How long does an encephalitis‑carrying tick survive without food? - briefly
Adult ticks that transmit encephalitis can remain alive for up to a year or longer when unfed, often surviving 12‑18 months in a dormant state. Nymphal stages typically endure several months without a blood meal.
How long does an encephalitis‑carrying tick survive without food? - in detail
Ticks that harbor the tick‑borne encephalitis (TBE) virus can persist for extended periods without a blood meal, but survival varies with species, developmental stage, temperature, and relative humidity.
Adult Ixodes ricinus and I. persulcatus, the primary vectors in Europe and Asia, remain viable for several months when ambient humidity exceeds 80 %. Laboratory trials at 10‑15 °C report adult longevity of 6‑9 months without feeding. At 20‑25 °C and high humidity, the same stage survives 2‑4 months; lower humidity (≤70 %) reduces survival to 1‑2 months due to desiccation.
Nymphs exhibit shorter fasting endurance. Under optimal humidity (≥80 %) and cool temperatures (10‑12 °C), nymphs endure 3‑5 months. Warmer conditions (20 °C) shorten this window to 1‑2 months, and desiccating environments (<70 % RH) further limit survival to less than one month.
Larvae, which rarely carry TBE virus, survive up to 2 months in cool, moist settings; high temperature and low humidity decrease this to a few weeks.
Key factors influencing unfed survival:
- Temperature: Lower temperatures slow metabolic rate, extending fasting periods; higher temperatures accelerate energy depletion.
- Relative humidity: Moisture prevents cuticular water loss; humidity below 70 % markedly shortens lifespan.
- Stage of development: Adults possess larger energy reserves than nymphs and larvae, thus outlasting younger stages.
- Host‑seeking behavior: Questing activity increases exposure to desiccation, reducing survival compared with sheltered conditions.
Field observations corroborate laboratory data: adult ticks collected in autumn can overwinter and re‑quest in spring, indicating a fasting duration of 5‑7 months in temperate climates. Nymphs emerging in late summer may survive through winter only under favorable microclimates, typically 3‑4 months.
In summary, a TBE‑infected tick may remain alive without a blood meal for up to half a year in optimal cool‑humid environments, while adverse conditions compress this period to several weeks.