Where does the encephalitis that ticks carry come from? - briefly
«Tick‑borne encephalitis virus» is maintained in wildlife reservoirs—primarily small mammals such as rodents—that infect feeding ticks, and the infected ticks serve as the vector to humans. The natural transmission cycle occurs in forested and grassland areas throughout Europe and Asia.
Where does the encephalitis that ticks carry come from? - in detail
Tick‑borne encephalitis (TBE) is caused by the tick‑borne encephalitis virus (TBEV), a flavivirus maintained in a natural cycle that involves arthropod vectors and vertebrate reservoirs.
Small mammals, principally rodents such as the bank vole (Myodes glareolus) and the common wood mouse (Apodemus sylvaticus), serve as the primary amplifying hosts. These animals develop a transient viremia sufficient for virus acquisition by feeding ticks. Certain ground‑feeding birds and shrews can also participate in the cycle, providing additional reservoirs in some regions.
Ixodes ricinus in Western Europe and Ixodes persulcatus in Eastern Europe and Siberia are the main vector species. The virus persists within ticks through several mechanisms:
- transstadial transmission, allowing infected larvae to retain the virus as they molt to nymphs and adults;
- transovarial transmission, passing the pathogen from adult females to their offspring;
- co‑feeding, whereby uninfected ticks acquire the virus from neighboring infected ticks while feeding on the same host, even in the absence of detectable host viremia.
Human infection originates almost exclusively from the bite of an infected nymph or adult tick during the questing period. In rare cases, consumption of unpasteurised dairy products from livestock that have ingested infected ticks can transmit the virus.
The geographic range of the disease mirrors the distribution of the competent tick species and suitable habitats for reservoir hosts, encompassing temperate forested zones from Western Europe across to the Far East. Control measures focus on personal protection against tick bites, vaccination in endemic areas, and monitoring of tick and wildlife infection rates to assess risk.