Campylobacter: five key trends in food poisoning cases
Gordon Nicholls, a member of the Health Protection Agency, now part of of Public Health England, currently on secondment at the European Centre for Disease Prevention and Control in Stockholm, reflected on more than 1M confirmed cases of campylobacter over the past 20 years.
According to figures from the Food Standards Agency (FSA), the pathogen was responsible for more than 371,000 cases of food poisoning in England and Wales in 2009 and accounts for a third of the cost of the burden of foodborne illnesses.
It is found mainly in poultry but also in red meat, unpasteurised milk and untreated water, with Nicholls citing research which showed that consumption of infected chicken was responsible for about 41% of cases. FSA figures suggest it could be as high as between 60% and 70%.
The five trends Nicholls identified were:
- A long-term change over the period resulting in a surge in cases over the past few years.
- Clear seasonal increases in the number of cases in the spring.
- A marked increase in cases among those over 50 years of age.
- A greater number of cases in rural areas.
- More cases among the affluent cases than the deprived.
Difficult to analyse
Nicholls said there were no simple answers to explain the underlying key trends for the outbreak of the disease. That was not least because, in most cases, fewer than 10 people were affected, making it “very difficult” to analyse.
However, he did provide a number of possible contributory factors.
In relation to the long-term change that has seen the number of cases spike in recent years, he said that could be attributed to longer life expectancy, especially for men, who record a higher number of campylobacter cases than women.
Furthermore, greater awareness of the causes and effects among GPs and healthcare professionals “may be leading to more cases being recorded”. But, overall, he “suspected the rise was down to more exposure” to campylobacter, particularly through infected chicken.
One factor to consider for the surge in cases among the over-50s, he added, was the increasing use of medication that reduces stomach acid. These are “most commonly used later in life” and “increase susceptibility to gastrointestinal infections,” he said.
Increase in campylobacter
Several studies have shown there were repeated increases in the number of campylobacter cases in the spring, with the largest rise among newborn to nine year-olds. Nicholls said there “was lots of dispute about what was causing this”, but said the undercooking of barbecued or grilled meat at this time of the year could “explain some of the seasonality”.
Other possibilities were closely linked to the factors associated with another of the key trends – the fact that there are more rural cases than urban outbreaks.
These included the possibility of transmission from cattle to chicken by flies and the potential transmission from faeces or raw meat to ready-to-eat food, also by flies.
Finally, Nicholls suggested higher levels of access to healthcare and more frequent foreign travel could explain why there appeared to be more cases among the affluent classes.
“Around 18% of cases in England and Wales can be attributed to travel overseas,” he told delegates at the event in central London this week.
Research should focus on the reasons for these key trends, said Nicholls.
Also, action was needed to reduce chicken contamination in production and to study what he termed as the possible “systematic” infection of chickens with campylobacter. Recent outbreaks caused by the consumption of chicken liver and chicken liver pate made that even more important, he added.
