SMALL-INTESTINE AND SMALL COLON NEUROPATHY IN EQUINE DYSAUTONOMIA (GRASS SICKNESS)

The number of neurons in the coeliacomesenteric ganglia and the myente ric and submucosal plexuses of the jejunum, ileum and small colon, and the pathological changes induced in them, were studied in various typ es of equine dysautonomia. In all forms of dysautonomia, severe and ex tensive neuron loss and damage occurred in the ileum. In acute and sub acute dysautonomia, jejunal neuron loss and damage were severe, but in chronic cases significantly less loss or damage occurred. The damage followed the same pattern in the small colon but it was always less ob vious than in the jejunum. The distribution of the damage was uniform within a segment of the intestine. In fatal cases of dysautonomia, the clinical severity and duration of illness seems, in most instances to be related to the amount of neuronal disruption occurring in the jeju num. Severe disruption results in acute/subacate dysautonomia, while m ilder damage leads to the chronic form. No case of dysautonomia was en countered in which enteric neuron loss and damage occurred without sig nificant neuronal disruption also occurring in the coeliacomesenteric ganglia. Ileal neuronal damage and loss are not invariably worse than that in the jejunum and the possible reasons for this, together with t he relationship between neuronal damage and possible causes of dysauto nomia, are discussed.