silage in the environment. In foods, it has been found in raw or processed food samples, including dairy products, meat, vegetables, and seafood5. Listeriosis is an emerging infection with major public health concerns due to associated food-borne outbreaks and significant risk of morbidity and mortality. Large food-borne outbreaks of listeriosis have occurred during the last decade in Europe

and the USA1. During 1991-2002, 19 outbreaks of invasive listeriosis infection were reported in 9 European countries, with a total of 526 related cases. In 1997, one large outbreak resulting in 1,566 cases of listeria gastroenteritis was reported in Italy and traced to the consumption of contaminated corn salad. A recent nationwide outbreak linked to contaminated packaged meat products occurred in Canada in 2008, resulting in 56 patients, including 20 deaths6. Transmission of L. monocytogenes is principally via fecal-oral route through the consumption of contaminated food, raw or contaminated milk, vegetables, and ready-toeat meat have been the cause of worldwide outbreaks. Food may be contaminated by L. monocytogenes during preparation and it then multiplies during the storage process. Unlike some other food borne pathogens, L. monocytogenes can multiply in contaminated refrigerated food7. Once the pathogen gains entry into mammalian cells by phagocytosis, they are released from the membranebound vacuole and begin to multiply. The pathogen uses actin polymerization for intracellular movement and cellto-cell spread infecting a vast range of host tissues, with the liver being the main site of infection8. Meningitis, septicemia and other infections of the central nervous system are commonly seen in patients with listeriosis. In pregnant women, listeriosis may lead to spontaneous abortion, stillbirth, or fetal death9. In both human and animals, the diseases can be diagnosed based on clinical signs, which can be confirmed by isolating the pathogen from specimens’ characteristic neurological signs10. Moreover, abortion resulted from silage feeding may suggest listeriosis10. In cattle treatment must be administered for a prolonged period of time because recovery may take as long as a month. Listeria monocytogenes susceptible to most treatments include either oxy tetracycline twice daily or penicillin-G (3 to 4 times per day for 7 days)11. As, listeriosis is one of the major emerging food borne diseases in the world and zoonotic infectious disease of humans and animals, this review is aimed at reviewing the current epidemiologic status and public importance of bovine listeriosis.

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