Listeriosis--history and actual developments.

Although apparently observed before, the history of listeriosis dates back approximately 60 years. First known as a cause of epidemics and sporadic cases in some 50 species of animals, the disease appears now with increased frequency among human populations at risk. The causative agent Listeria monocytogenes is primarily a psychrophilic soil-borne bacterium with a wide pathogenic potential thus provoking primarily septicemia, meningitis and intrauterine infections. Recent observations indicate certain types of food being the principle vehicle for transmission of human listeriosis. This would parallel the epizootic situation in domestic animals. Further studies of the mechanisms leading to clinical and subclinical infections are just as necessary as reliable methods to determine the immunity status of individuals at risk.