The report from the so-called “supershedders” conference on the future of enterohaemorrhagic Escherichia coli (EHEC) research — held recently in Scotland — is out. It identifies key knowledge gaps and recommends areas for future research.
The workshop stemmed from the controversial 2005 E. coli outbreak in South Wales and was organized by the Food Standards Agency in Scotland, the Knowledge Transfer Network Biosciences and the University of Edinburgh.
The report focusing on the future of E. coli research was published by Scotland’s Food Safety Agency. The workshop’s goal was to reduce the health impact of the pathogen on humans by tacking it at the source.
Experts from around the globe attended the workshop in Midlothian, where priorities were agreed for research to help tackle EHEC at the main source of infection, the cattle gut.
Delegates shared knowledge of the factors leading to the transmission and maintenance of infection in cattle, particularly the role of ‘supershedders’ – cattle that excrete particularly high levels of E.coli O157 in their feces.
Supershedders are thought to play an important role in the spread of the bacteria to other cattle and the likelihood of transmission to humans via the environment or raw food.
There was also discussion on intervention strategies being explored in other countries to reduce EHEC shedding by cattle and the feasibility of introducing these in the UK.
The main source for EHEC is the gut of ruminant animals, particularly cattle, which excrete or shed the bacteria in their feces.
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 feces in the environment or when fecal contamination enters the water supply or food chain
The key recommendations in the report include:
- Improve understanding of the epidemiology of EHEC infection in cattle, humans and environmental reservoirs the need for more studies on the biology of host-bacteria interactions and the relationships between cattle, the environment and human infection rates.
- Support further research on potential intervention strategies and how effective they need to be to have an impact on human health.
- Promote international collaboration to investigate how sequence based typing schemes can be used to investigate the evolution and virulence of strains
- Improve engagement between the industry, regulators and consumers to enhance understanding of the cost/benefit of intervention strategies as well as motivators and barriers to their implementation.
The 2005 E. coli outbreak was the largest ever experienced in Wales and the second largest in the history of the United Kingdom. It was best known for the death of 5-year-old Mason Jones, and involved a total of 157 cases, mostly children from 44 schools.
Because of the controversy generated by the outbreak, Professor Hugh Pennington was enlisted to conduct a public inquiry into the tragedy. He produced a 45,000-page record, concluding the source of the contamination of a butcher serving the schools, John Tudor & Sons.
Among its recommendations, the Pennington inquiry called for exploring the feasibility of identifying “supershedder” cattle on farms “as a potential means of reducing the likelihood of spreading E.coli O157 to other cattle.”
E. coli O156:H7 is the best known among Enterohaemorrhagic E.coli (EHEC), the group that also includes the “Big Six” E. coli strains: O26, O111, O103, O121, O45 and O145.
In the United States, the U.S. Department of Agriculture does not permit O157:H7 or any of the “Big Six” in meat. If any of these strains are consumed, they can result in mild to severe symptoms including abdominal cramps, vomiting and sometimes-bloody diarrhea
EHEC infections can also lead to serious complications including hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. These conditions affect the blood, kidneys and, in severe cases, the central nervous system, and can even lead to death.
The United Kingdome experiences about 1,000 E. coli infections annually, with most being attributed to O157:H7,
Controlling the spread of E. coli is a priority for FSA.
Photo: Mason Jones, Age 5© Food Safety News