Chicken has been confirmed as the source of most Campylobacter infections, according to a research report published by the Food Standards Agency (FSA) in the United Kingdom.

The aim was to estimate contributions of the main sources to human infection and to identify changes over time. The work by Oxford University also looked at antimicrobial resistance.

about 300,000 cases of Campylobacter infections are estimated to be acquired from food each year in the United Kingdom and it costs the UK about £1 billion ($1.4 billion) annually.

The project assessed patient samples between October 2015 and September 2018 from a representative urban site in North Tyneside and a rural one in Oxfordshire alongside foods sampled from retail in York, Salisbury and London.

Past work has found Campylobacter types in fresh chicken often match those from ill people in Sweden and poultry meat is a major source of infection in New Zealand.

Role of lamb’s liver
The UK Campylobacter Source Attribution study estimated that 70 percent of Campylobacter jejuni and just under 50 percent of Campylobacter coli infection was linked to chicken as the source. These figures were relatively stable over time.

Ruminants such as sheep were the second most common source for Campylobacter jejuni and the main one for Campylobacter coli while there was some link to pigs. Findings on lamb’s liver consumption show it could cause several thousand cases in England each year.

A total of 3,821 of 6,119 patients returned a completed questionnaire. Reported duration of illness lasted up to 182 days. Almost 600 people were admitted to hospitals for 1 to 42 days.

Overall, 2,725 respondents reported eating chicken in the five days prior to onset of symptoms. This was followed by duck, turkey or goose and liver pate or parfait. Consumption of unpasteurised, raw milk was reported by 67 people and any cold milk by 1,066 people.

Nearly two thirds of people ate out in the five days before symptoms and close to one in five reported travel abroad. The top countries were Spain, India, Portugal, France and Turkey.

Product testing results
Sampling of fresh raw chilled food from retailers in three places from January 2017 to 2019 found Campylobacter in a quarter of tests. It included 1,890 samples of duck meat and liver, ox, calf and lamb livers and turkey.

Campylobacter was detected in 25.8 percent of samples and 1.4 percent had counts above 1,000 colony forming units (cfu) per gram. The highest single count was 57,000 cfu/g in lamb’s liver.

The proportion of turkey meat samples contaminated was significantly lower than other types. Duck liver and duck meat were more likely to be contaminated compared with ruminant liver samples. Campylobacter Lari was detected in one duck liver sample.

Rick Mumford, FSA head of science, evidence and research, said: “We will use these findings to better understand the causes of Campylobacter infection, and to inform further work on foodborne transmission. This will also help to identify further research areas to explore as we seek to reduce the overall burden of Campylobacter infection in the UK.”

For Campylobacter coli, most isolates had no closely genetically related isolate in the study, and, wher identified, clusters were very small with four or fewer. However, for Campylobacter jejuni, 54 percent of isolates were part of clusters ranging from small to very large at 116 isolates. This substantial clustering suggests shared sources or transmission for isolates within clusters that could be targets for investigation and intervention, according to the report.

The study also revealed an increase in antimicrobial resistance in Campylobacter strains between 1997 and 2018.

There was a rise in fluoroquinolone and tetracycline resistance in Campylobacter jejuni human isolates. Fluoroquinolone resistance was more frequent in Campylobacter jejuni isolates from chicken than other animals, whilst tetracycline resistance was more common in poultry and pig isolates than ruminants. Resistance to macrolides and aminoglycosides remained low.