Complete clinical recovery of a pony with histologically confirmed chronic grass sickness

Diagnostic and Clinical Course of Small Colon Recurrent Impaction Associated with Severe Myenteric Ganglionopathy in A Mare

A 10-year-old Koninklijk Warmbloed Paardenstamboek Nederland (KWPN, Netherlands-based organization for registration of the Dutch Warmblood horses) mare was evaluated three times over four months because of recurrent colic. At every referral, a physical examination revealed a small colon impaction, which partially responded to food deprivation and oral administration of water and magnesium sulphate. Due to the recurrent nature of the small colon impaction, several differential diagnoses were considered: inflammatory bowel disease (IBD), chronic salmonellosis and myenteric ganglionopathies. At first admission, an exploratory laparotomy was proposed, but the owner declined. On the second hospitalisation, the mare underwent a standing exploratory laparoscopy, but no abnormality related to the small colon was detected and resolved with a soap-based enema. At the third hospitalisation, the owner agreed to the exploratory laparotomy, which allowed surgical biopsies of the caecum and the large and small colon. Lymphomonocytic enteritis and mild myenteric ganglionitis were diagnosed. After laparotomy, the mare regularly fed and defecated, but a few days later, tachycardia, fever and abundant gastric reflux occurred. As the clinical condition rapidly deteriorated, the owner elected for euthanasia. A post-mortem histological examination showed severe chronic lymphocytic enterocolitis and typhlitis associated with the marked depletion of myenteric ganglion bodies. Small colon impaction is a very common disorder of the small colon in horses. In the presence of myenteric ganglionopathies, this case proposes the controversial matter of primary or secondary disorders of enteric neuromuscular function as the base of repeated small colon impactions of the horse. In this mare, recurrent small colon impaction was considered secondary to severe myenteric ganglionopathy associated with chronic intestinal pseudo-obstruction.

Observations on the Interstitial Cells of Cajal and Neurons in a Recovered Case of Equine Dysautonomia (Grass Sickness)

This paper describes the histopathological and immunohistochemical changes in the central, autonomic and enteric nervous systems in a well-documented case of equine dysautonomia (ED), after the animal had recovered without significant residual clinical signs. Evidence of neuronal degeneration, such as neuronal chromatolysis, glial scars or a decrease in density of neurons, was not observed in the midbrain, pons, medulla oblongata or spinal cord, including the nuclei of cranial nerves III, V, VII, X and XII. In addition, no evidence of muscle denervation or re-innervation, such as group atrophy of clusters of cells or grouping of cells of similar size in the triceps muscle, was observed. These findings support the hypothesis that the chromatolytic motor neurons may not progress to cell death in ED. The autonomic ganglia showed evidence of previous neuronal loss. In the myenteric and submucosal plexuses of the ileum there was significant loss of enteric neurons. However, in the ileum, a continuous network of interstitial cells of Cajal (ICC) was observed by means of immunohistochemical techniques. It is possible that recovery without significant residual clinical signs was associated with lack of damage to, or more likely recovery of, the ICC, which have a pacemaker function in the intestinal tract.