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ARS Home » Research » Publications at this Location » Publication #96179
Title: PREVALENCE OF ESCHERICHIA COLI O157:H7 IN RANGE BEEF CALVES AT WEANING

Author
item LAEGREID, WILLIAM
item ELDER, ROBERT
item KEEN, JAMES

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: In previous studies of feedlot (FL) cattle, calves that have been the least time on feed are most likely to be shedding E. coli O157:H7. While this may be due to calves acquiring new infections on entry to the FL, this study was designed to determine prevalence of E. coli O157:H7 infection at weaning, prior to arrival at the FL or mixing with cattle from other sources. 15 range cow-calf herds which weaned calves in Oct. & Nov. were identified in Kans., Mo., Mont., Nebr. & S. Dak. Fecal & serum samples were obtained from 60 calves from each herd at weaning. Bacteriologic culture for E. coli O157:H7 was performed on fecal samples. Anti-O157 serum antibody titers were determined by blocking ELISA. 13 of 15 herds were found to have at least 1 positive isolation of E. coli O157:H7 in fecal samples. All herds had high levels of anti-O157 antibodies, with seroprevalence from 63-100%. Using sequential serum samples from 1 herd, it twas determined at least 75% of calves were seropositive through passive transfer within 2 d of birth. Seropositivity dropped to about 4% within 6 wk, then began to rise, reaching 80% at weaning. Remaining seronegative calves seroconverted within 6 wk on feed. Using seroconversion data, force of infection was calculated for each sampling interval. This analysis indicates that, in this herd, highest risk for new infection of calves was in mid- to late-summer months & dropped after weaning. This study indicates a significant number of herds are culture positive for E. coli O157:H7 at weaning. Also, serologic evidence suggests most calves have been exposed to E. coli O157 prior to weaning & all herds tested were seropositive for anti-O157 antibodies. Evidence from 1 herd suggests that risk for initial infection with E. coli O157 decreased in the early feeding period.