Medical Matters: Were you unlucky enough to develop gastroenteritis over the festive period? If you did, there are indications that one particular bug is on the increase and may have been the source of your illness, writes Dr Muiris Houston.
Campylobacter jejuni may not have the same name recognition as salmonella, but infections by the bacterium appear to be rising. In the Eastern Regional Health Authority area last year, more than 500 cases of the stomach bug were detected, a significant increase over previous years.
The rise has prompted both the authority and the National Disease Surveillance Centre to undertake further research into the risk factors for campylobacterosis (the medical name for infections with campylobacter).
C. jejuni - a reference to the jejunum, part of the small intestine - is a subtype of the campylobacter family. The most important from a human-disease perspective, it is now the most frequent cause of bacterial, as distinct from viral, gastroenteritis. C. jejuni is found in the gut of many animals and birds. Chickens are a particular source; one US food study found campylobacter in 42 per cent of chickens purchased across the country. Salmonella was found in 12 per cent. Both bacteria were present in 5 per cent.
In Switzerland, 40 per cent of campylobacter samples isolated from chickens are resistant to at least one antibiotic, a reflection of the increased use of antibiotics in the farming of poultry. And unlike most people who develop gastroenteritis as a result of the bug - and who make a good recovery without the help of antibiotics - patients need medication if there is a threat of infection spreading to the blood.
Eating unwashed or undercooked chicken is the leading cause of campylobacterosis. Studies have shown a correlation between handling and consuming chicken; barbecues present a special hazard because they allow easy transmission of the bacteria from raw meat to hands and other foods.
It can take up to seven days after the bug enters the intestine before a person becomes sick. A high temperature, bloody diarrhoea, abdominal pain and flu-like symptoms are the result. Although these symptoms are also features of other bacterial infections of the gut, the intensity of abdominal cramp and pain is worse with campylobacter. Almost all cases resolve within a week, although the patient will continue to excrete the organism in faeces for several weeks.
About one in 1,000 people, however, goes on to develop a neurological condition called Guillain-Barré syndrome, resulting in temporary paralysis. Dr Stewart Thompson, a microbiologist at the Medical College of Georgia, in Augusta, and an expert on how campylobacter infection can make people sick, says that most of these infections run their course and leave the patients fine.
"But weeks later, some patients with certain strains of the bacteria develop Guillain-Barré syndrome. What appears to be happening in those patients is there are sugars on the outside of the bacterium that resemble sugars on peripheral nerve cells. So the body detects this infection, mounts an immune response against it but inadvertently generates an autoimmune response against the body's own peripheral nerve cells."
The neurological syndrome is named after two Parisian doctors, Georges Guillain and Jean Barré, who in 1916 described the cases of two soldiers who had a fever complicated by an ascending paralysis of the muscles of the legs. The disease reached its peak in a few days and was followed by a slow but ultimately complete recovery. When spinal fluid is removed from patients with the syndrome it is found to contain much higher levels of protein than normal.
In mild cases there is little disability, but in 20 per cent of people with Guillain-Barré the respiratory muscles are affected. They may require artificial ventilation until the paralysis passes away. Even in these severe and frightening cases recovery is usually complete, although a small minority of patients are left with a residual disability.
Dr Thompson and other scientists are looking for proteins on the surface of the bacteria to use as the basis for a vaccine to immunise people against campylobacter. Repeated infection means that children in Thailand develop immunity to all local strains of the bug by the time they start school. So, in theory at least, an effective vaccine looks possible.
In the meantime, take care cooking poultry. Otherwise, you might get more than a nasty dose of gastroenteritis.
You can e-mail Dr Muiris Houston at mhouston@irish-times.ie. He regrets he cannot answer individual queries