Prevalence of shiga-toxigenic Escherichia coli O157:H7 in adult dairy cattle

John R. Dunn Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
Present address is Centers for Disease Control and Prevention, Foodborne and Diarrheal Diseases Branch, 1600 Clifton Rd, NE MS D-63, Atlanta, GA 30333.

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James E. Keen USDA, Agricultural Research Service, US Meat Animal Research Center, PO Box 166, Clay Center, NE 68933.

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R. Alex Thompson Department of Veterinary Biomedicine, Faculty of Veterinary Medicine, University of Montreal, C.P. 5000, St Hyacinthe, QC, Canada J2S 7C6.

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Abstract

Objective—To describe shiga-toxigenic Escherichia coli O157:H7 (STEC O157:H7) fecal shedding prevalence, seasonal fecal shedding patterns, and site-specific prevalence from the oral cavity, skin, and feces of dairy cattle.

Design—Cross-sectional study.

Animals—Adult dairy cattle from 13 herds in Louisiana.

Procedure—Samples were cultured for STEC O157 by use of sensitive and specific techniques, including selective broth enrichment, immunomagnetic separation, monoclonal antibody-based O:H enzyme immunoassay serotyping, and polymerase chain reaction virulence gene characterization. Point estimates and 95% confidence intervals were calculated for fecal shedding prevalence as well as site-specific prevalence from the oral cavity, skin, and feces. Logistic regression was used to assess seasonal variation and differences at various stages of lactation with respect to fecal shedding of STEC O157 in cattle sampled longitudinally.

Results—Summer prevalence in herds (n = 13) was 38.5%, with a cow-level prevalence of 6.5%. Among positive herds, prevalence ranged from 3% to 34.6%. Samples from 3 of 5 herds sampled quarterly over 1 year yielded positive results for STEC O157. In herds with STEC O157, an increase in cow-level prevalence was detected during spring (13.3%) and summer (10.5%), compared with values for fall and winter. Site-specific prevalences of STEC O157:H7 from oral cavity, skin, and fecal samples were 0%, 0.7%, and 25.2%, respectively.

Conclusions and Clinical Relevance—Our data indicated that STEC O157:H7 was commonly isolated from dairy cows in Louisiana, seasonally shed, and isolated from the skin surface but not the oral cavity of cows. (J Am Vet Med Assoc 2004;224:1151–1158)

Abstract

Objective—To describe shiga-toxigenic Escherichia coli O157:H7 (STEC O157:H7) fecal shedding prevalence, seasonal fecal shedding patterns, and site-specific prevalence from the oral cavity, skin, and feces of dairy cattle.

Design—Cross-sectional study.

Animals—Adult dairy cattle from 13 herds in Louisiana.

Procedure—Samples were cultured for STEC O157 by use of sensitive and specific techniques, including selective broth enrichment, immunomagnetic separation, monoclonal antibody-based O:H enzyme immunoassay serotyping, and polymerase chain reaction virulence gene characterization. Point estimates and 95% confidence intervals were calculated for fecal shedding prevalence as well as site-specific prevalence from the oral cavity, skin, and feces. Logistic regression was used to assess seasonal variation and differences at various stages of lactation with respect to fecal shedding of STEC O157 in cattle sampled longitudinally.

Results—Summer prevalence in herds (n = 13) was 38.5%, with a cow-level prevalence of 6.5%. Among positive herds, prevalence ranged from 3% to 34.6%. Samples from 3 of 5 herds sampled quarterly over 1 year yielded positive results for STEC O157. In herds with STEC O157, an increase in cow-level prevalence was detected during spring (13.3%) and summer (10.5%), compared with values for fall and winter. Site-specific prevalences of STEC O157:H7 from oral cavity, skin, and fecal samples were 0%, 0.7%, and 25.2%, respectively.

Conclusions and Clinical Relevance—Our data indicated that STEC O157:H7 was commonly isolated from dairy cows in Louisiana, seasonally shed, and isolated from the skin surface but not the oral cavity of cows. (J Am Vet Med Assoc 2004;224:1151–1158)

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