The prevalence of Shiga toxin-producing Escherichia coli in cattle and sheep in the lower North Island, New Zealand

Abstract

AIM: To genotype Escherichia coli cultured from the faeces of healthy cattle and sheep in the lower North Island, in order to investigate the possible role of ruminants as a reservoir for Shiga toxin-producing E. coli (STEC) in New Zealand.

METHODS: A total of 952 strains of E. coli were isolated on selective media, from faecal swabs from 319 animals (187 cattle and 132 sheep) from four sites in the Manawatu and Rangitikei regions of New Zealand. A multiplex polymerase chain reaction (PCR) was used to genotype the E. coli isolates, using amplification of Shiga toxin genes (stx1 and stx2) and the E. coli attaching and effacing gene (eae).

RESULTS: Isolates of E. coli were cultured from swabs from 178/187 (95.2%) cattle and all 132 (100%) sheep. Ninety-nine (10.4%) of the isolates were stx1 only, 83 (8.7%) stx2 only, 33 (3.5%) stx1 and stx2, 23 (2.4%) stx1 and eae, one (0.1%) stx2 and eae, and 115 (12.1%) were eae only. Overall, 51 (27.3%) cattle and 87 (65.9%) sheep were stx-positive, whereas 69 (36.9%) cattle and 36 (27.3%) sheep were eae-positive.

CONCLUSIONS: Both healthy cattle and sheep are asymptomatic reservoirs of STEC in New Zealand. Direct contact with cattle and sheep or consumption of water or foodstuffs contaminated with cattle of sheep faeces may represent a significant source of infection for humans.

KEY WORDS:

• Shiga toxin-producing Escherichia coli
• STEC
• stx
• eae
• cattle
• sheep
• ruminant
• food safety
• public health

Acknowledgements

This study was funded through AgResearch Repositioning funds. Sam Taylor was the recipient of an AgResearch Summer Studentship. We acknowledge the assistance of Steve Lees, Colin Faiers, Dan Robinson, Neville Grace, Scott Knowles, Jacalyn Scott and Graham McCool for animal sampling. We thank Zaneta Park-Ng for excellent statistical assistance. We also thank Fiona Thomson-Carter and Jenny Bennett for their helpful advice and enthusiasm in performing this work.

Notes

¹ J Bennett, Environmental Science and Research Ltd, Porirua, New Zealand