Tracing Campylobacteriosis Back to Meat Animals

UK - A recent study that sourced campylobacteriosis of over a thousand patients found that almost all of them were caused by bacteria from animals farmed for meat.

29 September 2008

3 minute read

Europe

Researchers from the US and the UK sequenced the DNA of bacteria collected from 1,231 patients in Lancashire, England and compared it to Campylobacter jejuni DNA sequences collected from wild and domestic animals and the environment.

C. jejuni causes more cases of gastroenteritis in the developed world than any other bacterial pathogen, including E. coli, Salmonella, Clostridium and Listeria combined, claims the study.

C. jejuni is the leading cause of bacterial gastro-enteritis in the developed world. It is thought to infect 2–3 million people a year in the US alone, at a cost to the economy in excess of US$4 billion.

C. jejuni is a widespread zoonotic pathogen that is carried by animals farmed for meat and poultry. A connection with contaminated food is recognized, but C. jejuni is also commonly found in wild animals and water sources. Phylogenetic studies have suggested that genotypes pathogenic to humans bear greatest resemblance to non-livestock isolates.

Moreover, seasonal variation in campylobacteriosis bears the hallmarks of water-borne disease, and certain outbreaks have been attributed to contamination of drinking water. As a result, the relative importance of these reservoirs to human disease is controversial.

The study used multilocus sequence typing to genotype 1,231 cases of C. jejuni isolated from patients in Lancashire, England. By modeling the DNA sequence evolution and zoonotic transmission of C. jejuni between host species and the environment, they were able to assign human cases probabilistically to source populations.

This population genetics approach reveals that the vast majority (97%) of sporadic disease can be attributed to animals farmed for meat and poultry. Chicken and cattle are the principal sources of C. jejuni pathogenic to humans, whereas wild animal and environmental sources are responsible for just 3% of disease.

The results imply that the primary transmission route is through the food chain, and suggest that incidence could be dramatically reduced by enhanced on-farm biosecurity or preventing food-borne transmission.