Association between animal age and the prevalence of Shiga toxin-producing Escherichia coli in a cohort of beef cattle Raies A. Mir a,b , Thomas A. Weppelmann b,c , Minyoung Kang a,b , Todd M. Bliss a,b , Nicolas DiLorenzo d , G. Cliff Lamb d , Soohyoun Ahn e , Kwang Cheol Jeong a,b, * a Department of Animal Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, United States b Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, United States c Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, FL 32611, United States d North Florida Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Marianna, FL 32446, United States e Food Science and Human Nutrition Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, United States 1. Introduction Even though progress has been made to reduce the incidence of diseases caused by foodborne pathogens, they remain of great economic and public health concerns. The Centers for Disease Control and Prevention (CDC) has estimated that pathogenic Shiga-toxin producing Escher- ichia coli (STEC) cause about 269,000 cases of illnesses (including ca. 3700 hospitalizations and 30 deaths) in the United States every year (Scallan et al., 2011). Among STEC serotypes, E. coli O157:H7 is the most well-known and can cause hemorrhagic colitis, bloody diarrhea, and hemolytic uremic syndrome (HUS) in humans (Kaper et al., 2004). Non-O157 STEC serogroups, such as O26, O45, O103, O111, Veterinary Microbiology xxx (2014) xxx–xxx A R T I C L E I N F O Article history: Received 28 July 2014 Received in revised form 27 November 2014 Accepted 15 December 2014 Keywords: STEC Pre-harvest food safety Animal factors Prevalence, Age A B S T R A C T Even with advancements in pre- and post-harvest food safety, Shiga toxin-producing Escherichia coli (STEC) still present challenges to human health. Since cattle are the primary reservoir for STEC, lowering the prevalence of this pathogen in farm animals may reduce STEC outbreaks in humans. However, because many of the factors that modulate the colonization and persistence of STEC in cattle remain unknown, reducing STEC in this host is challenging. In this study, we evaluated a cohort of beef cattle one to eleven years of age to determine the effect of animal age on the prevalence of STEC. During the first year of sample collection, heifers had significantly lower STEC prevalence than cows (37.5% vs. 70%). In the second year of sample collection, STEC prevalence peaked in cows that were two years of age and tended to decrease as animals became older. In addition, by studying a subset of the animals in both years, we observed an increase in STEC prevalence from 40.6% to 53.1% in heifers, whereas cows had a net decrease in STEC prevalence from 71.4% to 61.9%. The results from this study indicate that animal age is a significant factor that influences the prevalence of STEC in cattle. These findings have implications for the development of on-farm mitigation strategies by targeting animals with the highest risk of shedding; it could be possible to reduce pathogen transmission among cattle and prevent zoonotic or foodborne transmission to humans. ß 2014 Elsevier B.V. All rights reserved. * Corresponding author at: Department of Animal Sciences and Emerging Pathogens Institute University of Florida 2055 Mowry Rd Gainesville, FL 32611, United States. Tel.: +1 352 294 5376. E-mail addresses: kcjeong@ufl.edu, hemmos2004@hotmail.com (K.C. Jeong). G Model VETMIC-6851; No. of Pages 7 Please cite this article in press as: Mir, R.A., et al., Association between animal age and the prevalence of Shiga toxin- producing Escherichia coli in a cohort of beef cattle. Vet. Microbiol. (2015), http://dx.doi.org/10.1016/j.vet- mic.2014.12.016 Contents lists available at ScienceDirect Veterinary Microbiology jo u rn al ho m epag e: ww w.els evier.c o m/lo cat e/vetmic http://dx.doi.org/10.1016/j.vetmic.2014.12.016 0378-1135/ß 2014 Elsevier B.V. All rights reserved.