How do ticks become carriers of encephalitis? - briefly
Ticks acquire encephalitis‑causing viruses when they ingest infected blood during a blood meal, after which the pathogen establishes in the salivary glands. The infection persists through molting stages, enabling the tick to transmit the virus to new hosts in later feedings.
How do ticks become carriers of encephalitis? - in detail
Ticks acquire the capacity to transmit encephalitis‑causing viruses through a defined sequence of biological events. The process begins when a larval or nymphal tick feeds on an infected vertebrate host, such as a small mammal or bird that carries the virus in its bloodstream. During blood ingestion, the pathogen enters the tick’s midgut, where it survives the digestive environment.
After ingestion, the virus crosses the midgut epithelium and enters the hemocoel, the body cavity that distributes nutrients. From there, it reaches the salivary glands, the organ responsible for delivering the pathogen to subsequent hosts during feeding. Successful migration requires the virus to evade the tick’s innate immune responses, including antimicrobial peptides and phagocytic hemocytes.
Once established in the salivary glands, the virus can be transmitted to a new host during the next blood meal. This transmission persists across developmental stages—a phenomenon known as transstadial maintenance—allowing the tick to remain infectious as it molts from larva to nymph and from nymph to adult.
Key factors influencing vector competence include:
- Tick species – Ixodes ricinus, Dermacentor variabilis, and Haemaphysalis spp. are recognized as efficient transmitters of tick‑borne encephalitis viruses.
- Viral strain – Certain genotypes replicate more rapidly within tick tissues, enhancing transmission potential.
- Environmental conditions – Temperature and humidity affect tick development rates and viral replication kinetics.
- Host availability – Frequent feeding on competent reservoir hosts sustains the infection cycle.
The combination of pathogen acquisition during a blood meal, migration to the salivary apparatus, and preservation of infectivity through molting establishes the tick as a carrier capable of spreading encephalitis‑inducing viruses to humans and other mammals.