THE secret of how to beat a deadly food poisoning bug may lie in Scotland's farmyards. Scientists have found that up to a fifth of Scottish farmers are immune to infection with E coli.
Researchers conducting tests on farmers in the Grampian region found that one in five showed signs of immunity to the naturally-occurring organism, which is spread mainly through cattle dung.
The findings suggest that repeated exposure to the bug has given farmers protection and may help in the search for a vaccine against the condition. More than 20 people died in Scotland in the world's worst outbreak of fatal E coli 0157 in 1996, when a batch of meat sold by a butcher in Lanarkshire was contaminated.
Researchers hope that a vaccine will protect at-risk groups, such as food industry workers and those working with children. The elderly and young children - whose natural immune systems are not as strong - are most susceptible to the disease.
In the study, conducted by scientists from Bangor University in Wales, around 200 farmers in Grampian and North Wales have so far been tested.
Researcher Dr Prysor Williams said: "We are taking small samples of blood and saliva and looking for antibodies in the samples. That will tell us if that individual has been exposed to 0157. If antibodies are present it shows that that individual has a degree of immunity because all the volunteers are not patients."
In a previous study of farmers in England and Wales, the researchers found that around three per cent had immunity to E coli 0157.
But in the Grampian region - thought to have one of the highest rates of the infection in the world - results have so far suggested a much higher rate of antibodies.
"We are finding about a fifth (20 per cent) of farmers do have some degree of immunity," Williams said.
Rates of E coli 0157 in Scotland are higher than the rest of the UK. Last year, there were 4.6 cases per 100,000 people in Scotland, compared with fewer than two per 100,000 in England. In Grampian there were 11.1 cases per 100,000. The illness causes severe stomach upsets but can also lead on to fatal complications.
The reasons for the higher rates in Scotland remain unclear. Cattle are the main sources of the organism, although it rarely causes illness in animals. Infection in humans can happen when they ingest the organisms, originating from animal faeces, through contact with grazing animals or contaminated water supplies. Outbreaks of E coli 0157 have occurred after visits to farms, petting zoos and agricultural shows.
Williams said the work at Bangor should help other scientists in their search for such a vaccine, as it appeared that some low level of exposure helped people build up immunity.
Epidemiologists, who study the spread of disease, said a vaccine would be a welcome step forward.Dr John Cowden, a consultant with Health Protection Scotland, said: "If there was a cheap, effective and free-of-side-effects vaccine against a disease that is very severe, it would be a good thing,"
Farmers' leaders said they were not surprised that so many farmers seemed to be immune to the disease despite working in a high-risk environment.
Rob Livesey, livestock committee chairman for the National Farmers' Union Scotland and a livestock farmer in Selkirk, said: "We probably have some resistance to it or don't know it is there. But when you get visitors on the farm you make sure they are as well protected against any risks as they can be."
From a practical point of view it was difficult for farmers to eradicate the risk to themselves posed by E.coli, he added, but he had never known any farmers become ill with the infection.
"I have never heard of any farmers having any problems. It is people who come onto the farm who might have a problem. It is catastrophic when it happens but it is not common."