Where did encephalitis ticks appear from? - briefly
The primary vectors, Ixodes ricinus and Ixodes persulcatus, are native to forested zones of Central and Eastern Europe and northern Asia, where tick‑borne encephalitis was first documented. These regions remain the main endemic areas.
Where did encephalitis ticks appear from? - in detail
Tick‑borne encephalitis is transmitted primarily by two hard‑tick species, «Ixodes ricinus» and «Ixodes persulcatus». Both belong to a lineage that evolved within the temperate and boreal forests of the Eurasian continent. Fossil and genetic evidence places the divergence of these vectors several million years ago, coinciding with the expansion of mixed‑leaf and coniferous woodlands that supported their preferred hosts—small rodents such as voles and mice.
Historical records locate the first recognized foci of the disease in the forested regions of western Russia and the Baltic states during the early 1900s. Surveillance data from that period describe a stable enzootic cycle in which larvae and nymphs acquire the virus from infected rodents, later transmitting it to humans during the questing stage of the tick’s life cycle.
The current distribution reflects a combination of natural and anthropogenic factors:
- Climate warming extends the seasonal activity and geographic range of both tick species, enabling colonization of higher latitudes and elevations.
- Changes in land use, including afforestation and rewilding projects, increase suitable habitat for rodent reservoirs and their ectoparasites.
- Expansion of recreational outdoor activities raises human exposure to questing ticks in previously low‑risk areas.
These dynamics have produced a noticeable northward shift of TBE‑vector populations into Scandinavia, the United Kingdom, and parts of Central Europe where the disease was once rare. Continuous monitoring of tick density, virus prevalence, and environmental variables is essential for predicting further emergence and guiding public‑health interventions.