How is encephalitis transmitted from a tick? - briefly
Encephalitis is transmitted when a feeding tick injects virus‑laden saliva into the host’s bloodstream, allowing the pathogen to spread to the central nervous system. The process occurs during the tick’s bite, typically within hours to days after attachment.
How is encephalitis transmitted from a tick? - in detail
Tick‑borne encephalitis results from the transfer of tick‑borne encephalitis virus (TBEV) during a blood meal. Adult female ticks of the genera Ixodes and Dermacentor acquire the virus while feeding on infected small mammals, such as rodents, that serve as natural reservoirs. The virus enters the tick’s midgut, replicates, and migrates to the salivary glands. When the infected tick attaches to a new host and begins to ingest blood, virus‑laden saliva is injected into the bite site, providing direct exposure to the host’s bloodstream.
Key steps in the transmission cycle:
- Acquisition – Larval or nymphal ticks feed on viremic rodents; TBEV is ingested with the blood meal.
- Replication – The virus replicates within the tick’s epithelial cells, amplifying the viral load.
- Dissemination – After replication, the virus spreads to the salivary glands through hemolymph circulation.
- Transmission – During the subsequent feeding stage (often as a nymph or adult), the tick injects saliva containing infectious virions into the host’s skin.
- Co‑feeding – In some cases, non‑infected ticks acquire the virus by feeding adjacent to infected ticks on the same host, without a systemic infection in the host.
The virus remains viable within the tick for months to years, allowing the vector to transmit infection across multiple feeding cycles. Human exposure typically occurs in endemic regions of Central and Eastern Europe and parts of Asia where the tick species thrive in forested or grassland habitats. The incubation period after a bite ranges from 4 to 28 days, after which neurological symptoms may develop.
Preventive measures focus on avoiding tick bites: wearing protective clothing, applying repellents containing DEET or picaridin, performing thorough skin checks after outdoor activities, and promptly removing attached ticks with fine‑tipped forceps. Early removal reduces the likelihood of virus transmission, as the pathogen is usually delivered after the tick has been attached for at least 24 hours.