| We conducted two observational field studies to investigate the epidemiology of the human pathogen, Escherichia coli O157, in range cattle production environments. In a cross-sectional study of free-ranging deer, 25% of successful hunters in a 25,600-km2 area submitted feces from harvested deer. Four (0.25%) of 1,608 samples were E. coli O157:H7 culture positive. We were unable to detect a significant geographic distribution pattern of E. coli O157:H7.; We conducted a longitudinal study to determine the genetic diversity, frequency, persistence, and distribution of E. coli O157 in predominately range environments. We collected 13,726 cattle fecal, water source, and wildlife fecal samples over an 11-month period from 225 locations (209 pasture, 13 feedlot and 3 dairy) on 24 cattle operations in two areas. Isolates (237) from 93 samples were recovered by culture/latex agglutination and confirmed as E. coli O157 by PCR. We detected 79 unique patterns or subtypes from 235 typeable isolates by pulsed-field gel electrophoresis of XbaI digested DNA (XbaI/PFGE).; The E. coli O157 prevalence was higher for cattle samples than for water source samples (P < 0.01), and also was higher in feedlot locations than in pasture locations (P = 0.03). Wide ranges in samples collected (37 to 4829), E. coli O157 positive samples (0 to 53), and XbaI/PFGE subtypes (0 to 48) occurred among operations.; Although most XbaI/PFGE subtypes were only detected once (54), ten recurring subtypes represented the majority of isolates. Subtypes were recovered from up to 10 dates/locations, and up to 10 months apart. Seventeen subtypes were detected on multiple operations. Furthermore, 10 of 12 operations where E. coli O157 was detected had at least one subtype, which also was detected on another operation in either the same or different study areas. Eight subtypes were detected in cattle as well as water (tanks, ponds, or creeks) and/or wildlife (opossum).; The results suggest that potential programs aimed at controlling or tracing E. coli O157 (XbaI/PFGE subtypes) in range cattle areas should focus on the entire local ecosystem, should not be restricted to one or few cattle operations, and should recognize the potential for regional transmission. |
