Tick Born Viral Encephalitis (Far Eastern, Central European, Powassan and Louping Ill Encephalitis)

Tick borne viral encephalitis is a viral infection of the central nervous system caused by members of the flavivirus family: Far Eastern tick borne encephalitis virus, Central European tick borne encephalitis virus, Powassan encephalitis virus and Louping Ill encephalitis virus.

The viruses are harbored in sheep, deer, rodents and birds. It is transmitted to humans through the bite of ticks that feed on the animals and birds. Symptoms include fever, headache, vomiting and changes in levels of consciousness.

What sets this group of encephalitis infections apart are the serious permanent neurological effects of paralysis that can follow.

Where does it occur?

Far Eastern encephalitis (FE): Western Siberia

Central European encephalitis (CE): Central Europe, Scandinavia, England

Powassan Encephalitis (PE): Canada, USA, Russia

Louping Ill Encephalitis (LE): England, Ireland

How is it transmitted?

FE, PE and LE are commonly contracted through the bite of infected ticks. Central European tick borne encephalitis in addition can also be contacted by ingesting raw milk from infected cows.

Is it contagious from person to person?

It is not contagious from person to person.

What is the risk for travelers?

Risk for travelers is usually low, prolonged outdoor activities with chance for tick bites increases one’s risk.

How soon after exposure will one develop symptoms?

Symptoms usually develop within 1-2 weeks of exposure.

What are the signs and symptoms?

FE: One experiences sudden onset of fever, headache, discomfort at exposure to bright lights, nausea and vomiting. This is followed by neurologic symptoms of change in consciousness, unsteady gait, seizures, etc. Many soon develop one sided paralysis of upper limbs, face and neck. There is a 20% mortality and 60% are left with permanent neurological deficits.

CE, LE, PE: Symptoms caused by these viruses have 2 phases. The 1st phase is characterized by flu-like illness of fever, chills, body aches and vomiting. After symptoms resolve for a few days; there is a relapse with fever, headache, irritability, changes in level of consciousness followed by paralysis of upper limbs, face and neck. In general neurologic symptoms are less severe than in Far Eastern encephalitis.

Is there any treatment?

Treatment is supportive.

Are there any lab tests to diagnose illness?

Antibody tests are available to be performed on blood and spinal fluid.

What preventive measures can be taken?

Vaccines are available in Europe only. Take insect safety precautions and avoid drinking unpasteurized milk.

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