When should a test for tick-borne encephalitis be taken after a tick bite? - briefly
If the individual has not been vaccinated, serologic testing should be performed roughly 2–3 weeks after the bite, or earlier if fever, headache, or neurological signs appear.
When should a test for tick-borne encephalitis be taken after a tick bite? - in detail
Testing for tick‑borne encephalitis (TBE) after a tick bite must align with the pathogen’s incubation dynamics and the diagnostic methods available.
The virus typically appears in the bloodstream within the first week after attachment. Molecular detection (PCR) is most reliable between days 5 and 10 post‑exposure, when viral RNA can still be identified in blood or cerebrospinal fluid. After this period, viral load declines and PCR sensitivity drops sharply.
Serological assays become informative later. Specific IgM antibodies usually emerge 7–14 days after infection and rise to detectable levels by day 14–21. IgG antibodies appear after 2–3 weeks and persist long term. Therefore, a first serology sample should be drawn no earlier than day 14 to avoid false‑negative results. If the initial test is negative but clinical suspicion remains, a second sample collected 7–10 days later can demonstrate seroconversion.
Practical schedule for a person with a confirmed tick attachment:
- Day 0–4: Observe the bite site; no laboratory test recommended.
- Day 5–10: Consider PCR if early neurological symptoms develop (headache, fever, meningismus). Otherwise, defer testing.
- Day 14–21: Obtain a serum sample for TBE‑specific IgM/IgG. This is the standard window for initial serology.
- Day 21–28: If the first serology is negative and symptoms persist, repeat serology to detect rising antibody titers.
Additional considerations:
- Vaccination status: Fully immunised individuals may show a rapid IgG response; a single IgM positive result is more indicative of recent infection.
- Symptom onset: Testing should be prompted by fever, headache, or neurological signs rather than by the bite alone.
- Geographical risk: In endemic regions, clinicians may lower the threshold for early PCR testing even in the absence of symptoms.
In summary, molecular testing is appropriate within the first 10 days post‑exposure, while serological assessment is most reliable from the second week onward, with a repeat sample if the initial result is inconclusive.