Where do ticks get encephalitis from? - briefly
Ticks acquire encephalitis viruses by feeding on infected vertebrate reservoirs, chiefly rodents and certain bird species. The virus then persists in the tick’s salivary glands and can be transmitted to new hosts during subsequent blood meals.
Where do ticks get encephalitis from? - in detail
Ticks acquire the virus that causes tick‑borne encephalitis (TBE) while feeding on infected vertebrate hosts. The virus circulates in natural foci where specific mammals and birds serve as reservoirs. Small rodents—particularly the bank vole (Myodes glareolus) and the yellow‑necked mouse (Apodemus flavicollis)—maintain high levels of viremia, allowing immature ticks (larvae and nymphs) to become infected during blood meals. Larger mammals such as sheep, goats, and cattle may also harbor the virus, though they usually develop low‑grade infections that do not produce severe disease. Certain bird species, especially ground‑feeding passerines, can transport infected ticks over long distances, facilitating the spread of foci.
The infection cycle proceeds as follows:
- Larval stage: Uninfected larvae hatch from eggs and seek a first blood meal, often from a rodent. If the host is viremic, the larva ingests the virus.
- Molting to nymph: The virus persists through the molt, and the nymph emerges already infected.
- Nymphal feeding: The infected nymph feeds again, typically on another small mammal, amplifying the virus within the local host population.
- Molting to adult: After the nymphal stage, the tick molts into an adult, retaining the virus.
- Adult feeding: Adult ticks may feed on larger mammals or humans, transmitting the virus through saliva during the bite.
Environmental conditions that favor tick activity—humid forests, grasslands, and mountainous regions—correlate with the distribution of TBE foci. Human exposure occurs when people enter these habitats for recreation or work, allowing infected ticks to attach and transmit the virus. Control measures focus on reducing tick populations, vaccinating at‑risk individuals, and limiting contact with known reservoir hosts.