Tick-borne encephalitis (TBE) is a viral infection that can affect the central nervous system. Making the diagnosis can be challenging.
Pathogen: TBEV (tick-borne encephalitis virus)
Distribution: central Europe, Siberia, Far East
Diagnostic considerations:
(1) exposure in a region where TBE occurs
(2) evidence of CNS involvement (meningitis, meningoencephalitis, etc)
(3) elevated CSF white blood cell count (neutrophils early, lymphocytes later)
(4) serologic response with IgM and IgG antibodies
(5) molecular methods (such as PCR)
(6) exclusion of alternative diagnosis
Challenges to diagnosis:
(1) patients without CNS involvement
(2) normal CSF white blood cell count (absence of pleocytosis)
(3) status post vaccination to TBEV
(4) status post vaccination to other flaviviruses (yellow fever, Japanese encephalitis)
(5) status post infection with other flaviviruses (dengue, West Nile, etc)
(6) false positive PCR
Intrathecal production of IgM and IgG antibodies against TBE is diagnostic and is almost always present by day 10. This can be helpful in the diagnosis of a patient who has been vaccinated.
