Tackling enterohaemorrhagic E coli at source
THERE is a need to better understand the epidemiology of enterohaemorrhagic Escherichia coli (EHEC) in cattle, people and environmental reservoirs in order both to improve knowledge and develop strategies for tackling these pathogens at source.
This is among the conclusions drawn in a report published by the Food Standards Agency (FSA) in Scotland recently, which was based on a workshop held at Easter Bush near Edinburgh in November last year. The workshop, which was hosted by the FSA in Scotland in conjunction with the Knowledge Transfer Network Biosciences and the University of Edinburgh, brought together participants from around the world to discuss current knowledge of EHEC and to identify the important research gaps in the collective understanding of the factors that lead to EHEC colonisation and transmission in ruminants.
The role of ‘supershedders’ – cattle that excrete particularly high levels of E coli O157 in their faeces – was one of the main issues discussed. Such animals are thought to play an important role in the spread of bacteria to other cattle; however, it was clear from discussions at the workshop that these animals do not form a consistent group at which interventions could be targeted.
Another conclusion from the workshop was that there is still much scientific uncertainty as to the epidemiology of EHEC within cattle herds and the roles of direct transmission between cattle, as well as the influence of bacterial and external factors on persistence in the environment.
The report notes that, among the potential intervention strategies discussed by participants in the workshop, the use of cattle vaccines was identified as a ‘clear favourite’ for further development and evaluation. Participants also noted that any widespread application of intervention strategies must take account of a proper cost-benefit evaluation, including a demonstrable impact on reducing the risk of human infection, and any health and safety risks to farm or abattoir staff or risks to the environment.
Workshop participants also suggested that there was a need to promote international collaboration in order to investigate how sequence-based typing schemes could be used to investigate the evolution and virulence of different strains, and a need to improve engagement between the industry, regulators and consumers to enhance both the understanding of the costs and benefits of intervention strategies as well as motivators and barriers to their implementation.
▪ ‘Understanding of the factors that lead to EHEC colonisation in cattle and the role of supershedding in the transmission and maintenance of infection’ can be downloaded from the FSA's website at www.food.gov.uk/multimedia/pdfs/e.coli-workshop.pdf
- British Veterinary Association