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Encephalitis in Dogs

The term “encephalitis” refers to an inflammation of the brain. However, it also may be accompanied by the inflammation of spinal cord (myelitis), and/or the inflammation of the meninges (meningitis), membranes which cover the brain and spinal cord.

German short-haired pointers, Maltese, and Yorkshire terriers are all found to be predisposed to encephalitis.

Symptoms and Types

Although symptoms may vary depending on the portion of brain affected, they typically appear suddenly and are rapidly progressive. Such symptoms include:

• Fever
• Seizures
• Behavioral changes (e.g., depression)
• Decreased responsiveness
• Head tilt to either side
• Paralysis of face
• Uncoordinated movements or circling
• Unequal size of pupils (anisocoria)
• Smaller sized pinpoint pupils
• Decreased consciousness, which may worsen as disease progresses

Causes

• Idiopathic (unknown cause)
• Immune-mediated disorders
• Postvaccinal complications
• Viral infections (e.g., canine distemper, rabies, parvovirus)
• Bacterial infections (anaerobic and aerobic)
• Fungal infections (e.g., aspergillosis, histoplasmosis, blastomycosis)
• Parasitic infections (e.g., Rocky Mountain spotted fever, ehrlichiosis)
• Foreign bodies

Diagnosis

You will need to give your veterinarian a thorough history of your dog’s health, including the onset and nature of the symptoms, and possible incidents that might have precipitated the unusual behaviors or complications. He or she will then perform a complete physical examination as well as a biochemistry profile, urinalysis, and complete blood count -- the results of which will depend on the underlying cause of the encephalitis.

If your dog has an infection, the complete blood count may show an increased number of white blood cells. Viral infections, meanwhile, may decrease the number of lymphocytes, a type of white cells (also known as lymphopenia). And abnormal reduction in platelets (small cells used in blood clotting) is a good indicator of thrombocytopenia.

To confirm lung involvement and related complications, your veterinarian may employ chest X-rays, while MRIs and CT-scans are used to evaluate the brain involvement in detail. Your veterinarian may also collect a sample of cerebrospinal fluid (CSF), which is then sent to a laboratory for cultures. This is necessary for definitive diagnosis and to determine the severity of the problem. If culture assays are unsuccessful, a brain tissue sample may be necessary to confirm the diagnosis, but this is an expensive procedure.