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Escherichia coli O157:H7 is a human pathogen associated with haemolytic uraemic syndrome and haemorrhagic colitis cases throughout the developed world (García and others 2010). The faeces of ruminant animals, in particular cattle and sheep, are regarded as the primary reservoir of E coli O157:H7. Contact with ruminant faeces either directly (eg, in the environment) or indirectly (eg, ingestion of contaminated meat products) plays a central epidemiological role in human E coli O157 infections. As a result, there has been considerable effort to increase our understanding of colonisation patterns in ruminants. Studies have shown that livestock infection and colonisation is transient and seasonal (Paiba and others 2002), and that it is affected by multiple factors including stress and diet (Jones 1999). A comparison of different studies also implies that there are substantial regional differences in carriage rates. Spatial variation is also known to occur in the frequency of human E coli O157 infection; for instance, the rate of infection is considerably greater (4–10 times) in Scotland than in Wales even though both countries appear to be similar in terms of population demographics, geography and diet (Jones and others 2011). Attempts to explain this phenomenon have looked at possible social and epidemiological factors (Jones and others 2011, Strachan and others 2011, Rotariu and others 2012), but there remains more fundamental research to be done on prevalence rates within the animal reservoir. The aim of this study was to examine fresh cattle and sheep faeces from farms in Gwynedd, North Wales, for total coliforms, E coli and E coli O157 bacteria, over a 12-month period.
Samples of freshly excreted sheep and cattle faecal material were collected monthly from September 2010 to August 2011 (total n=150 for sheep and 150 for cattle) from 25 lowland or upland farms, all within …