Results of a longitudinal study of the prevalence of Escherichia coli O157: H7 on cow-calf farms

Objective-To describe the frequency and distribution of Escherichia coli O1 57:H7 in the feces and environment of cow-calf herds housed on pasture. Sample Population-Fecal and water samples for 10 cow-calf farms in Kansas. Procedure-Fecal and water samples were obtained monthly throughout a 1-year period (3,152 fecal samples from 2,058 cattle; 199 water samples). Escheri chia coli O157:H7 in fecal and water samples was determined, using microbia l culture. Results-Escherichia coli O157:H7 was detected in 40 of 3,152 (1.3%) fecal s amples, and 40 of 2,058 (1.9%) cattle had greater than or equal to1 sample with E coil. Fecal shedding by specific cattle was transient; none of the c attle had E coli in more than 1 sample. Significant differences were not de tected in overall prevalence among farms. However, significant differences were detected in prevalence among sample collection dates. Escherichia coli O157:H7 was detected in 3 of 199 (1.5%) water samples. Conclusions and Clinical Relevance-Implementing control strategies for E co li O157:H7 at all levels of the cattle industry will decrease the risk of t his organism entering the human food chain. Devising effective on-farm stra tegies to control E coil O157:H7 in cow-calf herds will require an understa nding of the epidemiologic characteristics of this pathogen.