How do ticks themselves become infected with encephalitis? - briefly
Ticks acquire encephalitic viruses while ingesting infected blood from vertebrate hosts, after which the virus replicates in the midgut and migrates to the salivary glands for onward transmission. Transstadial persistence allows the pathogen to survive through the tick’s developmental stages.
How do ticks themselves become infected with encephalitis? - in detail
Ticks acquire encephalitis viruses primarily during a blood meal from vertebrate hosts that are viremic. The virus enters the tick’s midgut epithelium, replicates, and spreads to secondary tissues, notably the salivary glands, where it is stored until the next feeding event.
Key mechanisms that maintain infection within tick populations include:
- Transstadial persistence – after the initial acquisition, the virus survives through molting stages (larva → nymph → adult), allowing subsequent life stages to transmit the pathogen.
- Transovarial passage – infected females can transmit the virus to their offspring via eggs, establishing infected cohorts without external exposure.
- Co‑feeding transmission – simultaneous feeding of infected and uninfected ticks on the same host permits virus exchange through localized skin pools, even when the host’s systemic viremia is low or absent.
Specific tick species such as Ixodes ricinus in Europe and Ixodes persulcatus in Asia are recognized vectors of tick‑borne encephalitis virus (TBEV), a flavivirus. After ingestion, the virus exploits receptor-mediated endocytosis in gut cells, undergoes replication cycles that increase viral load, and migrates through hemolymph to the salivary glands. Salivary secretion during subsequent feeding delivers the virus into the new host’s bloodstream, initiating infection.
Environmental factors influence acquisition rates. Seasonal host activity, temperature‑dependent tick metabolism, and habitat suitability affect the likelihood of encountering viremic animals. Reservoir hosts—small mammals such as rodents—maintain high-level viremia, providing a consistent source of infection for feeding ticks.
Overall, the combination of direct acquisition from infected vertebrates, internal persistence across developmental stages, vertical transmission to progeny, and localized co‑feeding ensures the continuous circulation of encephalitis viruses within tick populations.