E.coli O157 colonisation and shedding in cattle

Escherichia coli O157 is an important zoonotic organism with a global distribution. E.coli O157 can cause severe disease in humans and while the prevalence of human disease attributed to E.coli O157 is low in Australia, presence of this pathogen on meat exported to the USA can result in trade restrictions. Greater understanding of the distribution of E.coli O157 in cattle and the variation over time of shedding and ‘super-shedding’ of this organism from cattle was required within Australian production systems. In order to achieve this, after an initial period of laboratory methods validation and skill enhancement, two systems were investigated in a longitudinal manner – an extensive beef cattle production system (at Charles Sturt University) and a dairy replacement herd (at University of Sydney). Cattle within these herds were followed longitudinally for a number of months with repeated sampling twice a week during this time. In addition, more intensive sampling was also performed daily and twice daily over a period of weeks at both sites. An expert opinion elicitation exercise was also performed, where international experts in the area of E.coli O157 were questioned on multiple areas surrounding shedding of the pathogen, super shedding, risk factors and potential control measures. Finally, a number of simulation models were specified to identify the ability to pool samples in order to reduce the cost of future longitudinal studies, and also to identify key interventions for reduction of prevalence of carcass contamination with E.coli O157, in light of the findings of the current research.