How does infection from an encephalitic tick occur? - briefly
When an infected tick attaches and feeds, virus particles in its saliva are injected into the host’s skin and bloodstream, initiating infection. Transmission usually requires the tick to remain attached for several hours to deliver an infectious dose.
How does infection from an encephalitic tick occur? - in detail
Tick‑borne encephalitis viruses circulate among small mammals, primarily rodents, which serve as natural reservoirs. When a larval or nymphal tick attaches to an infected animal, it ingests blood containing viral particles. The virus penetrates the tick’s midgut epithelium, replicates locally, and subsequently migrates to the salivary glands during the molt to the next developmental stage.
During a later blood meal on a human or another vertebrate host, the tick injects saliva that contains high concentrations of the virus. Salivary secretions facilitate viral entry by suppressing local immune responses and providing a direct pathway into the skin. The virus initially infects dermal dendritic cells and macrophages, then spreads through the lymphatic system to regional lymph nodes. Viremia develops as the virus replicates in peripheral tissues, and neuroinvasion occurs when viral particles cross the blood‑brain barrier, leading to encephalitic disease.
Key variables influencing transmission efficiency include:
- Minimum attachment time of approximately 24 hours; shorter feeding periods markedly reduce viral delivery.
- Tick species and developmental stage; Ixodes ricinus and Ixodes persulcatus are the most competent vectors for European and Asian strains.
- Viral load in the tick’s salivary glands; higher titers correlate with increased infection risk.
- Host factors such as age, immune status, and prior vaccination; immunocompromised individuals experience more severe outcomes.
Preventive strategies focus on reducing tick exposure and interrupting the transmission cycle. Effective measures comprise: