EnterohemorrhagicEscherichia coliO157: epidemiology and ecology in bovine production environments

Abstract

AbstractEnterohemorrhagicEscherichia coli, particularly the O157(:H7) serogroup, has become a worldwide public health concern. Since cattle feces are often implicated as the source ofE. coliO157 in human infections, considerable resources have been devoted to defining the epidemiology and ecology ofE. coliO157 in cattle environments so that control might begin at the farm level. Diagnostic limitations and the complexity of often interrelated microbial, animal, herd, environmental and production factors have hindered the determination of the epidemiology, ecology and subsequent farm-level control ofE. coliO157. The widespread distribution ofE. coliO157, the transitory nature of fecal shedding, multiple potential environmental sources, lack of species specificity, and age-, feed- and time-related differences in cattle prevalence are documented. However, the significance and/or role of these factors in the epidemiology and ecology ofE. coliO157 is still unclear. Cattle are a major source ofE. coliO157, but it may be simplistic to believe that most herds are relatively closed systems with small percentages of cattle serving as true reservoirs. Practical on-farm control may require explicit definitions of the seemingly complex system(s) and the microbial, animal, herd, environmental and production factors involved in the multiplication, maintenance and transmission ofE. coliO157.