Prevalence of Shiga-toxigenic Escherichia coli O157:H7 in adult dairy cattle.
OBJECTIVE
To describe shiga-toxigenic Escherichia coil 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.


METHODS
Cross-sectional study.


METHODS
Adult dairy cattle from 13 herds in Louisiana.


METHODS
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 in = 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
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.
Dunn
John R
JR
Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
Keen
James E
JE
Thompson
R Alex
RA
D000818:Animals; D015373:Bacterial Typing Techniques / Q000662:veterinary; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology; D015169:Colony Count, Microbial / Q000379:methods / Q000662:veterinary; D003430:Cross-Sectional Studies; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000302:isolation & purification* / Q000472:pathogenicity; D005243:Feces / Q000382:microbiology; D005260:Female; D016015:Logistic Models; D008137:Longitudinal Studies; D008145:Louisiana / Q000453:epidemiology; D009055:Mouth / Q000382:microbiology; D015995:Prevalence; D012621:Seasons; D022603:Shiga Toxins / Q000096:biosynthesis; D012867:Skin / Q000382:microbiology
D022603:Shiga Toxins