Shiga toxin genes (stx) in Norwegian sheep herds

The aim of this study was to describe the occurrence of shiga toxic genes ( stx) in Norwegian sheep herds, and to identify herd management factors rela ted to the occurrence of stx in herds. Faecal samples from 124 sheep-herds were collected at abattoirs in 1998. Pooled samples from lambs and from ewe s were screened for stx by a PCR method directly on faeces. Of the 124 herd s, 61 were positive for stx, giving an overall herd-prevalence of 49%. Twen ty-one of the 61 positive herds were positive both in lamb and ewe samples, 24 only in lamb samples and 16 only in ewe samples. There was no differenc e in prevalence between regions. From the 21 herds positive both in lamb an d ewe samples, stx encoding E. coli were detected in 18 herds using hydroph obic grid membrane filters and subsequent colony hybridization. Information about management factors was collected by telephone interviews. Having cat tle at the same farm turned out to be a possible risk factor, with an Odds Ratio of 9.9 (CI 1.2 --> infinity).