title: Factors Associated with Shiga Toxin-Producing Escherichia coli Shedding by Dairy and Beef Cattle.
abstract: Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen that can cause hemorrhagic colitis and hemolytic-uremic syndrome. Cattle are the primary reservoir for STEC, and food or water contaminated with cattle feces is the most common source of infections in humans. Consequently, we conducted a cross-sectional study of 1,096 cattle in six dairy herds (n = 718 animals) and five beef herds (n = 378 animals) in the summers of 2011 and 2012 to identify epidemiological factors associated with shedding. Fecal samples were obtained from each animal and cultured for STEC. Multivariate analyses were performed to identify risk factors associated with STEC positivity. The prevalence of STEC was higher in beef cattle (21%) than dairy cattle (13%) (odds ratio [OR], 1.76; 95% confidence interval [CI], 1.25, 2.47), with considerable variation occurring across herds (range, 6% to 54%). Dairy cattle were significantly more likely to shed STEC when the average temperature was >28.9°C 1 to 5 days prior to sampling (OR, 2.5; 95% CI, 1.25, 4.91), during their first lactation (OR, 1.8; 95% CI, 1.1, 2.8), and when they were <30 days in milk (OR, 3.9; 95% CI, 2.1, 7.2). These data suggest that the stress or the negative energy balance associated with lactation may result in increased STEC shedding frequencies in Michigan during the warm summer months. Future prevention strategies aimed at reducing stress during lactation or isolating high-risk animals could be implemented to reduce herd-level shedding levels and avoid transmission of STEC to susceptible animals and people.
  
  
  
  STEC shedding frequencies vary considerably across cattle herds in Michigan, and the shedding frequency of strains belonging to non-O157 serotypes far exceeds the shedding frequency of O157 strains, which is congruent with human infections in the state. Dairy cattle sampled at higher temperatures, in their first lactation, and early in the milk production stage were significantly more likely to shed STEC, which could be due to stress or a negative energy balance. Future studies should focus on the isolation of high-risk animals to decrease herd shedding levels and the potential for contamination of the food supply.
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Cristina
authors.initials: C
authors.lastname: Venegas-Vargas
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Henderson
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Akanksha
authors.initials: A
authors.lastname: Khare
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Rebekah E
authors.initials: RE
authors.lastname: Mosci
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Lehnert
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Pallavi
authors.initials: P
authors.lastname: Singh
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Ouellette
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Norby
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Funk
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Rust
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Bartlett
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Grooms
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA mannin71@msu.edu.
authors.forename: Shannon D
authors.initials: SD
authors.lastname: Manning
mesh_terms: D000818:Animals; D057138:Bacterial Shedding; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology; D003430:Cross-Sectional Studies; D003612:Dairying; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D005260:Female; D006463:Hemolytic-Uremic Syndrome / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D008824:Michigan / Q000453:epidemiology; D015995:Prevalence; D054323:Shiga-Toxigenic Escherichia coli / Q000502:physiology*