Livestock Are the Main Source of Food Poisoning, Study Shows

By Chantal Britt

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Sept. 26 (Bloomberg) -- Animals farmed for meat and poultry are the principle source of food poisoning in humans, according to new research published in PLoS Genetics.

Using a new method of evolution-based gene-typing, a group of U.K. and U.S. researchers found that 97 percent of the infections reviewed came through the food chain, from chicken, cattle and sheep. Previous studies had shown that the majority of cases were caused by wild animals or environmental sources.

Campylobacter jejuni causes more cases of gastro-enteritis in the developed world than any other bacteria, including E. coli, Salmonella, Clostridium and Listeria combined. The spread of the disease may be cut by improving food hygiene during preparation and by enforcing on-farm security measures, said Daniel Wilson of the University of Chicago, who led the research.

``The dual observations that livestock are a frequent source of human disease isolates, and that wild animals and the environment are not, strongly support the notion that preparation or consumption of infected meat and poultry is the dominant transmission route,'' Wilson said.

Past research found that campylobacter in humans most closely resembles non-livestock strains and that some outbreaks may have been due to contaminated water, suggesting that livestock weren't the main source for human disease.

Evolutionary Modeling

The researchers from Chicago, Illinois, and Lancashire in England collected bacteria from 1,231 patients as well as from wild and domestic animals, and the environment. They compared the genetic sequences of the samples, using evolutionary modeling to trace the human bacteria back to its source.

Wilson and his team found that the vast majority were caused by the spiral-shaped bacteria typically found in chicken and livestock. The results may spur more initiatives aimed at controlling food-borne pathogens, Wilson said.

Measures may include disinfecting farm premises and water supplies, restricting access to livestock to essential personnel, minimizing the use of invasive practices such as thinning in chickens, securing premises from wild birds and mammals, and protecting food supplies from bacterial contamination, Wilson said.

Just one drop of juice from raw chicken meat can infect a person. One way to become infected is to cut poultry meat on a cutting board, and then using the unwashed cutting board or utensil to prepare vegetables or other lightly cooked food. Most of the 2.4 million Americans who develop gastro-enteritis each year become ill with campylobacteriosis from eating raw or undercooked poultry meat.

The disease -- with symptoms including diarrhea, cramping, abdominal pain, nausea and fever -- may last as many as 10 days and costs the U.S. economy more than $4 billion, Wilson said. Most cases occur as isolated, sporadic events, not as part of an outbreak, according to the U.S. Centers for Disease Control and Prevention.


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