3.4 NEUROLOGICAL DISEASES OF OLD AGE CHRONIC 'OLD DOG' ENCEPHALITIS

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Canine distemper is most prevalent in young dogs, but chronic 'old dog' encephalitis is the neurological manifestation of canine distemper virus (CDV) infection that is seen in adult dogs which have survived the acute infection. Dogs developing this condition are usually over 6 years of age and have serological evidence of systemic immunity.

The neurological signs (see Table 3.4) may occur without previous evidence of systemic disease and are usually progressive and irreversible (Greene and Appel 1990; Skerritt 1989). The involuntary muscle twitching (myoclonus) is typical of CDV infection.


CSF examination for increased protein and increased lymphocyte count may be helpful in diagnosing dogs exhibiting neurological signs.

Histologically there is perivascular lymphoplasmacytic infiltration in areas of demyelination and neuronal degeneration which may progress to

sclerosing panencephalitis in more chronic cases. Canine distemper virus inclusion bodies are present in epithelial and other cells but their sigis not clear (Greene & Appel 1990).

Distemper can occur after stress, during concurrent illness or in immunesuppressed vaccinated dogs. Although vaccination with modified live CDV may confer long-term active immunity to some individuals, most manufacturers recommend booster vaccinations at 1-2 year intervals to ensure adequate ongoing protection.

The long-term prognosis is poor for most cases and, although some authors advocate a period of 1-2 weeks supportive therapy, euthanasia is usually the eventual outcome.


Seizures
Metabolic Encephalopathies
Peripheral Polyneuropathies
Neoplasia
Reticulosis
Spinal Disease
Vestibular Disease