A LONGITUDINAL-STUDY OF ESCHERICHIA-COLI-O157 IN 14 CATTLE HERDS

Escherichia coil O157 shedding in 14 cattle herds was determined by fa ecal culture at intervals of approximately 1 month for up to 13 months . The overall prevalence was 1.0% (113/10832 faecal samples) and 9 of the 14 herds were detected as positive. Herds positive 2 years previou sly (n = 5) had a higher prevalence of positive cattle (median = 1.9 % ) than herds which had been negative on a previous sampling (n = 8, me dian = 0.2 %). Weaned heifers had a higher prevalence (1.8 %) than did unweaned calves (0.9 %) or adults (0.4 %). For all herds the highest prevalence occurred in the summer months, which resulted in most of th e positive faecal samples being collected on a minority of sampling vi sits.