Original Research The Possible Role Mares Play in the Epidemiology of Equine Proliferative Enteropathy Allen E. Page a , Lori Henderson b , Harold F. Stills Jr. c , David W. Horohov a, * a Department of Veterinary Science, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY b Hawk Wing, Tipperary, Ireland c Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, KY article info Article history: Received 22 July 2014 Received in revised form 26 November 2014 Accepted 3 December 2014 Available online 10 December 2014 Keywords: Lawsonia intracellularis Equine Serum Mare ELISA abstract The epidemiology of equine proliferative enteropathy (EPE), caused by the bacterium Lawsonia intracellularis, is poorly characterized. It has been suggested that horse-to- horse transmission of the bacterium may be possible, although no work has examined the role mares may play in the epidemiology of EPE. The goal of this study was to determine whether seropositive mares were more likely to have seropositive foals and whether seropositive mares were more likely to have foals with clinical or subclinical EPE. Serum samples were analyzed using an equine enzyme-linked immunosorbent assay for L. intracellularis–specific antibodies. Over 2 years (2012–2013 and 2013–2014), a total of 197 mare and foal pairs from two central Kentucky Thoroughbred farms with endemic EPE participated in this study. All foals were weaned by the end of October of their respective foaling year. There was no overall effect of mare serologic status on the occurrence of presumptive clinical or subclinical EPE in their offspring. Chi-square analysis determined that those mares with five or more seropositive months through October had a significantly higher number of foals with evidence of exposure to the bacterium between July and January (P ¼ .022). Further, mares with less than five seropositive months through October of their foaling year were found to have foals 2.037 times less likely to be seropositive from July through January than those foals from those with five or more seropositive months through October. Additionally, there appeared to be a protective effect of mares on nursing foals with respect to exposure during the summer months. Ó 2015 Elsevier Inc. All rights reserved. 1. Introduction Lawsonia intracellularis is the causative agent of equine proliferative enteropathy (EPE) [1], a disease typically seen in weanlings and young yearling horses during the fall and early winter months [2]. The most common clinical signs observed with EPE include anorexia, fever, depression, dependent edema, colic, and diarrhea. Antemortem diag- nosis is based on the presence of clinical signs, hypo- proteinemia and hypoalbuminemia, and thickened small intestinal segments detected via abdominal ultrasound. Additional antemortem tests for the detection of L. intra- cellularis infection include detection of the pathogen shed in feces via an L. intracellularis–specific polymerase chain reaction (PCR) assay and analysis of serum samples for bacterium-specific antibodies. With respect to the epidemiology of L. intracellularis,a fecal-oral route of infection is suspected [3], and what little * Corresponding author at: David W. Horohov, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546- 0099. E-mail address: Dwhoro2@uky.edu (D.W. Horohov). Contents lists available at ScienceDirect Journal of Equine Veterinary Science journal homepage: www.j-evs.com 0737-0806/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jevs.2014.12.008 Journal of Equine Veterinary Science 35 (2015) 116–123