Heterogeneous Shedding of Escherichia coli 0157 in Cattle and Its Implications for Control

Identification of the relative importance of within-and betweenhost variability in infectiousness and the impact of these heterogeneities on the transmission dynamics of infectious agents can enable efficient targeting of control measures. Cattle, a major reservoir host for the zoonotic pathogen Escherichia coli 0157, are known to exhibit a high degree of heterogeneity in bacterial shedding densities. By relating bacterial count to infectiousness and fitting dynamic epidemiological models to prevalence data from a cross-sectional survey of cattle farms in Scotland, we identify a robust pattern: ≈80% of the transmission arises from the 20% most infectious individuals. We examine potential control options under a range of assumptions about within-and betweenhost variability in infection dynamics. Our results show that the within-herd basic reproduction ratio, Ro, could be reduced to