Canine dysautonomia is a degenerative polyneuropathy characterized by neuronal degeneration within the autonomic, somatic, central, peripheral, and/or enteric nervous system, causing multisystemic effects similar, if not identical, to the dysautonomia in horses Equine Dysautonomia Equine dysautonomia (grass sickness) is a disease characterized by degeneration of autonomic neurons in the brain, ganglia, and enteric nervous system. Clinical signs include GI hypomotility... read more 
, cats Feline Dysautonomia The dysautonomias are a group of diseases with strikingly similar clinical and pathologic signs reported in a number of unrelated species, including horses, dogs, cats, rabbits, and hares. The... read more 
, rabbits Leporine Dysautonomia The dysautonomias are a group of diseases with strikingly similar clinical and pathologic signs reported in a number of unrelated species, including horses, dogs, cats, rabbits, and hares. The... read more 
, and hares. Canine dysautonomia was first described in England in 1983, but the disease has not been diagnosed there for many years. Although individual cases have been reported in Scotland, Norway, Belgium, Germany, and Greece, canine dysautonomia is less commonly reported in Europe than in the USA, with higher numbers primarily in the Midwest. In the USA, risk factors were reported to include a rural habitat and spending >50% of the time free outdoors.
Clinical Findings
The most consistent history and physical examination findings are:
acute-onset vomiting
diarrhea
mild obtundation
inappetence
reduced or absent anal tone
absence of pupillary light responses and lacrimal secretion
mydriasis
protrusion of the nictitating membrane
Secondary effects of autonomic dysfunction, such as aspiration pneumonia and lethargy, may develop. Weight loss is often dramatic.
Laboratory findings are nonspecific. Pharmacologic testing of the pupils is probably the best single test to confirm the diagnosis. Dilute pilocarpine (0.05% ophthalmic solution) results in rapid pupillary constriction in dogs with dysautonomia because of supersensitivity of the denervated muscle to cholinergic drugs. The prognosis is grave.
Key Points
Canine dysautonomia is a sporadic, progressive disease of unknown etiology that results in a progressive degeneration of the autonomic nervous system and has a grave prognosis.
For More Information
Hull et al. Canine dysautonomia in a litter of Havanese puppies. J Vet Diagn Invest 2015; 27:627-31
