Where do ticks get infected with encephalitis? - briefly
Ticks acquire encephalitis viruses while feeding on infected wildlife—typically rodents, hares, and certain bird species. Transmission is concentrated in habitats where these hosts thrive, such as forests, grasslands, and shrub‑dominated areas within endemic regions.
Where do ticks get infected with encephalitis? - in detail
Ticks acquire the virus that causes tick‑borne encephalitis (TBE) while feeding on infected vertebrate hosts. The primary reservoirs are small mammals—mainly rodents such as bank voles (Myodes glareolus) and yellow‑necked mice (Apodemus flavicollis)—which maintain the virus in natural foci. Adult and nymphal ticks attach to these hosts during their blood meals, ingesting the virus from the host’s bloodstream.
Geographic distribution of these foci determines where infected ticks are found. The virus persists in:
- Forested areas of Central, Eastern, and Northern Europe, including the Baltic states, Scandinavia, and parts of Russia.
- Mountain valleys and mixed woodlands of Central Asia and the Caucasus.
- Suburban woodlands and parklands where rodent populations thrive.
Within each focus, the virus circulates in a cycle that involves:
- Rodent host – sustains viral replication; infected animals often show no clinical signs.
- Larval or nymphal tick – acquires virus during its first or second blood meal from the rodent.
- Maturation – infected nymph develops into an adult, retaining the virus in its salivary glands.
- Subsequent feeding – adult tick can transmit the virus to larger mammals (including humans) during later blood meals.
Environmental conditions that favor high rodent density—such as abundant mast production, mild winters, and humid microclimates—enhance the likelihood that questing ticks become infected. Human exposure increases in regions where people engage in outdoor activities (hiking, forestry work, mushroom picking) within these habitats.
In summary, ticks become carriers of the encephalitis‑causing virus in natural rodent‑tick cycles that are confined to specific forested and mountainous ecosystems across Europe and parts of Asia. The presence of competent reservoir hosts and suitable climatic conditions defines the locations where infected ticks are encountered.