When does the activity period of encephalitic ticks begin? - briefly
The activity period of encephalitic ticks starts in early spring, usually when temperatures consistently reach 10‑12 °C (around March‑April in most temperate regions). It peaks during the warm months and declines as autumn approaches.
When does the activity period of encephalitic ticks begin? - in detail
The active season of ticks that transmit tick‑borne encephalitis (TBE) starts when ambient temperatures consistently exceed the threshold required for questing behavior, typically around 5 °C (41 °F). In most temperate regions of Europe, this threshold is reached in early spring, often in March or early April, depending on local climate and altitude.
- Southern and low‑lying areas (e.g., the Balkans, parts of Central Europe): questing begins in late February to early March.
- Central Europe and the British Isles: first activity appears in mid‑March to early April.
- Northern latitudes and mountainous zones (Scandinavia, the Alps): tick activity usually commences in late April to May.
- Eastern Europe and Siberia (Ixodes persulcatus zones): onset occurs in April, occasionally delayed until May in more continental climates.
The initial wave consists primarily of nymphs, which become active as soon as temperatures allow. Adult females follow a few weeks later, reaching peak activity from May through July. After the summer peak, activity declines as temperatures drop below the questing threshold and humidity decreases, typically ending in October–November in most regions.
Factors influencing the start of the season include:
- Temperature – sustained daily averages above 5 °C trigger metabolic activity and movement.
- Relative humidity – values above 70 % are needed to prevent desiccation during questing.
- Photoperiod – increasing daylight length stimulates emergence from overwintering sites.
- Microclimate – leaf litter, moss, and low vegetation provide suitable microhabitats that can advance or delay local activity.
Long‑term climate trends have progressively shifted the onset earlier by one to two weeks in many areas, extending the overall period of risk. Surveillance data from public health agencies corroborate this pattern, showing earlier detection of TBE cases corresponding to the advanced tick activity window.
In practice, public health advisories recommend heightened personal protection measures—protective clothing, repellents, and tick checks—starting from the first week of detectable questing activity in each specific region and continuing until the fall decline.