Transmission of F4+ E. coli in groups of early weaned piglets.

The aim of this study was to estimate transmission parameters of enterotoxigenic F4+ Escherichia coli F4 (F4+ E. coli) in groups of early weaned piglets with F4-receptor-positive (F4R+) and F4-receptor-negative piglets (F4R-). Transmission of F4+ E. coli was quantified in four heterogeneous groups of F4R+ and F4R- piglets. Infectiousness was determined by the number of F4+ E. coli/g faeces shed during 8 days. Transmission parameters were estimated using generalized linear models assuming a stochastic SIR model. F4R+ piglets were found to be more susceptible than F4R- piglets, but F4R+ and F4R- piglets were not different in infectiousness. The reproduction ratios for homogeneous F4R+ and F4R- populations were estimated as 6.37 (95% CI 1.89-21.48) and 0.02 (95% CI 0.00-1.13) respectively. The implication of these results is that in order to prevent major outbreaks, the fraction of F4R+ piglets should be small (approximately 10% or less). Therefore, selective breeding programmes could contribute to reducing F4+ E. coli-related diarrhoea and transmission.