23 April 2013

5 minute read

About E.coli O157 and the Study

E.coli O157 is a serious gastrointestinal pathogen which can be transmitted from cattle faeces to humans via the environment or through the food chain, writes the Food Standards Agency.

A literature review identified three control strategies which had been shown to reduce the prevalence and/or shedding of E.coli O157 by infected cattle:

• the use of probiotics in feed
• the vaccination of animals
• measures for improving biosecurity on farms

Analyses compared the costs of implementing each as a control strategy against the public health benefit. The results suggested that, at a national level, the use of vaccines or probiotics could be cost effective.

Both of these approaches have shown promise in research carried out in the US. However, little work has been undertaken to establish how feasible it would be to implement these methods in UK farming systems, and how effective they could be in reducing the public health risk associated with E.coli O157 in this country.

Talking to Farmers

A survey of around 500 UK farmers indicated that there are high levels of awareness of the risks of E.coli O157 to public health, and recognition that they have a responsibility to address the issue.

Despite this, many are not convinced of the benefits of investing in treatments such as vaccines and probiotics. However, the responses suggested that improved access to information and evidence for the safety and effectiveness of controls would encourage farmers to take action.

Farmers who opened their premises to the public were more likely to be willing to pay or to spend time in controlling E.coli O157, and the findings suggested that targeted vaccination to open farms could be a viable option for reducing human exposure to the pathogen.

Further Research

This study has been an important first step in identifying methods with the potential to manage the spread of E. coli O157 on UK farms.

It makes recommendations on how farmers could be incentivised to implement control measures and highlights the need for further research to strengthen the evidence base on how on-farm interventions could benefit public health.

The Agency aims to publish its requirements for research, to address some of these recommendations, in March 2013.

Background to the Study

Co-funded by the Department of Environment, Food and Rural Affairs (Defra), this study was undertaken by the Scottish Agricultural College (now Scotland's Rural College; SRUC) in collaboration with the University of Glasgow.

It addresses a recommendation made in the report of the Public Inquiry into the foodborne outbreak of E.coli O157 which occurred in South Wales in 2005. See the link below for more information about this and to access the full study.

Science Behind the Story

E.coli O157 is a verocytotoxin producing pathogen belonging to a group of bacteria called Enterohaemorrhagic E.coli (EHEC). These can cause mild to severe illness, characterised by abdominal cramps, vomiting and bloody diarrhoea.

EHEC infections can also lead to the serious conditions haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopaenic purpura (TTP). These conditions affect the blood, kidneys and, in severe cases, the central nervous system - and can even lead to death. In the UK, EHEC infections are most commonly attributed to E.coli O157, for which there were over 1,000 cases reported in 2010 and 2011.

The main source for EHEC is the gut of ruminant animals, particularly cattle, which excrete or shed the bacteria in their faeces. Some cattle excrete EHEC at significantly higher levels than other animals in the herd; a phenomenon known as 'supershedding'. Humans can become infected through direct exposure to faeces in the environment or when faecal contamination enters the water supply or food chain.

Results and Findings

• A literature review on the efficacy of control measures for reducing E. coli O157 shedding in livestock identified a total of 221 relevant scientific publications dating from 1990 to 2011. It was noted that the majority of peer-reviewed work on this subject was dominated by publications from North America.
• From these publications, three control strategies were identified for which there was sufficient quantitative data on their ability to reduce shedding levels and/or the prevalence of infected cattle, to allow models to be developed to undertake cost-benefit analyses. These were:
• the use of probiotics in feed
• the vaccination of animals
• a combined package of eight biosecurity measures.
• The results suggested that using vaccines or probiotics to control E. coli O157 could, in some circumstances, payback the costs. However, this outcome is heavily dependent on the preventable human losses, especially the severity of human illnesses, and not just the number of cases prevented.
• The views of UK farmers on adopting measures for controlling E. coli O157 in cattle were also examined. This was done via a telephone survey of 405 cattle farmers and an online survey of 91 farmers who deliberately open their farms to the public. The findings of the survey suggested that increasing all farmers’ access to information would help to improve levels of awareness and change attitudes with regard to the adoption of on-farm controls for E. coli O157.
• Both vaccines and probiotics have shown promise in North American studies. However, the findings from the survey of farmers showed that although there is an awareness of the human health risks associated with E. coli O157, and recognition that farmers have a responsibility to address the issue, the benefits are not currently obvious, and there is a reluctance to adopt any control measures that are not known to be efficacious and safe. The authors also highlighted the lack of incentives for farmers to adopt controls; given the fact that E. coli O157 does not cause disease in livestock.
• Further engagement with relevant stakeholder groups indicated that the open-farm sector was interested in exploring the use of vaccines. However, it was concluded that demand for the application of on-farm controls for E. coli O157 by beef and dairy farmers in the UK would likely to be limited in the absence of clear evidence that such measures would be effective in protecting public health.
• The report makes a number of recommendations for future work needed to drive the uptake of on-farm interventions and research to strengthen the evidence base for the efficacy of controls in reducing shedding in UK farming systems and the subsequent benefits to human health. The FSA is planning to publish its requirements for research to address these recommendations later in 2013.

March 2013