Scientists have revealed how genes influence chickens’ resistance to Campylobacter.

Their study, published in the Scientific Reports journal, also identified that when designing control strategies for the bacteria non-genetic factors should be taken into account.

Researchers from the Royal Veterinary College, Roslin Institute, and poultry breeding company Aviagen investigated the genetic make-up of 3,000 chickens bred for meat, also called broilers.

They looked at whether parts of their genetic code were associated with resistance to Campylobacter colonization. This was done by looking for variation in the chickens’ genome and the association with numbers of Campylobacter in the gut of the birds. The team combined this with analyses of the expression of genes in chickens that were resistant or susceptible to colonization by the bacteria.

Control strategies
Campylobacter is the leading cause of bacterial foodborne illness worldwide. Handling or consuming contaminated poultry meat is a key risk factor for campylobacteriosis.

A potential control strategy is to selec poultry with increased resistance to Campylobacter due to a lack of effective vaccines and treatments for pre-slaughter control.

Professor Mark Stevens, from the Roslin Institute, said the research looked for regions of the chicken genome associated with resistance to the bacterium.

“Our data indicates that there is low genetic basis for resistance to Campylobacter colonization and also show that non-genetic factors play a more significant role in carriage of Campylobacter in chickens. In addition, the regions of the genome associated to resistance to colonization were highly prevalent in the chicken line studied.”

All chickens were naturally exposed to Campylobacter present in their environment, which mimics how they are exposed on a commercial farm.

Other factors that play a part
The study found that although there are genetic factors that influence Campylobacter colonization, they play a minor role, so the impact of non-genetic and environmental factors need to be better understood to reduce Campylobacter levels in poultry.

Researchers assumed a uniform exposure of birds to Campylobacter during 16 months of sampling. Males had a higher Campylobacter load than females, levels showed seasonal variability, with date of sampling having a significant impact while body weight did not have a significant effect.

Other non-genetic factors that may explain the variation in Campylobacter colonization include strain variation, time and level of exposure relative to sampling, coinfections, variation in gut microbiota, and diet and feed intake.

Dr. Androniki Psifidi, lecturer in veterinary clinical genetics at the RVC, said other non-genetic factors will need to be considered in the design of control strategies.

“Although we identified a genetic component to resistance of chickens to Campylobacter, this was relatively small, and the majority of the chickens we studied already carried regions of the genome associated with resistance to gut colonization.”

The study received funding from Aviagen, Scottish Government and the Biotechnology and Biological Sciences Research Council, as part of UK Research and Innovation.