Strategies for surveillance and prevention

Abstract

Foodborne diseases continue to move newspapers and bowels around the world. A century ago, concern about cholera, typhoid fever, and other enteric diseases led to the sanitary revolution, which controlled these diseases in the industrialised world. Now, newer pathogens have emerged, and they are delivered fresh to our dinner plates by the increasingly centralised and global production of food. Escherichia coli 0157:H7, Cyclospora cayetanensis, caliciviruses, and Salmonella typhimurium DT104 are all part of the growing list of pathogens that may lurk in the stools of the patient with diarrhea, taxing the diagnostic laboratory. E coli O157:H7, a Shiga toxin-producing E coli, is a good example of this new breed of pathogen. Unheard of before 1982, it is now of major concern in Europe, North and South America, and Japan. The toxins cause the illness, which can include renal failure and death. The illness is essentially untreatable, although the organism is susceptible to antibiotics. It has' even been suggested that antibiotic use, which increases toxin production in vitro, could harm the patient. The Organism lives in cattle. Contamination of meat could be reduced by cleaner slaughter practices, as being implemented throughout the USA; even better control will be possible if carefully slaughtered meat is then irradiated. However, illness traced to vegetables contaminated with manure or to direct contact with animals illustrates the need for control at the farm level. The organism finds maize-fed cattle, a specialty of North America, particularly hospitable. New farm-level prevention strategies, such as modification of the bovine diet, might reduce colonisation and thus prevent human disease. The practice of public health is changing as new surveillance strategies develop to detect foodborne pathogens. In the USA, an active surveillance system called FoodNet tracks the frequency of specific infections, to better determine their sources and the burden they pose (figure). A molecular subtyping network called PulseNet now permits DNA “fingerprints” of strains tested in many different locations to be compared rapidly over the internet, and identifies potential links that would not otherwise have been suspected. A similar method is under development in Japan. In Europe, EnterNet combines surveillance information across countries, so that international events can be identified and investigated more quickly. With these new tools, epidemiologists and microbiologists can identify Sources of infection and guide prevention strategies more precisely than ever. Increasing antibiotic resistance is another challenge. The impact of antibiotics used in agriculture on public health is being felt as resistant organisms flow into the food supply. The spread of multi-resistant Campylobacter and Salmonella has veterinarians and physicians reaching for similar powerful antimicrobial agents to treat infections, and highlights the need for policies for prudent use and better infection-control strategies in animal management. Growing consumer demand for foods produced using as little antibiotic as possible will propel the argument rapidly to its obvious conclusion: antibiotics are not a substitute for better on-farm infection control. The same consumers who are educated on how to cook their meat and eggs, wash their hands, and choose restaurants with reasonable health-inspection scores, expect food coming into their homes to be safer. Increasingly, the safety of that food depends on what the animals consume. Making the animals, feed free of pathogens, disinfecting their drinking water, properly treating the manure they produce, and isolating the contagiously ill are all part of the coming sanitary revolution on the farm. New prevention technologies, including probiotics fed to young animals to prevent Salmonella colonisation, electron-beam and gamma-source irradiation, and in-shell egg pasteurisation, are available or imminent. Controls that make food safer can be built in wherever the food comes from, if consumers, their physicians, and the public health community insist on foods that have been processed for safety.