Epidemiology and Infection



Escherichia coli O157[ratio]H7 infection in cows and calves in a beef cattle herd in Alberta, Canada


V. P. J.  GANNON  a1 c1, T. A.  GRAHAM  a1, R.  KING  a2, P.  MICHEL  a3, S.  READ  a3, K.  ZIEBELL  a3 and R. P.  JOHNSON  a3
a1 Health Canada, Animal Diseases Research Institute, Lethbridge, Alberta, Canada T1J 3Z4
a2 The Canadian Food Inspection Agency, Animal Diseases Research Institute, Lethbridge, Alberta, Canada T1J 3Z4
a3 Health Canada, Laboratory Centre for Enteric and Zoonotic Diseases, Guelph, Ontario, Canada N1G 3W4

Abstract

Escherichia coli O157[ratio]H7 infection of cows and calves in a naturally-infected beef cattle herd in Alberta, Canada, was investigated over 2 years, encompassing two calf production cycles. In both years of the study, E. coli O157[ratio]H7 was isolated from the faeces of cows shortly after but not before parturition in late winter: 6/38 (16%) in 1996 and 13/50 (26%) in 1997. At <1 week post-partum, 13/52 (25%) calves born in 1997 were shedding the organism. Faecal shedding of E. coli O157[ratio]H7 by cows and calves continued over the 7 weeks that they were in the calving pens, with the organism being isolated from the faeces of 2–18% of cows and 23–26% of calves during this period. Five weeks after they were moved onto a native grass pasture, all the calves and all but one cow in 1997 had ceased shedding the organism. When the calves were weaned in the fall, E. coli O157[ratio]H7 was isolated from the faeces of 0–1.5% of the calves 1 week prior to weaning and from 6–14% of the calves within 2 weeks after weaning. Parturition, calving pens and weaning appear to be important factors in maintaining E. coli O157[ratio]H7 infections in this beef cattle herd. Isolates from cows and calves during the immediate post-partum period were mostly of the same pulsed-field gel electrophoresis (PFGE) type of E. coli O157[ratio]H7. Similarly, at weaning a common PFGE type of E. coli O157[ratio]H7, which differed slightly from the post-partum PFGE type, was isolated from the calves. These typing data suggest a common source of infection for the animals as well as demonstrate clonal turnover of resident populations of this pathogen.

(Accepted February 25 2002)


Correspondence:
c1 Author for correspondence.


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