Research Article Enteric Pathogens and Coinfections in Foals with and without Diarrhea Giovane Olivo, 1 Thays Mizuki Lucas, 2 Alexandre Secorun Borges, 1 Rodrigo Otávio Silveira Silva, 3 Francisco Carlos Faria Lobato, 3 Amanda Keller Siqueira, 4 Domingos da Silva Leite, 4 Paulo Eduardo Brandão, 5 Fábio Gregori, 5 José Paes de Oliveira-Filho, 1 Shinji Takai, 6 and Márcio Garcia Ribeiro 2 1 Department of Veterinary Clinical Sciences, Universidade Estadual Paulista (UNESP), Botucatu, SP, Brazil 2 Department of Veterinary Hygiene and Public Health, Universidade Estadual Paulista (UNESP), Botucatu, SP, Brazil 3 Department of Preventive Veterinary Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, MG, Brazil 4 Department of Genetics, Evolution and Bioagents, Campinas State University (Unicamp), Campinas, SP, Brazil 5 Department of Preventive Veterinary Medicine, University of S˜ ao Paulo, S˜ ao Paulo, SP, Brazil 6 Department of Animal Hygiene, Kitasato University, Towada, Aomori, Japan Correspondence should be addressed to M´ arcio Garcia Ribeiro; mgribeiro@fmvz.unesp.br Received 15 September 2016; Accepted 23 November 2016 Academic Editor: Eric N. Villegas Copyright © 2016 Giovane Olivo et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Diarrhea is a major clinical problem afecting foals up to 3 months of age. Te aim of this study was to identify enteric microorganisms involved in monoinfections and coinfections and the associated virulence factors in healthy and diarrheic foals. Diarrheic (D) ( = 56) and nondiarrheic (ND) foals ( = 60) up to three months of age were studied. Fecal samples were analyzed for identifcation of infectious agents (microbiological culturing, molecular techniques, and microscopic analyses). Escherichia coli fmH (30% versus 25%), Salmonella spp. (25% versus 7%), Strongyloides westeri (25% versus 25%), Clostridium perfringens type A (21% versus 10%), E. coli ag43 (20% versus 35%), Strongylus (11% versus 18%), and vapA-positive Rhodococcus equi (5% versus 2%) were the most frequent enteric pathogens detected in D and ND foals, respectively. Te frequency of toxin A-positive C. perfringens was signifcantly increased in the D ( = 0.033) compared with the ND animals. R. equi strains harboring virulent plasmids were also identifed (VapA 85-kb type I and VapA 87-kb type I) in D and ND foals. Coinfections were observed in 46% of the D and 33% of the ND foals. Our results demonstrate the great diversity of enteric pathogens, virulence factors, and coinfections involved in enteric infections of foals. 1. Introduction Diarrhea is one the most common causes of mortality of neonatal foals, which results in economic losses worldwide [1, 2]. Until 6 months of life, up to 20% of foals have been reported to sufer from diarrhea caused by infectious agents [3]. Te etiology of diarrhea in neonatal foals is complex and involves infectious agents, management, and facilities, as well as nutritional, environmental, and physiological conditions [3–5]. Infectious causes of foal diarrhea predominantly include bacteria, viruses, and parasitic agents [5–7]. Some studies of diarrhea in neonatal foals have focused on only one pathogen [2, 8–11] although it is usually caused by diverse combinations of enteric infections [1, 5, 7, 12, 13]. Te understanding of the prevalence and complexity of major pathogens associated with enteric infections in neonatal foals is limited [14]. Com- prehensive studies have highlighted the impacts of enteric coinfections in foals with diarrhea and have identifed major virulence factors of some pathogens in these infections [1, 5, 7, 13]. However, few studies have evaluated the normal microbial population of the equine intestine, particularly in foals [15–17]. Nondiarrheic foals have been suggested to be potential reservoirs of enteric pathogens, including agents with zoonotic potential [13, 18]. Te aim of this study was to identify enteric microorganisms involved in monoinfections Hindawi Publishing Corporation BioMed Research International Volume 2016, Article ID 1512690, 12 pages http://dx.doi.org/10.1155/2016/1512690