Distribution of Escherichia coli O157:H7 within and among cattle operations in pasture-based agricultural areas

OBJECTIVE: To determine the distribution of Escherichia coli O157:H7 in pasture-based cattle production areas. SAMPLE POPULATION: Two 100-km2 agricultural areas consisting of 207 pasture, 14 beef-confinement, and 3 dairy locations within 24 cattle operations. PROCEDURE: 13,726 samples from cattle, wildlife, and water sources were obtained during an 11-month period. Escherichia coli O157:H7 was identified by use of culture and polymerase chain reaction assays and characterized by pulsed-field gel electrophoresis (PFGE). RESULTS: Odds of recovering E coli O157:H7 from feeder-aged cattle were > 4 times the odds for cow-calf or dairy cattle. There was no difference in prevalence for pastured versus confined cattle after controlling for production age group. Number of samples collected (37 to 4,829), samples that yielded E coli O157:H7 (0 to 53), and PFGE subtypes (0 to 48) for each operation varied and were highly correlated. Although most PFGE subtypes were only detected once, 17 subtypes were detected on more than 1 operation. Ten of 12 operations at which E coli O157:H7 was detected had at least 1 subtype that also was detected on another operation. We did not detect differences in the probability of having the same subtype for adjacent operations, nonadjacent operations in the same study area, or operations in the other study area. CONCLUSIONS AND CLINICAL RELEVANCE: Strategies aimed at controlling E coli O157:H7 and specific subtypes should account for the widespread distribution and higher prevalence in feeder-aged cattle regardless of production environment and the fact that adjacent and distant cattle operations can have similar subtypes.