Where does tick‑borne encephalitis come from in ticks? - briefly
The virus is acquired by ticks while feeding on infected small mammals such as rodents, and it persists through transstadial transmission as the tick develops. Adult females can also pass the pathogen to their offspring via transovarial transmission, ensuring its continuity in tick populations.
Where does tick‑borne encephalitis come from in ticks? - in detail
Tick‑borne encephalitis virus (TBEV) persists in the vector through several biological mechanisms. Adult female ticks can transmit the virus to their offspring via transovarial passage; eggs and larvae emerging from infected females already contain viral particles. This vertical route ensures that newly hatched ticks enter the environment already infected.
Horizontal acquisition occurs when unfed ticks feed on vertebrate reservoirs that maintain high viremia. Primary reservoir species include small mammals such as bank voles (Myodes glareolus), wood mice (Apodemus sylvaticus), and certain ground‑feeding birds. During a blood meal, the virus enters the tick’s midgut, crosses the gut barrier, and disseminates to the salivary glands, where it becomes available for transmission to the next host.
Co‑feeding among ticks feeding in close proximity on the same host permits virus exchange without systemic infection of the host. This non‑viremic transmission sustains the virus in tick populations even when reservoir host viremia is low or absent.
Environmental conditions influence the prevalence of infected ticks. Warm, humid climates favor tick development and increase the density of both vectors and reservoir hosts, thereby enhancing the probability of virus circulation. Seasonal activity peaks of nymphs and adults correspond to periods of heightened human exposure.
Key points summarizing the sources of TBEV in ticks:
- Transovarial transmission: infected females → infected larvae.
- Acquisition from reservoirs: feeding on viremic rodents and birds.
- Co‑feeding transmission: virus exchange between adjacent ticks on the same host.
- Ecological factors: climate, habitat suitability, host density.
These processes collectively maintain the viral cycle within tick populations and determine the risk of human infection.