How does a tick become infected with the encephalitis virus? - briefly
Ticks become carriers of the encephalitis virus when they ingest it from infected vertebrate hosts—typically birds or small mammals—during a blood meal, allowing the virus to replicate in the tick’s midgut and migrate to the salivary glands. Subsequent feedings transmit the virus to new hosts.
How does a tick become infected with the encephalitis virus? - in detail
Ticks acquire encephalitis viruses primarily during blood feeding on infected vertebrate hosts. The virus resides in the host’s bloodstream and enters the tick’s mouthparts as the arthropod pierces the skin. After ingestion, the pathogen passes through the midgut epithelium, replicates in the hemocoel, and disseminates to the salivary glands, where it becomes ready for transmission to the next host.
Key mechanisms of acquisition and maintenance:
- Host‑to‑tick transmission – adult females, nymphs, and larvae feed on rodents, birds, or larger mammals that carry detectable levels of virus in their blood. Even brief feeding periods can deliver sufficient viral particles for infection.
- Transstadial persistence – once the virus infects a tick, it remains viable through molting. A larva that acquires the pathogen can retain it as it develops into a nymph, and subsequently into an adult, preserving the infection cycle.
- Co‑feeding transmission – adjacent ticks feeding simultaneously on the same host can exchange virus without systemic host viremia. Salivary secretions and localized skin inflammation facilitate this direct transfer.
- Vertical transmission (transovarial) – infected females may deposit virus‑laden eggs, producing progeny that hatch already infected. This route sustains the pathogen in tick populations even when vertebrate host availability is low.
Environmental and biological factors influencing infection rates include:
- Seasonal activity peaks that align tick feeding with periods of high host viremia.
- Host species competence: small mammals such as Myodes voles exhibit prolonged viremia, increasing the probability of tick infection.
- Tick species specificity: Ixodes ricinus and Dermacentor reticulatus display differing efficiencies in virus acquisition and replication, affecting regional transmission dynamics.
In summary, a tick becomes a carrier of encephalitis virus by ingesting viral particles from an infected host during blood meal, maintaining the pathogen through developmental stages, and potentially passing it to offspring or neighboring ticks. These processes collectively enable the persistence and spread of the virus within tick populations and to new vertebrate hosts.