Temporal dynamics of the tick Ixodes ricinus in northern Europe : epidemiological implications
Cayol, C., Koskela, E., Mappes, T., Siukkola, A., & Kallio, E. (2017). Temporal dynamics of the tick Ixodes ricinus in northern Europe : epidemiological implications. Parasites and Vectors, 10 (1), 166. doi:10.1186/s13071-017-2112-x
Published in
Parasites and VectorsDate
2017Discipline
Ekologia ja evoluutiobiologiaCopyright
© the Authors, 2017. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License.
Background: Tick-borne pathogens pose an increasing threat to human and veterinary health across the northern
hemisphere. While the seasonal activity of ticks is largely determined by climatic conditions, host-population dynamics are
also likely to affect tick abundance. Consequently, abundance fluctuations of rodents in northern Europe are expected to
be translated into tick dynamics, and can hence potentially affect the circulation of tick-borne pathogens. We quantified
and explained the temporal dynamics of the tick Ixodes ricinus in the northernmost part of its European geographical
range, by estimating (i) abundance in vegetation and (ii) infestation load in the most common rodent species in the
study area, the bank vole Myodes glareolus.
Results: Ixodes ricinus nymphs and adult females, the life stages responsible for the most of tick bites in humans, peaked
in May-June and August-September. Larvae and nymphs were simultaneously active in June and abundance of questing
larvae and nymphs in the vegetation showed a positive association with bank vole abundance. Moreover, infesting larvae
and nymphs were aggregated on bank voles, and the infestation of bank voles with I. ricinus larvae and nymphs was
positively associated with bank vole abundance.
Conclusion: Our results indicate early summer and early autumn as periods of increased risk for humans to encounter
I. ricinus ticks in boreal urban forests and suggest a 2 years life-cycle for I. ricinus with two cohorts of ticks during the same
year. Moreover, we identified a simultaneous activity of larvae and nymphs which allows co-feeding on the rodent host,
which in turn supports the transmission of several important zoonotic tick-borne pathogens. Finally, we showed that a
high density of the rodent host may enhance the risk that ticks and, potentially, tick-borne pathogens pose to
human health.
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