Nationwide prevalence and risk factors for faecal carriage ofEscherichia coliO157 and O26 in very young calves and adult cattle at slaughter in New Zealand

Abstract

SUMMARYNationwide prevalence and risk factors for faecal carriage ofEscherichia coliO157 and O26 in cattle were assessed in a 2-year cross-sectional study at four large slaughter plants in New Zealand. Recto-anal mucosal swab samples from a total of 695 young (aged 4–7 days) calves and 895 adult cattle were collected post-slaughter and screened with real-time polymerase chain reaction (PCR) for the presence ofE. coliO157 and O26 [Shiga toxin-producingE. coli(STEC) and non-STEC]. Co-infection with either serogroup ofE. coli(O157 or O26) was identified as a risk factor in both calves and adult cattle for being tested real-time PCR-positive forE. coliO157 or O26. As confirmed by culture isolation and molecular analysis, the overall prevalence of STEC (STEC O157 and STEC O26 combined) was significantly higher in calves [6·0% (42/695), 95% confidence interval (CI) 4·4–8·1] than in adult cattle [1·8% (16/895), 95% CI 1·1–3·0] (P< 0·001). This study is the first of its kind in New Zealand to assess the relative importance of cattle as a reservoir of STEC O157 and O26 at a national level. Epidemiological data collected will be used in the development of a risk management strategy for STEC in New Zealand.