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Title: SHIGA-TOXIGENIC ESCHERICHIA COLI O157:H7 IN LOUISIANA DAIRY HERDS

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

Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/24/2002
Publication Date: 11/10/2002
Citation: DUNN, J.R., KEEN, J.E., THOMPSON, R.A. SHIGA-TOXIGENIC ESCHERICHIA COLI O157:H7 IN LOUISIANA DAIRY HERDS. RESEARCH WORKERS IN ANIMAL DISEASES CONFERENCE PROCEEDINGS. 2002. Abstract No. 38P.

Interpretive Summary:

Technical Abstract: Dairy cattle shedding shiga-toxigenic Eshcherichia coli O157:H7 (STEC O157:H7) have been associated with infection of humans. US population-adjusted incidence estimates indicate that human cases occur more commonly in northern states. Few studies have been conducted in southern cattle herds and little is known regarding differential geographic patterns that may exist. Adult dairy cattle have generally been thought to be colonized at low prevalence. Seasonal increases in dairy cattle fecal shedding, and colonization of the oral cavity and hide surfaces in beef feedlot cattle have been demonstrated. Cross-sectional studies in Louisiana dairy herds were designed to 1) estimate cow-level and herd-level point prevalence of STEC O157:H7 fecal shedding, 2) describe seasonal shedding patterns in 5 herds sampled over 1 year and 3) estimate the site-specific point prevalence in the oral cavity and on the dorsal hide surface. Samples were cultured using selective enrichment, IMS and ctSMAC. Suspect colonies were confirmed and characterized. The point prevalence estimate 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% to 34.6%. Three of 5 herds sampled over 1 year had at least 1 positive cow during the study. Among positive herds an increase in cow-level prevalence was detected during spring (13.3%) and summer (10.5%). Cow-level prevalence estimates of STEC O157:H7 in the oral cavity, on the dorsal hide surface and from feces were 0%, 0.7% and 25.2%, respectively. Results suggest that Louisiana dairy cattle seasonally shed STEC O157:H7, prevalence can be high and that it can be found on hide surfaces. These finding have implications for controlling foodborne, waterborne and direct contact transmission of STEC O157:H7 in Louisiana, in addition to implications regarding seasonal shedding patterns and geographic variation of STEC O157:H7 colonization of cattle.