Bacterial food-borne zoonoses

In many countries of the world, bacterial food-borne zoonotic infections are the most common cause of human intestinal disease. Salmonella and Campylobacter account for over 90% of all reported cases of bacteria-related food poisoning world-wide. Poultry and poultry products have been incriminated in the majority of traceable food-borne illnesses caused by these bacteria, although all domestic livestock are reservoirs of infection. In contrast to the enzootic nature of most Salmonella and Campylobacter infections, Salmonella Enteritidis caused a pandemic in both poultry and humans during the latter half of the 20th Century. Salmonella Typhimurium and Campylobacter appear to be more ubiquitous in the environment, colonising a greater variety of hosts and environmental niches. Verocytotoxin-producing Escherichia coli O157 (VTEC O157) also emerged as a major food-borne zoonotic pathogen in the 1980s and 1990s. Although infection is relatively rare in humans, clinical disease is often severe, with a significant mortality rate among the young and elderly. The epidemiology of VTEC O157 is poorly understood, although ruminants, especially cattle and sheep, appear to he the major source of infection. The dissemination of S. Enteritidis along the food chain is fairly well understood, and control programmes have been developed to target key areas of poultry meat and egg production. Recent evidence indicates that these control programmes have been associated with an overall reduction of S. Enteritidis along the food chain. Unfortunately, existing controls do not appear to reduce the levels of Campylobacter and VTEC O157 infections. Future control strategies need to consider variations in the epidemiologies of food-borne zoonotic infections, and apply a quantitative risk analysis approach to ensure that the most cost-effective programmes are developed.