Vaccinating cattle against the E. coli O157 bacterium could cut the number of human cases of the disease by 85 percent, according to scientists who have examined the disease's transmission to humans.

The bacteria, which cause severe gastrointestinal illness and even death in humans, are spread by consuming contaminated food and water, or by contact with livestock faeces in the environment. In Scotland alone, there are an average of 235 confirmed cases of the disease each year. Cattle are thought to be the main reservoir for the bacterium.

Although vaccines for cattle do exist, these are rarely used.  However, recent research into the disease's transmission by a team of scientists from institutions all over Scotland has discovered that vaccinating cattle could lead to a major reduction in cases.    

The research was conducted by scientists from the Universities of Glasgow and Edinburgh, the Royal Veterinary College, Scotland's Rural College (SRUC) and Health Protection, working in collaboration. Researchers used veterinary, human and molecular data to examine the risks of E. coli O157 transmission from cattle to humans, and to estimate the impact of vaccinating cattle.

The risk of E. coli O157 infection is particularly significant when the cattle are 'super-shedding' – excreting extremely high numbers of bacteria in their faeces for a limited period of time. Vaccines against the bacteria exist that can reduce super-shedding. The researchers worked out that, as a result, vaccinating cattle could reduce human cases by nearly 85 percent, far higher than the 50 percent predicted by previous studies. The team said this was because earlier investigations simply looked at the efficacy of current vaccines in cattle.

They recommend the livestock industry roll out use of vaccines in light of their findings. The collaborative group has remained together to continue its research, with the aim of developing even more effective vaccines.

Lead author, Dr Louise Matthews, Senior Research Fellow in the Institute of Biodiversity, Animal Health and Comparative Medicine, said, "E. coli O157 is a serious gastrointestinal illness. The economic impact is also serious – for instance studies in the US suggest that healthcare, lost productivity and food product recalls due to E. coli O157 can cost hundreds of millions of dollars each year.

"Treating cattle in order to reduce the number of human cases certainly makes sense from a human health perspective and, while more work is needed to calculate the cost of a vaccination programme, the public health justification must be taken seriously."

However, controversies over the use of medicines in animal agriculture have limited the take up of vaccines. Under US law, one version of the vaccine cannot be fully licensed because medicines for veterinary use must show that animal health is improved. As E. coli O157 does not harm cattle, the vaccine cannot be shown to improve animal health.

The researchers from Scotland said that, in such cases, more moves must be made to assess the impact of treatment involves coordination between human and veterinary health practitioners. This 'One Health' approach is gradually gaining ground, and has appeared in some recent public policies.

Senior author Professor Stuart Reid of the Royal Veterinary College commented, "We increasingly recognise the fact that we share a common environment with the animals we keep – and inevitably the pathogens they harbour. This study is an excellent example the interface between veterinary and human medicine and of the concept of 'One Health' in action – controlling infections in animals can have a major impact on public health."