Page 186 - TBE_Book_V2_2019

Chapter 10

Diagnosis

Gerhard Dobler

Key Points

• TBE appears with non-characteristic clinical symptoms, which cannot be distinguished from oth-
er forms of viral encephalitis or other diseases.

• Cerebrospinal fluid and neuro-imaging may give some evidence of TBE, but ultimately cannot
confirm the diagnosis.
• Thus, proving the diagnosis “TBE” necessarily requires confirmation of TBEV-infection by detec-
tion of the virus or by demonstration of specific antibodies from serum and/or cerebrospinal
fluid.

• During the phase of clinic symptoms from the CNS, the TBEV can only rarely be detected in the
cerebrospinal fluid of patients.
• Most routinely used serological tests for diagnosing TBE (ELISA, HI, IFA) show cross reactions
resulting from either Infection with other flaviviruses or with other flavivirus vaccines.

Clinical confirmation of suspected TBEV infection

Tick-borne encephalitis (TBE) manifests as a The most common method of detecting TBEV
non-specific disease with symptoms of a infection nowadays is via serological assays,
febrile, influenza-like illness and, in some which have developed from complement
cases, an inflammatory infection of the central fixation or hemagglutination inhibition tests
nervous system (CNS) that follows a few days through to modern immuno-globulin (Ig)-
later. Due to the lack of specific symptoms, a specific tests such as ELISAs and immuno-
definitive confirmation of the diagnosis fluorescence (IF) assays.
requires taking the history of the patient with
regard to a possible tick bite or ingestion of Understanding of the pathogenesis and
unpasteurized milk in a known or suspected immunology of TBEV infection is essential for
endemic area, plus a positive result from a the selection and interpretation of appropri-
classical virological test that confirms TBEV- ate diagnostic tests (Figure 1). For example,
infection either directly by the detection of the European subtype of TBEV often induces a
virus or indirectly via detection of specific anti- biphasic clinical course, whereas a mono-
1
virus antibodies. Prior to the introduction of phasic course may be more prominent in
molecular detection technologies such as those infected with the Far Eastern subtype or
2
polymerase chain reaction (PCR), the only Siberian subtype. Following a bite from an
technique available to detect TBEV infection infected tick, the virus is assumed to replicate
was virus isolation, but this is rarely used locally within antigen-presenting cells and
today. then subsequently within nearby lymph
nodes. After replicating within the lymph

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