Clinical and biochemical features of grass sickness (equine dysautonomia)

Abstract

Summary An attempt has been made to assess the diagnostic value of clinical features seen at initial examination of horses with grass sickness, colic cases and cases submitted as possible grass sickness but diagnosed subsequently as some other condition. There appears to be no single pathognomonic sign for grass sickness. A range of signs has been associated with grass sickness but these are of value only when related to the length of illness and the history. Biochemical tests related to intestinal tissue damage, stress and dehydration were evaluated and most were found to be of value in diagnosing acute grass sickness. No evidence was found relating selected mineral or vitamin deficiencies to grass sickness, nor were protein changes specific. A marked fall in glutathione peroxidase values was associated with grazing rather than disease.

Small intestine and small colon neuropathy in equine dysautonomia (grass sickness)

“…Our results only partially confirm this view. Despite the distinguishable clinical differences between acute, subacute and chronic dysautonomia (see Doxey et al, 1991), associated histological differences were not seen in the ileum. In all types of dysautonomia, the damage in the ileum was so extensive and severe, especially in the submucosal plexus, that the function of the distal small intestine must have been badly affected.…”

“…The ideas so far put forward have to be considered against the fact that many adult animals which have probably been exposed to the 'toxin' appear to be unaffected by the disease; very young foals appear to be unaffected and stress appears to be a precipitating feature in some cases at least (Doxey et al, 1991). Whether thege phenomena can be related to neuronal function remains to be seen, but some of the coeliacomesenteric ganglia neurons and possibly those in the jejuna!…”

“…The clinical picture of equine dysautonomia is well documented and has not changed over a period of 70 years (Pool, 1927;Doxey et al, 1991). Obel (1955) gave the first description of the histologically detectable changes which occur in equine dysautonomia.…”

Are the Equine Motor Neuron Disease (EMND) and the Grass Sickness of the horse different manifestations of the same underlying disease?

“…Unrer unseren Verhältnissen ist jedenfalls nicht zu erwarten, dass bei GS ein primärer Vitamin E-Mangel vorliegen könnte, da zur Zeft des \ü7eide-gangs die Versorgung mit Tokopherol gewährleistet sein dürfte. Doxey et al (1991) haben im übrigen in Schottland bei Graskrankheit normale Vitamin E-\ü7erte gefunden.…”

Neurodegenerative Disorders

“…Serum concentrations of numerous acute phase protein, including α-2 macroglobulin, ceruloplasmin, haptoglobin, and orosomucoid, are high, but such assays are not readily available. 88 ILEAL BIOPSY A full-thickness ileal biopsy is obtained during exploratory celiotomy and is examined histologically for characteristic histologic changes to nerve plexi. 74 This technique is highly sensitive and specific for diagnosis of grass sickness.…”