Contrary to popular belief, the foodborne pathogen Campylobacter jejuni is not a harmless commensal bacteria in chickens but can cause disease in some breeds of poultry, according to research published in mBio, the online open-access journal of the American Society for Microbiology.
"The main implication is that campylobacter is not always harmless to chickens. This rather changes our view of the biology of this nasty little bug," said study author Paul Wigley of the Institute for Infection & Global Health at the University of Liverpool in the U.K.
C. jejuni is the most frequent cause of foodborne bacterial gastroenteritis in the world and the Centers for Disease Control & Prevention estimate that it affects approximately 1.3 million people per year in the U.S. Chicken is the most common source of infections. Infection of chickens had previously not been considered to cause disease and the bacteria were thought to be part of the normal microbiota of the birds.
In the study, Wigley and his colleagues experimentally infected birds from four commercial breeds of broiler chickens. They found that while levels of the bacteria in the intestines did not differ by breed, immune response and inflammation did, to the extent that one breed showed damage to the gut mucosa and developed diarrhea.
"Interestingly, the breeds did not differ in the levels of bacteria we found in their intestines after infection, even when kept to normal slaughter age," Wigley said. "This suggests that chicken breed has little direct effect on the risk of campylobacter entering the food chain but has a big effect on the health of the birds."
The most important finding, Wigley said, is that campylobacter infection directly affects broiler chicken health and welfare. The U.S. produces more than 8 billion broiler chickens per year and the U.K. produces nearly 1 billion.
"On the positive side, we now know that chickens produce a robust immune response to infection, which, in the longer term, may allow us to develop vaccines," Wigley said.
The research was funded by the U.K.'s Biotechnology & Biological Sciences Research Council as well as a consortium of poultry producers, breeders and retailers.