Prevalence of verotoxigenic Escherichia coli O157:H7 in fecal and ear samples from slaughtered cattle in Sweden.

A national verotoxigenic Escherichia coli (VTEC) O157:H7 monitoring study was carried out among cattle at slaughter in Sweden during 2005 and 2006. Sixty (3.4%; 95% confidence interval, 3.3 to 3.5%) of 1,758 fecal samples collected and 54 (12%; 95% confidence interval, 11.9 to 12.4 %) of 446 ear samples tested positive for VTEC O157:H7. Ear samples were included to evaluate whether they could be used to assess general VTEC O157:H7 contamination at slaughter. The respective prevalences of positive fecal and ear samples were 16 and 21% for older calves, 3.5 and 10% for young stock, and 1.6 and 12% for adult cattle. There were significant differences between the age groups for the fecal samples, but not for the ear samples. It could be that ear samples are less subject to age variations due to environmental factors, or perhaps this observation was due to fewer ear samples being collected in this study. Within the age groups, the prevalence of VTEC O157:H7-positive ear samples was significantly higher than that of fecal samples for young stock and adult cattle. Furthermore, the prevalence of positive ear samples fluctuated more widely throughout the year than that of positive fecal samples. The fecal prevalence data can be used as baseline data against which future intervention strategies can be evaluated, and the ear samples can be used as an indicator of environmental contamination. The results of the ear samples are too limited to determine if they can be used to detect hide contamination and risk of carcass contamination.