E. coil O157 can be transmitted to humans by three primary (foodborne, environmental, waterborne) and one secondary (person-to-person transmission) pathways. A regression model and quantitative microbiological risk assessments (QMRAs) were applied to determine the relative importance of the primary transmission pathways in NE Scotland. Both approaches indicated that waterborne infection was the least important but it was unclear whether food or the environment was the main source of infection. The QMRAs over-predicted the number of cases by a factor of 30 and this could be because all E. coil O157 strains may not be equally infective and/or the level of infectivity in the dose response model was too high. The efficacy of potential risk mitigation strategies to reduce human exposure to E. coli O157 using QM RAs was simulated. Risk mitigation strategies focusing on food and environment are likely to have the biggest impact on infection figures.
The authors thank Dr Tom Reid (Foresterhill Hospital, Aberdeen) for supplying the clinical E. coli O157 case data, and Anne Thomson (University of Aberdeen) for carrying out E. coli microbiological counts from cattle and sheep faeces. The work was funded through the Economic and Social Science Research Council programme on Rural Economy and Land Use (RELU) and comments on the manuscript from the E. coli O157 RELU team are acknowledged.
- E. coli O157
- food poisoning
- risk assessment
- waterborne infection