title: Temporal dynamics of the tick Ixodes ricinus in northern Europe: epidemiological implications.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FI-40014, Jyväskylä, Finland. claire.c.cayol@jyu.fi.
authors.forename: Claire
authors.identifier: http://orcid.org/0000-0001-7744-3510
authors.initials: C
authors.lastname: Cayol
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FI-40014, Jyväskylä, Finland.
authors.forename: Esa
authors.initials: E
authors.lastname: Koskela
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FI-40014, Jyväskylä, Finland.
authors.forename: Tapio
authors.initials: T
authors.lastname: Mappes
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FI-40014, Jyväskylä, Finland.
authors.forename: Anja
authors.initials: A
authors.lastname: Siukkola
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FI-40014, Jyväskylä, Finland.
authors.forename: Eva R
authors.initials: ER
authors.lastname: Kallio
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000469:parasitology; D005260:Female; D018884:Ixodes / Q000502:physiology*; D007814:Larva; D008297:Male; D008954:Models, Biological; D009758:Nymph; D011157:Population Dynamics; D012621:Seasons; D013984:Tick Infestations / Q000469:parasitology / Q000662:veterinary; D013997:Time Factors
keywords: Ixodes ricinus; Population dynamics; Public health; Rodent host; Seasonality