How does a tick transmit encephalitis? - briefly
When a tick attaches and feeds, it deposits saliva that carries the encephalitis virus into the host’s skin. The virus spreads through the bloodstream, reaches the central nervous system, and induces brain inflammation.
How does a tick transmit encephalitis? - in detail
Ticks acquire encephalitis‑causing flaviviruses while feeding on an infected vertebrate. The virus enters the tick’s midgut, where it replicates in epithelial cells and spreads to the hemocoel. From there it reaches the salivary glands, establishing a persistent infection that can endure through molting (trans‑stadial transmission). When the tick attaches to a new host, virus particles are released in the saliva alongside anticoagulant and immunomodulatory compounds that facilitate blood ingestion and suppress local immune responses. The saliva is injected into the host’s dermal tissue, where the virus encounters dendritic cells, macrophages, and keratinocytes, initiating replication and subsequent spread to the central nervous system.
Key biological steps:
- Acquisition: Ingestion of virus‑laden blood during the larval or nymphal stage.
- Midgut replication: Viral replication in gut epithelium, overcoming the peritrophic matrix.
- Systemic dissemination: Movement through hemolymph to secondary tissues, especially salivary glands.
- Salivary gland infection: Establishment of a productive infection that persists across developmental stages.
- Transmission: Release of virions with saliva during subsequent blood meals; co‑feeding can also transfer virus between ticks without systemic host infection.
The virus exploits tick salivary proteins (e.g., anticoagulants, anti‑inflammatory agents) to enhance entry into host cells and evade early immune detection. After entry, the pathogen replicates locally, then spreads via peripheral nerves or bloodstream to the brain, where it induces inflammation and neuronal damage characteristic of encephalitic disease.