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Listeriosis is a severe disease caused by bacteria of the genus Listeria. Human listeriosis is almost exclusively caused by the species Listeria monocytogenes, although L. ivanovii cause a significant proportion of listeriosis in domestic animals.

Consumption of contaminated food and feed is the main route of infection by Listeria spp. in humans and animals respectively, although human infection can also result from direct contact with infected animals. Transmission to the foetus/neonate can occur in the case of pregnancy-associated cases. Flu-like symptoms to severe life-threatening meningitis and septicaemia are characteristic of listeriosis, with mortality rates as high as 40% reported. Vulnerable groups such as neonates, the elderly, immunocompromised, or pregnant women are susceptible to more serious forms of the disease. An infection during pregnancy can result in premature delivery, intrauterine death, as well as septicaemia or meningitis in the newborn. A milder, less invasive form of listeriosis, characterised by gastroenteritis and fever, has also been described, occurring mainly in healthy individuals exposed to a significant amount of L. monocytogenes. Cutaneous or ocular listeriosis can also occur, usually after contact with infected animals.

Despite the relatively low number of cases reported each year in Ireland, infection by L. monocytogenes is considered a serious threat to public health due to its ubiquitous nature, relatively high mortality rate and ability to multiply at refrigeration temperatures.

View our factsheet on Listeria Monocytogenes