Environmental and food safety aspects of Escherichia coli O157 : H7 infections in cattle

The presence of E. coli O157:H7 in cattle illustrates the complex, interrel ated nature of the environment, livestock production practices, food safety , and the science of microbiology, particularly microbial ecology. Enterohe morrhagic E. coli, including E. coli O157:H7, can cause severe human diseas es that can be debilitating and life threatening. Cattle are currently cons idered to be the definitive source for E. call O157:H7 in the food supply, but this view may be simplistic and incomplete. E. coli O157:H7, appears wi despread among U.S. cattle herds, while individual animal prevalence is low and transient. Most individual animals appear to be a transient reservoir for E. coli O157:H7 although the issue of carrier animals still remains unr esolved. Epidemiological studies of the cattle production system have not c learly identified risk factors or management practices that affect E. coli O157:H7 prevalence in cattle feces. The problem of E. coli O157:H7 increase s during the summer and fall months, but the environmental factors that con tribute to this increase are poorly understood. Possible environmental fact ors that may influence E. coli O157:H7 shedding in cattle include livestock feed and waste handling practices as well as insects and microbial interac tions in soil and water. Studies of E. coli O157:H7 ecology in cattle and t he environment have been limited, but they suggest that a consideration of other independent, environmental sources of this microbe seems appropriate. The natural ecology of cholera may serve as a useful environmental model f or pursuing additional environmental research on the occurrence and transmi ssion of E. coli O157:H7 in nature.