Contents lists available at ScienceDirect Virus Research journal homepage: www.elsevier.com/locate/virusres Short communication First demonstration of equid gammaherpesviruses within the gastric mucosal epithelium of horses Matthew R. Pennington a , Brieuc G.A. Cossic b , Gillian A. Perkins c , Carol Duffy d , Gerald E. Duhamel b , Gerlinde R. Van de Walle a, ⁎ a Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA b Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA c Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA d Department of Biological Sciences, College of Arts and Sciences, University of Alabama, Tuscaloosa, AL, USA ARTICLE INFO Keywords: Equid Gammaherpesvirus Gastrointestinal tract Equine gastric ulcer syndrome ABSTRACT Horses commonly develop gastric mucosal ulcers, similar to humans, a condition known as equine gastric ulcer syndrome (EGUS) that can lead to poor performance and lost training time and care expenses. Unlike humans, however, an infectious bacterial cause of ulcers has not been conclusively identified. Herpesviruses, while well- established causative agents of diseases such as cold sores, genital lesions, and certain types of cancer, have also been implicated in the development of a subset of gastric ulcers in humans. The presence of equid herpesviruses in the gastrointestinal tract and their potential contribution to EGUS has not been evaluated. Here, we provide the first evidence of equid gammaherpesviruses 2 and 5 (EHV-2 and -5) within the epithelium of the gastric mucosa of horses. These viruses were initially detected by a nested PCR screen of gastric tissue samples obtained from client- and university-owned horses with and without ulcers; however, no association with EGUS was found in this limited sample set. We then validated a highly sensitive in situ hybridization (ISH) assay and used this assay to characterize the distribution of these viruses in necropsy gastric tissue samples from five racehorses. Analyses revealed frequent EHV-2 and EHV-5 co-infections within the gastric mucosal epithelium, regardless of the ulcer status. These results are the first to demonstrate the presence of equid gammaherpesviruses in the gastric mucosa of horses and warrants further investigation to determine the contribution of these viruses to the development of EGUS and/or other gastrointestinal diseases. Equine gastric ulcer syndrome (EGUS) in horses is a highly pre- valent and painful condition that results in lost training time and medical expenses. EGUS is characterized by ulceration primarily of the non-glandular, squamous region of the stomach, but can also affect the glandular region and proximal duodenum. In humans, ulcers form fol- lowing a break in the mucosae of the stomach, most commonly due to infection with Helicobacter pylori or administration of non-steroidal anti-inflammatory drugs (NSAID), and subsequent mucosal damage induced by stomach acid and pepsin (Graham, 2014; Penston, 1993). In contrast, the etiology of EGUS is poorly defined, but typically occurs during periods of high stress, such as racing, intense training, en- durance racing/riding, extended travel, late pregnancy, and weaning of foals (Bell et al., 2007b; Videla and Andrews, 2009). As in humans, Helicobacter has been postulated as a cause of EGUS. In 2007, Moyaert et al. identified a novel bacterium species, named Helicobacter equorum, in fecal samples of 2 horses, and Contreras et al. subsequently reported the presence of Helicobacter-like DNA in gastric ulcers of 2 out of 7 horses (Contreras et al., 2007; Moyaert et al., 2007). However, several studies investigating the equine gastric mucosal microbiota failed to identify Helicobacter spp. in gastric ulcer biopsies, suggesting that He- licobacter may not be an important inducer of EGUS (Dong et al., 2016; Husted et al., 2010; Perkins et al., 2012). Interestingly, herpesviruses have been implicated in the formation of some gastric ulcers in humans, based on (i) the observation of in- tranuclear inclusion bodies in the gastric epithelium of patients with peptic ulcers (Knyvett, 1967; Neumann, 1967), (ii) the detection of http://dx.doi.org/10.1016/j.virusres.2017.09.002 Received 29 June 2017; Received in revised form 31 August 2017; Accepted 1 September 2017 ⁎ Corresponding author at: Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14850, USA. E-mail address: grv23@cornell.edu (G.R. Van de Walle). Abbreviations: EGGUS, equine glandular gastric ulcer syndrome; EGUS, equine gastric ulcer syndrome; EHV-1, equid alphaherpesvirus 1; EHV-2, equid gammaherpesvirus 2; EHV-3, equid alphaherpesvirus 3; EHV-4, equid alphaherpesvirus 4; EHV-5, equid gammaherpesvirus 5; EMPF, equine multinodular pulmonary fibrosis; ESGUS, equine squamous gastric ulcer syndrome; HHV-1, human alphaherpesvirus 1, Herpes simplex virus 1; HHV-3, human alphaherpesvirus 3 Varicella-Zoster virus; HHV-4, human gammaherpesvirus 4, Epstein-Barr virus; ISH, in situ hybridization; NSAID, non-steroidal anti-inflammatory drugs Virus Research 242 (2017) 30–36 0168-1702/ © 2017 Elsevier B.V. All rights reserved. MARK