FACTS ABOUT E. coli O157:H7:
Toxin-producing Escherichia coli
Several strains of the bacterium E. coli cause a variety of diseases in humans and animals. E. coli O157:H7 is a type associated with a particularly severe form of human disease E. coli O157:H7 is one of the most virulent (highly infectious) pathogens known to enter the world food supply. It causes diarrhoea, abdominal pain, and in some cases, intestinal bleeding and kidney failure.
The initial symptoms of E. coli O157:H7 illness generally occur within two days after eating contaminated food, though periods of three to five days have been reported. Symptoms increase in intensity during the next 24-48 hours, lasting from four to 10 days. Less than ten E. coli O157:H7 cells may be enough to cause illness in humans. A low infectious dose of two to 2,000 cells has been associated with outbreaks of food borne illness. E coli O157:H7 can survive in acidic environments that are lethal to other pathogens, such as in fermented foods like sausage and apple cider. Though potentially deadly to humans, E. coli O157:H7 is not pathogenic to cattle.
A single cow, or a number of cattle within the same herd, may contain more than one strain of E. coli O157:H7. Some strains are thought to have greater acid tolerance than others.
The source of E. coli O157:H7 contamination on carcasses is likely due to fecal contamination during animal production and slaughter operations. Carcasses may become contaminated during hide removal or by cross-contamination with equipment and workers’ hands. HACCP (food safety control) systems in processing plants cannot eliminate E. coli O157:H7 from foods unless a treatment is added that will kill the pathogen, such as heat pasteurisation or irradiation. Current research shows that competitive exclusion has the potential to eliminate E. coli O157:H7 from cattle before slaughtering. Competitive exclusion involves the use of non-pathogenic micro-organisms to outgrow pathogens in the gastrointestinal tracts of animals.
If swallowed, faecal contaminated water in freshwater swimming areas may cause E. coli O157:H7 infection in both cattle and humans. Fresh manure used to fertilise garden fruits and vegetables may contaminate them with E. coli O157: H7. The largest reported E. coli O157:H7 outbreak, which caused thousands of illnesses, occurred in Japan in 1996. Radish sprouts were implicated as the source of infection.
Though ground beef has been most often associated with E. coli O157:H7 outbreaks in the United States, other implicated foods include raw milk, apple cider, dry-cured salami, lettuce, produce from manure-fertilised gardens, potatoes, radish and alfalfa sprouts, yoghurt, sandwiches, and water.
E. coli O157:H7 causes hemorrhagic colitis, which begins with watery diarrhea and severe abdominal pain and rapidly progresses to passage of bloody stools. It has been associated with HUS, a life-threatening complication of hemorrhagic colitis characterized by acute kidney failure that is particularly serious in young children. E. coli O157:H7 is found in cattle, but there may be other reservoirs; the dynamics of E. coli O157:H7 in food-producing animals are not well understood. Approximately 25,000 cases of foodborne illness can be attributed to E. coli O157:H7 every year, with as many as 100 deaths resulting. E. coli O157:H7 outbreaks have recently been associated with ground beef, raw milk, lettuce, and minimally processed and fresh fruit juices. An outbreak in the fall of 1996 in three western states and British Columbia was associated with unpasteurized apple juice and sickened 66 people, causing the death of one child.