Livestock are the number 1 source of food poisoning bug
A new study has discovered that 97 percent of campylobacteriosis cases (the main form of food poisoning in the developed world) were caused by bacteria typically found in animals farmed for meat and poultry – overturning previous thinking that animals farmed for meat are not an important carrier of the human disease.
The results suggest that the primary source of infection to humans is through the food chain and could be dramatically reduced by better farm practices and hygiene.
The DEFRA funded work, which appears in the Sept. 26, 2008, issue of PLoS Genetics, is based on DNA-sequence comparison of thousands of bacteria collected from human patients and animal carriers and was carried out by Lancaster University, The University of Liverpool’s National Centre for Zoonosis Research and the Health Protection Agency.
Campylobacter jejuni causes more cases of gastroenteritis in the developed world than any other bacterial pathogen, including E. coli, Salmonella, Clostridium and Listeria combined. Wild and domestic animals act as natural reservoirs for the disease, which can also survive in water and soil. However, the relative importance of these sources is unclear, and recent work has suggested that livestock are not the main reservoir for human disease.
Researchers led by Daniel Wilson at Lancaster University and supported by the HPA Regional Laboratory in Manchester, the laboratory at the Royal Preston Hospital and the HPA’s Cumbria and Lancashire Health Protection Unit sequenced the DNA of bacteria collected from 1,231 patients and compared it to Campylobacter jejuni DNA sequences collected from wild and domestic animals, and the environment. They used evolutionary modelling to trace the ancestry of human C. jejuni back to one of seven source populations.
In 57 percent of cases, the bacteria could be traced to chicken, and in 35 percent to cattle. Wild animal and environmental sources were accountable for just three percent of the disease.
Their results have clear implications for public health policy. “The dual observations that livestock are a frequent source of human disease 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.
Further studies are underway in the US, UK and New Zealand and the researchers hope the current study will add impetus to initiatives aimed at controlling food-borne pathogens.