Cambridge University scientists lead battle against chicken bacteria
It's the cause of the most common food-borne bacterial disease in the world - and causes hundreds of thousands to fall ill every year. Now Cambridge scientists are battling the Campylobacter in our chicken meat.
We love our chicken meat. Every day more than two million chickens are consumed in the UK. About 50 per cent of all the meat we eat is poultry – most of it chicken – with consumption nearly doubling over the past 40 years.
While health experts generally agree that chicken meat is more beneficial than red meats such as beef or pork, there is a problem.
About half the chickens sold in the UK and elsewhere carry a bacteria called Campylobacter jejuni, the most common cause of food-borne bacterial disease worldwide.
According to estimates of the government’s Food Standards Agency (FSA) there are more than 280,000 cases of campylobacteriosis in humans each year in the UK. The most common symptoms include diarrhoea, abdominal pain, fever and sometimes vomiting. Children and elderly people are particularly susceptible to infection; it can also lead to post-infection complications and, in some instances, be fatal.
“Campylobacter is a worldwide problem – more and more cases are being reported both in the developed and developing world,” says Dr Andrew Grant at the University of Cambridge.
Dr Grant and his team at the Department of Veterinary Medicine are among those at the forefront of research into the makeup of the bacteria - how it grows, how it is transmitted and how it causes disease.
“It’s a mysterious bacteria we really don’t know a lot about. Some people become sick – others, eating the same chicken, don’t feel any ill effects.”
The UK produces about 880 million chickens, 17 million turkeys, 16 million ducks and a quarter of a million geese each year. It also imports substantial amounts of chickens and chicken meat, mainly from the Netherlands, Thailand and Brazil.
Scientists calculate that globally Campylobacter is responsible for nearly 100 million foodborne illnesses each year and more than 20,000 deaths.
“There’s a complex dynamic involved in the way the bacteria gets into a bird and grow in its gut,” says Dr Grant. “The bacteria are then excreted and, because chickens are coprophagic (they pick up faeces), the bacteria are then reintroduced into the birds.
“Consumption of undercooked poultry, unpasteurized dairy products and contaminated water are the most common causes of infection.”
Campylobacter can be also be transmitted by flies, birds and domestic animals though it’s been found that the gut of a chicken is what’s termed the ideal place for the bacteria to incubate.
Investigating how the bacteria grows in some animals, is transmitted between animals and causes disease in other animals is like a detective exercise: its character has to be established, its various quirks and possible weak points identified and analysed.
The team at the Department of Veterinary Medicine are investigating, among other things, the genes required for Campylobacter to colonise chickens - the ones that promote its transmission and enable its survival in the environment as well as how the bacteria cause disease in humans.
Research is also focused on the way the spiral-shaped bacteria can change and mutate.
“There have been some recent indications that the bacterium is changing,” says Dr Grant.
“It might be moving out of the gut and around the body, infecting the liver and some deep muscle tissues in chickens. That could create serious problems and make the bacteria more difficult to eliminate.”
One of the main points of transmission of Campylobacter is during processing, when the guts of an infected chicken can be spilled and contaminate other carcasses.
New methods of both scalding and chilling to remove bacteria from the surface of the birds are being adopted by some chicken processors.
One of the difficulties of tackling Campylobacter is that several players are involved in bringing a chicken from ‘farm to fork.’
“Everyone has to take responsibility,” says Dr Grant. “The farmer, the processor, the supermarket, food inspectors and consumers all have to play their part in keeping the bacteria under control
“All the links in the chain have to adopt best practice, ensuring bio security and eliminating cross-contamination. At the same time, we need continued research to understand how Campylobacter colonises chickens so that we can devise novel interventions and vaccines, as well as develop an understanding of how it causes disease in humans so that therapeutics can be developed.”
Researchers warn that there is little sign of a silver bullet; a vaccine or some other agent capable of eliminating Campylobacter still seems some way off.
“The good thing is that everyone – the researchers, the farmers, the processors, the supermarkets, the FSA and the consumer bodies – is now working together,” says Dr Grant.
“In the short term we might not be able to do away with the bacteria but at least we can learn to control it in a more comprehensive way.”
How you can stay safe
So how do you – the consumer – control Campylobacter (pronounced cam-pie-lo-bac-ter)? The Food Standards Agency says raw chicken should be stored at 5C or below, and placed at the bottom of the fridge so that no juices can leak and cross-contaminate other foods. When preparing a chicken it should not be washed – water droplets can spread bacteria onto hands, work surfaces, clothing and kitchen equipment. Remember to wash all utensils after handling raw chicken – and wash your hands with soap and warm water. Finally, the chicken should be cooked thoroughly, with no pink meat. And then sit back and enjoy your meal, safe in the knowledge that you’ve killed off Campylobacter and any other bacteria.
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