Sources of Enteric Disease in Canada

Abstract

The public is exposed to the risk of enteric infection via foodborne, waterborne, and airborne sources, or via direct contact by infected persons or animals. Food-borne transmission of enteric disease is the most well-known and extensively studied area. Among all foods, meat and poultry products are the largest contributor of foodborne disease outbreaks. Consumption of these products has been linked to enteric infection caused by several important human pathogens such as Escherichia coli O157:H7, Salmonella enterica Typhimurium, S. Enteritidis, Campylobacter species, and viruses. Food animals carry some of these human pathogens with no clinical symptoms. For example, E. coli O157:H7 carried by young cattle, Salmonella and Campylobacter by poultry. Carriage of human pathogens in food animals has serious health implications because it means the farm is a significant reservoir of foodborne illness agents. The ecology of the most frequently occurring human pathogens in the farm environment is reviewed here. Other important vehicles of foodborne gastroenteritis include fruit and vegetables, seafood, and dairy products. Fruit and vegetables, as raw agricultural commodities, are vulnerable to microbial contamination during production, and minimal processing further magnifies the contamination level. The opportunity for fresh produce contamination at production is discussed. Seafood-associated enteric infection is usually the result of environmental contamination and eating raw or undercooked seafood. The frequency of environmental contamination of seafood is examined. Enteric infection due to dairy foods often implicated raw milk, improper pasteurization, and post pasteurization contamination as sources of the problem. Some of the dairy product-associated outbreaks are addressed. Waterborne transmission is a second common route for spreading enteric disease. However when it happens, it usually results in a large number of people being affected. Drinking and recreational waters are two main vehicles. Important waterborne disease agents such as Cryptosporidium, Giardia, Shigella, and E. coli Ol57:H7 are reviewed. Airborne transmission of enteric infection is the least studied area. Airborne microbial contamination and the closely related occupational hazards are acknowledged. Some of the enteric disease agents can be spread through direct contact either by infected animals or humans themselves. Among agents spread by animal contact are verocytotoxigenic E. coli, predominantly E. coli O157:H7, Salmonella species including S. Typhimurium DT104, and Cryptosporidium. Enteric infection by personal contact has been documented for Norwalk virus, hepatitis A, Shigella species, E. coli O157:H7, and Cryptosporidium. The role of direct contact in disease transmission is addressed.KeywordsEnteric DiseaseHemolytic Uremic SyndromeEnteric PathogenEnteric InfectionCryptosporidium OocystThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.