Tick Borne Encephalitis

Tick-borne encephalitis, or TBE, is a human viral infectious disease involving the central nervous system.

TBE is caused by the tick-borne encephalitis virus (TBEV), a member of the family Flaviviridae.

Three virus sub-types have been described: European or Western tick-borne encephalitis virus, Siberian tick-borne encephalitis virus, and Far eastern Tick-borne encephalitis virus.

The family Flaviviridae includes several tick-borne viruses affecting humans.

Louping ill virus is also a member of this family; it causes disease primarily in sheep and has been reported as the cause of a TBE-like illness in laboratory workers and persons with contact to sick sheep (e.g., veterinarians, butchers).

In the USA and Russia, another tick-borne flavivirus, Powassan virus, is responsible of encephalitis in human.

Ticks, specifically hard ticks of the family Ixodidae, act as both the vector and reservoir for TBEV.

The main hosts are small rodents, with humans being accidental hosts. Large animals serve as feeding hosts for the ticks, but do not play a role in maintenance of the virus.

The virus can chronically infect ticks and is transmitted both transtadially (from larva to nymph to adult ticks) and transovarially (from adult female tick to eggs).

TBE cases occur in humans most frequently in rural areas and during the highest period of tick activity (between April and November).

Infection also may follow consumption of raw milk from infected goats, sheep, or cows.

Laboratory infections were common before the use of vaccines and availability of biosafety precautions to prevent exposure to infectious aerosols.

Person-to-person transmission has not been reported with the exception of vertical transmission, from an infected mother to fetus.



Symptoms are nonspecific and may include fever, malaise, anorexia, muscle aches, headache, nausea, and/or vomiting.

After about 8 days of remission, a second phase of disease occurs in 20% to 30% of patients.

These patients may experience a clinical illness that involves the central nervous system with symptoms of meningitis (e.g., fever, headache, and a stiff neck), encephalitis (e.g., drowsiness, confusion, sensory disturbances, and/or motor abnormalities such as paralysis), or meningoencephalitis.

The convalescent or recovery period can be long and the incidence of sequelae may vary between 30% and 60%, with long-term or even permanent neurologic symptoms.

Neuropsychiatric sequelae have been reported in 10-20% of patients. Source


During the first phase of the disease, the most common laboratory abnormalities are a low white blood cell count (leukopenia) and a low platelet count (thrombocytopenia). Liver enzymes in the serum may also be mildly elevated.

After the onset of neurologic disease during the second phase, an increase in the number of white blood cells in the blood and the cerebrospinal fluid (CSF) is usually found.

Virus can be isolated from the blood during the first phase of the disease.

Laboratory diagnosis usually depends on detection of specific IgM in either blood or CSF, usually appearing later, during the second phase of the disease. Source


There is no specific drug therapy for TBE.

Meningitis, encephalitis, or meningoencephalitis requires hospitalization and supportive care based on syndrome severity.

Anti-inflammatory drugs, such as corticosteroids, may be considered under specific circumstances for symptomatic relief. Intubation and ventilator support may be necessary. Source


Dr. Daniel Cameron


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Last Update- January 2020

Lucy Barnes