Water-associated Verocytotoxigenic E. coli in Ireland

Verocytotoxigenic Escherichia coli (VTEC) also referred to Shiga toxigenic E. coli (STEC) are pathogenic E. coli that cause infectious diarrhoea that in some people is associated with the life threatening complication Haemolytic Uraemic Syndrome (HUS). HUS is associated with renal failure, red blood cell lysis and risk of death. VTEC represents a major threat to public health worldwide. A significant part of the public health challenge in relation to VTEC is the evidence that some VTEC are much more likely to be associated with HUS than others. A public health response that treats all VTEC infections as equivalent in risk imposes greatburdens (social and financial) on families of those infected and on health care systems. The incidence of laboratory detected human infection due to VTEC in Ireland has been the highest in Europe since 2008 increasing from 1.4/100,000 in 2004 to 15.9.1/100,000 in 2015 (1, 2).

The most common modes of transmission are person-to-person and waterborne, however, for approximately 50% of cases each year, the mode of transmission is reported as unknown or unspecified. Identification of the source, mode of transmission and differential pathogenicity of VTEC strains is essential to ensure an effectively targeted public health response that minimises social and financial costs for those infected with relatively low risk VTEC strains.

The aims of this project, which is an Irish Research Council funded fellowship of Dr Carina Brehony, are to examine the relative contribution of water supply to VTEC infection as this is important in planning an effective public health response and to assess strain diversity and correlate this with clinical outcome. This will be achieved by:

1) determining the spatial and temporal incidence of human infection with VTEC within a selected a Health Service Region in Ireland using Geographical Information Systems (GIS) to identify areas of high incidence (hotspot) and low incidence (coldspot);

2) using GIS to correlate data on land use with age-adjusted incidence of human infection;

3) examining the extent of contamination of water supplies of households in “hotspots” and “coldspots” (using the CapE method)(3) resulting in a preliminary qualitative assessment of the relative importance of water with VTEC to the occurrence of infection; and

4) isolating and sequencing the whole genome of selected groups of apparently related clinical and environmental isolates of VTEC to determine relatedness, transmission pathways and potentially pathogenicity of particular strains.

1. NVRLS. Annual Report of the National VTEC Service, 2011
2. HPSC. Health Protection Surveillance Centre Annual Report, 2015
3. Morris D, Kavanagh S, Carney K, MacDomhnaill B, Cormican M. 2016. CapE (capture, amplify, extract): A rapid method for detection of low level contamination of water with Verocytotoxigenic Escherichia coli (VTEC). Sci Total Environ 563:267–272.