Daily shedding dynamics ofE. coliO157 in an Australian grass-fed beef herd

Abstract

SUMMARYThis study aimed to describe the diurnal shedding dynamics ofEscherichia coliO157 in cattle managed on pasture. The purpose was to identify the value of a single measurement for predicting the shedding status on subsequent days. Over a 14-day period, 24 beef cows with knownE. coliO157 shedding status were sampled twice daily or daily (21 sampling points) andE. coliO157 was enumerated from faeces. No association between shedding status of individual animals within a 7-h period was identified (odds ratio 1·5,P= 0·08). Short-interval sampling demonstrated substantial diurnal volatility in shedding ofE. coliO157 that is not evident in studies based on long-interval (>7 days) sampling. The findings contribute to and support previous findings on the question why it has been difficult to achieve progress in understanding the epidemiology ofE. coliO157 infection in cattle.