Grass Sickness
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Description
Equine grass sickness causes a paralysis of the gastro-intestinal tract, by disruption of the autonomic nervous system. The condition may occur acutely, or progress chronically over several weeks, but is fatal in all cases. The aeitology is unknown but an ingested neurotoxin appears to be involved. The neurotoxic is absorbed from the intestinal tract and selectively binds to the autonomic nerve terminals resulting in degeneration and loss of neurons.
Signalment
Cases of Grass sickness are restricted to Northwestern Europe and South America with the highest incidence in the UK, in some parts of Eastern Scotland 1% of horses die annualy from the disease. Young animals, 2-7 years old are predisposed. The disease occurs in warm wet weather with peak incidences in spring and autumn. Affected horses usually live at pasture, those that have moved pasture within the preceeding two months are also at greater risk. In many cases the disease appears to be related to specific pstures or fields with a history of grass sickness affected horses, however it has been reported in animals with none of the usual risk factors.
Diagnosis
Ante-mortm diagnosis of the disease is difficult because changes are confined to the gastro-intestinal tract.
Clinical signs
- Depression
- Abdominal pain, episodes of colic
- Abdominal distension
- Dysphagia
- Inappetence
- Muscular tremors
- Reduced faecal output
- Hypersalivation
- Patchy sweating
Biopsy
A definitive diagnosis is obtained by taking an ileal biopsy and inspecting the intrinsic myenteric plexus. Degenerative lesions and necrosis are seen in the autonomic nerve ganglia and enteric nervous system.
Pathology
- Stomach and small intestine large amounts of contain watery yellow fluid.
- There is an abrupt change in the large intestine, where no fluid is present.
- large intestine has very dry mucoid contents.
- There is an abrupt change in the large intestine, where no fluid is present.
- Stomach and small intestine large amounts of contain watery yellow fluid.
Treatment
There is no effective treatment, prompt euthanasia is indicated in acute and per acute cases, some chronic cases can be managed with intensive nursing care for a limited time period.
Prognosis
The condition is fatal.
References
- Knottenbelt, D.C. A Handbook of Equine Medicine for Final Year Students University of Liverpool
- Rose, R. J. and Hodgson, D. R. (2000) Manual of Equine Practice (Second Edition) Sauders.
| Also known as: | Equine Dysautonomia |