When does a tick transmit encephalitis? - briefly
Transmission generally requires the tick to remain attached for 24–48 hours, allowing the virus to reach its salivary glands. Removing the tick before this period largely prevents encephalitis infection.
When does a tick transmit encephalitis? - in detail
Ticks become vectors for tick‑borne encephalitis (TBE) only after the virus has completed replication within their salivary glands. The virus is acquired when a larval or nymphal tick feeds on an infected host. After ingestion, the virus must cross the midgut barrier, replicate, and migrate to the salivary glands. This process requires a minimum feeding period of approximately 24 hours, although experimental data show that efficient transmission usually occurs after 48 hours of attachment. Transmission risk therefore rises sharply after the first full day of feeding.
Factors that modify the minimum attachment time include:
- Tick species – Ixodes ricinus and Ixodes persulcatus, the primary European and Asian vectors, generally need 24–48 hours; other species may require longer.
- Ambient temperature – Higher temperatures accelerate viral replication, shortening the required feeding duration by several hours.
- Life stage – Nymphs, being smaller, often attach longer than adults, but both stages can transmit after the same developmental threshold.
- Co‑feeding – Simultaneous feeding of infected and uninfected ticks on the same host can transmit virus without the usual replication delay, though this occurs rarely in natural settings.
Consequently, prompt removal of attached ticks within the first 24 hours dramatically reduces the probability of acquiring TBE. After the critical period has elapsed, the probability of virus transmission approaches that of an infected tick’s salivary output, which can reach several hundred virions per minute of feeding.