CANADIAN PERSPECTIVES ON VEROCYTOTOXIN-PRODUCING ESCHERICHIA-COLI INFECTION

Infection with verocytotoxin-producing Escherichia coli (VTEC) became nationally reportable in 1990. Between 1990 and 1994, the national inc idence of reported infections ranged from 3 to 5.3 per 100,000 inhabit ants. Most cases are sporadic and are caused by E. coli O157:H7. Recen t investigations have identified that, in addition to exposure to unde rcooked ground beef, contact with cattle, consumption of well water, a nd exposure to rural environments are important risk factors for VTEC infection. Also, results of case-control studies and detection of asym ptomatic fecal carriage of E. coli O157:H7 and other VTEC in farm fami ly members and abattoir workers have led to an increasing emphasis on person-to-person spread in the epidemiology of VTEC infection. Control ling E. coli O157:H7 and other VTEC at the farm level may therefore ha ve a broader impact than simply reducing the risk of foodborne VTEC in fection. Longitudinal studies on dairy farms have demonstrated that E. coli O157:H7 carriage by cattle at the farm and animal level is often transient, and that cattle, rather than the farm environment, are the major reservoir for this organism on dairy farms. Small herds that ar e controlled by traditional management practices have the highest risk for VTEC infection. Further studies are likely to result in developme nt of effective strategies to control VTEC at the farm level.