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Title: PREVALENCE OF SHIGA-TOXIGENIC ESCHERICHIA COLI O157:H7 IN ADULT DAIRY CATTLE

Author
item DUNN, JOHN - LOUISIANA STATE UNIV
item Keen, James
item THOMPSON, ALEX - UNIVERSITY OF MONTREAL

Submitted to: Journal of the American Veterinary Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2003
Publication Date: 4/1/2004
Citation: DUNN, J.R., KEEN, J.E., THOMPSON, A.R. PREVALENCE OF SHIGA-TOXIGENIC ESCHERICHIA COLI O157:H7 IN ADULT DAIRY CATTLE. JOURNAL OF THE AMERICAN VETERINARY MEDICAL ASSOCIATION. 2004. V. 224. P. 1151-1158.

Interpretive Summary: Dairy cattle shedding shiga-toxigenic Eshcherichia coli O157:H7 (STEC O157:H7) have been associated with human infections. Cross-sectional studies in Louisiana dairy cattle were designed to estimate the prevalence of STEC O157:H7 fecal shedding, describe seasonal shedding patterns, and estimate site-specific prevalence from the mouth, hide, and feces. Fecal prevalence in herds (n=13), sampled during the summer, was 38.5%, with a cow-level prevalence of 6.5%. Among positive herds, prevalence ranged from 3%-34.6%. Three of five herds sampled longitudinally were positive. Among positive herds an increase in cow-level prevalence occurred during spring (13.3%) and summer (10.5%). Site-specific cow-level prevalence of STEC O157:H7 from mouth, hide, and fecal samples was 0%, 0.7% and 25.2%, respectively. STEC O157:H7 was seasonally shed, commonly isolated from cows and herds, and found colonizing the hide. These findings have implications for controlling transmission, and understanding seasonal shedding patterns and geographic variation of STEC O157:H7 colonization of cattle.

Technical 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 mouth, hide, and feces in Louisiana dairy cattle. Design - Cross-sectional study designs. Animals - Adult dairy cattle from 13 Louisiana herds. Procedure - Samples were cultured for STEC O157 using sensitive and specific techniques, including selective broth enrichment, immunomagnetic separation (IMS), 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 point prevalence as well as site-specific prevalence from the mouth, hide, and feces. Logistic regression was used to assess seasonal variation and differences among cattle at various stages of lactation with respect to fecal shedding of STEC O157. 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%-34.6%. Three of five (60%) herds sampled longitudinally were positive. Within positive herds an increase in cow-level prevalence was detected during spring (13.3%) and summer (10.5%) compared to fall and winter. Site-specific cow-level prevalence of STEC O157:H7 from mouth, hide, and fecal samples was 0%, 0.7% and 25.2%, respectively. Conclusions and Clinical Relevance - STEC O157:H7 was commonly isolated from Louisiana dairy cows and herds, was seasonally shed, and isolated from the hide surface but not the oral cavity.