Extensive myenteric ganglionitis in a case of equine chronic intestinal pseudo-obstruction associated with EHV-1 infection.

A 7-year-old male trotter horse with a history of recurrent colic displayed clinical findings consistent with chronic intestinal pseudo-obstruction (CIP). At laparotomy, an impaction of the descending colon associated with marked atrophy of the right dorsal colon was found. The horse was humanely destroyed and tissues collected at necropsy examination revealed diffuse enteric ganglionitis comprising an infiltrate of CD3(+) T lymphocytes and plasma cells. At all levels of the intestinal tract the number of myenteric ganglia and of normal ganglion cells was decreased significantly. There were chromatolytic or necrotic neurons and the amount of connective tissue surrounding ganglia was increased. Immunohistochemical studies demonstrated slightly reduced expression of neuron-specific enolase and a moderate increase in expression of S100 and glial fibrillary acidic protein in a sample of right dorsal colon taken during the necropsy examination compared with a biopsy sample taken from the same location. Immunolabelling and semi-nested polymerase chain reaction for equine herpesvirus (EHV)-1 performed on the gut were positive, supporting an aetiological relationship between EHV-1 infection and the enteric ganglionitis.