Escherichia coli O157:H7 in healthy dairy cows

Faecal samples were taken from 371 cows originating from 55 dairy farms and slaughtered at one slaughterhouse; tonsils were taken from 215 of these animals. Escherichia coli O157:H7 was found in the faeces of only two animals and was not found in any tonsils. The farm supplying the first positive cow detected at the slaughterhouse was Visited 3 months later and 160 animals (80 cows and 80 heifers) were tested by rectal swabs; E. coli O157:H7 was not isolated.