Author:
MECHIE S. C.,CHAPMAN P. A.,SIDDONS C. A.
Abstract
A dairy herd associated with Escherichia coli O157
infection in humans was studied for the 15 months following the
outbreak to examine seasonal, age and management factors affecting
faecal excretion of the organism and to determine the mode and
frequency of milk contamination with the organism. Between May 1993
and July 1994, 28 visits were made to the farm to collect a total of
3593 rectal swabs from cows, heifers and calves and 329 milk samples.
E. coli O157:H7 was isolated from 153 (4·3%)
of 3593 bovine rectal swabs. The maximum prevalence at any one visit
was 14% in lactating cows, 40% in non-lactating cows, 56% in calves
and 68% in heifers. The prevalence in lactating cows, which was
significantly lower than in the other groups, peaked during
May–July 1993 and again briefly after the cattle were housed
during November 1993 and then again during May 1994. Excretion rates
of E. coli O157:H7 in lactating cows were highest
during the first month after calving, falling during lactation and
rising to another peak at 7 months postpartum. Between November 1993
and May 1994 there was no evidence of excretion in any group.
Eighty-seven (74%) of the animals which excreted E. coli
O157:H7 did so on only one occasion but 23 (32%) of 73 cows
and heifers and 7 (16%) of 44 calves which excreted the organism did
so on more than one occasion. E. coli O157:H7 was not
isolated from milk taken from the bulk tank but it was isolated from
individual milk samples (one milk jar and one fore-milk) from two
animals previously shown to be faecal excretors of the organism. All
isolates of E. coli O157:H7 obtained were of the same
phage type, toxin genotype and plasmid profile.
Publisher
Cambridge University Press (CUP)
Subject
Infectious Diseases,Epidemiology
Cited by
220 articles.
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