Surveillance of listeriosis and its causative pathogen, Listeria monocytogenes

To manage the problem of foodborne listeriosis requires an understanding of the burden of the disease on a worldwide scale as foods that are prone to contamination are eaten widely domestically and many are traded globally. Surveillance of the disease, caused by Listeria monocytogenes, is typically restricted to developed countries, but many of these do not consider listeriosis as a notifiable disease and estimate the numbers by other means. Incidence rates range from 0.3 to 1.3 per 100,000, but most are in the 0.3–0.5 range, irrespective of the regulatory system and industry control programmes that have been in place. Ready-to-eat foods are the vehicle for transmission of the Listeria through contamination somewhere in the food chain. Meat, poultry and dairy products have been most frequently implicated, but other foods including produce may also have been vehicles of transmission. Large outbreaks are usually linked to errors in food processing plants, such as contaminated slicing machines, followed by opportunities for growth of the pathogen. Less is known about home-generated illnesses but incorrect use of refrigerators can allow cross-contamination and growth of the pathogen to levels that can cause infections. In the U.S., door-to-door salesmen have sold contaminated Hispanic soft cheeses that have led to outbreaks and stillbirths. In addition to outbreak investigation, case-control studies, and the use of experts, risk assessments, and food attribution studies can help focus on areas of greatest risk for prevention and control measures throughout the food chain.