How does encephalitis get into a tick? - briefly
Encephalitis‑causing viruses enter ticks when the arthropods feed on infected vertebrate hosts, ingesting viral particles present in the blood. The virus then replicates within the tick’s salivary glands, enabling transmission during subsequent bites.
How does encephalitis get into a tick? - in detail
Ticks become carriers of encephalitic viruses primarily through blood meals taken from vertebrate hosts that are actively viremic. When a tick attaches to an infected animal, virus particles present in the host’s bloodstream are drawn into the tick’s gut lumen. The viral particles cross the midgut epithelium, entering hemocoelic space where they encounter hemocytes and other immune cells. Successful replication in the midgut leads to dissemination throughout the tick’s internal organs.
Key processes that facilitate this infection cycle include:
- Acquisition during feeding – ingestion of virus‑laden blood while the tick is engorged.
- Midgut invasion – passage of virions across the gut barrier via receptor‑mediated endocytosis or disruption of tight junctions.
- Systemic spread – replication in hemolymph, followed by migration to salivary glands, ovaries, and other tissues.
- Transstadial persistence – maintenance of infection as the tick molts from larva to nymph to adult, allowing the pathogen to survive across developmental stages.
- Co‑feeding transmission – simultaneous feeding of multiple ticks on the same host enables virus transfer without systemic host infection, as virus released from the mouthparts of an infected tick can be taken up by a neighboring uninfected tick.
- Vertical transmission – infected females can pass the virus to offspring through the oocytes, ensuring the next generation starts already infected.
Once the virus reaches the salivary glands, it is secreted with saliva during subsequent blood meals, delivering infectious particles to new hosts. The combination of oral uptake, barrier crossing, replication, and tissue tropism constitutes the complete pathway by which encephalitic agents colonize a tick.