E35 - Myenteric Ganglionitis Underlying Intestinal Motor Dysfunction in 3 Horses Diagnosed with Equine Herpesvirus 1 post-mortem

Abstract: Background: Myenteric ganglionitis (MG) represents an infiltrative neuropathy of the enteric nervous system leading to impaired gastrointestinal motility, frequently associated with long term poor prognosis in horses. Equine herpesvirus 1 (EHV-1) has been detected in the enteric nervous system following cell-associated viremia and was suggested as a potential underlying cause of MG. In other species, herpesvirus myenteric plexus infection triggers inflammatory cell recruitment with secondary neurodegeneration and development of peristalsis abnormalities.



Objective: To illustrate the clinical course of three cases treated for recurrent colic, diagnosed with MG and EHV-1 infection on post-mortem exam.



Cases description and outcome: Three thoroughbred geldings, aged between 4 and 6 years old, were treated for recurrent colic. Clinical signs and disease progression varied despite medical therapy. Two horses were euthanized following acute intestinal rupture. One horse underwent exploratory laparotomy, and after no significant abnormalities were found and continuous clinical deterioration post-surgery, the horse was humanely destroyed. Post-mortem examination revealed multifocal MG of diverse intestinal segments in all cases, characterized by a lymphocytic inflammatory infiltrate and myenteric plexus neuronal degeneration. Colon samples, from all cases, were RT-PCR positive for EHV-1 wild-type (non-neuropathogenic). EHV-1 immunohistochemistry results were equivocal in all three cases.



Clinical importance: To our knowledge, this is the first case series reporting the concomitant diagnosis of MG and EHV-1 infection in horses. Further studies are required to investigate underlying pathophysiological mechanisms that relate the occurrence of myenteric plexus inflammation/neurodegeneration and equine herpesvirus infection.