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

The research study investigates a case where a trotter horse experienced chronic intestinal pseudo-obstruction (CIP) linked to an infection caused by the equine herpesvirus (EHV)-1. It establishes a potential correlation between EHV-1 infection and enteric ganglionitis.

Introduction and Findings

• The study revolves around a 7-year-old male trotter horse which was suffering from recurrent colic – a severe often fluctuating pain in the abdomen.
• The horse exhibited symptoms indicative of chronic intestinal pseudo-obstruction (CIP), a disorder characterized by persistent issues with intestinal blockage sans any physical obstruction.
• During surgery, an obstruction was found in the descending portion of the horse’s colon, which was related to a severe atrophy (degeneration) of the right dorsal colon.
• The horse was euthanized due to this condition and a subsequent necropsy (autopsy conducted on animals) revealed diffuse enteric ganglionitis, an inflammation of neuronal clusters in the gut wall.

Identification of Pathological Changes

• The necropsy examination found a widespread infiltration of CD3(+) T lymphocytes and plasma cells, which are immune system cells potentially indicating an immune response to a disease or infection.
• Noticeable were the significant reduction in the count of myenteric ganglia and normal ganglion cells across all levels of the horse’s intestinal tract. Myenteric ganglia play a significant part in controlling the muscular tension and reflexes of the gut.
• The researchers also found neurons undergoing chromatolysis (degeneration) or becoming necrotic (dying), coupled with an increase in connective tissue surrounding the ganglia, indicative of some pathological changes.

Immunohistochemical Studies

• Immunohistochemical studies examining the expression of various cellular proteins were conducted on samples from the horse’s right dorsal colon.
• These studies found a minor decrease in expression of neuron-specific enolase, a substance indicative of neurons’ presence and health, and a moderate rise in expression of S100 and glial fibrillary acidic protein, often associated with neurological damage.

Aetiological Association with EHV-1

• A semi-nested polymerase chain reaction was employed to look for the presence of equine herpesvirus (EHV)-1 in the horse’s gut tissue. The results were positive, coupled with positive immuno-labelling, indicating the horse was indeed infected by EHV-1.
• This finding suggests an aetiological relationship between the horse’s EHV-1 infection and enteric ganglionitis, indicating that the EHV-1 infection may be a direct cause or a contributing factor to the condition.