University of Oulu

Pakanen, V., Sormunen, J.J., Sippola, E. et al. Questing abundance of adult taiga ticks Ixodes persulcatus and their Borrelia prevalence at the north-western part of their distribution. Parasites Vectors 13, 384 (2020).

Questing abundance of adult taiga ticks Ixodes persulcatus and their Borrelia prevalence at the north-western part of their distribution

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Author: Pakanen, Veli-Matti1,2; Sormunen, Jani J.3; Sippola, Ella4;
Organizations: 1Department of Biological and Environmental Sciences, University of Gothenburg, P.O. Box 463, Gothenburg, 40530, Sweden
2Ecology and Genetics Research Unit, University of Oulu, P.O. Box 3000, 90014, Oulu, Finland
3Biodiversity Unit, University of Turku, 20014, Turku, Finland
4Department of Biology, University of Turku, 20014, Turku, Finland
5Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40041, Jyväskylä, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.5 MB)
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Language: English
Published: Springer Nature, 2020
Publish Date: 2020-08-19


Background: Because ixodid ticks are vectors of zoonotic pathogens, including Borrelia, information of their abundance, seasonal variation in questing behaviour and pathogen prevalence is important for human health. As ticks are invading new areas northwards, information from these new areas are needed. Taiga tick (Ixodes persulcatus) populations have been recently found at Bothnian Bay, Finland. We assessed seasonal variation in questing abundance of ticks and their pathogen prevalence in coastal deciduous forests near the city of Oulu (latitudes 64–65°) in 2019.

Methods: We sampled ticks from May until September by cloth dragging 100 meters once a month at eight study sites. We calculated a density index (individuals/100 m²) to assess seasonal variation. Samples were screened for Borrelia burgdorferi (sensu lato) (including B. afzelii, B. garinii, B. burgdorferi (sensu stricto) and B. valaisana), Borrelia miyamotoi, Anaplasma phagocytophilum, Rickettsia spp., Neoehrlichia mikurensis, Francisella tularensis and Bartonella spp., Babesia spp. and for the tick-borne encephalitis virus.

Results: All except one nymph were identified as I. persulcatus. The number of questing adults showed a strong peak in May (median: 6.5 adults/100 m²), which is among the highest values reported in northern Europe, and potentially indicates a large population size. After May, the number of questing adults declined steadily with few adults still sampled in August. Nymphs were present from May until September. We found a striking prevalence of Borrelia spp. in adults (62%) and nymphs (40%), with B. garinii (51%) and B. afzelii (63%) being the most common species. In addition, we found that 26% of infected adults were coinfected with at least two Borrelia genospecies, mainly B. garinii and B. afzelii, which are associated with different host species.

Conclusions: The coastal forest environments at Bothnian Bay seem to provide favourable environments for I. persulcatus and the spread of Borrelia. High tick abundance, a low diversity of the host community and similar host use among larvae and nymphs likely explain the high Borrelia prevalence and coinfection rate. Research on the infestation of the hosts that quantifies the temporal dynamics of immature life stages would reveal important aspects of pathogen circulation in these tick populations.

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Series: Parasites & vectors
ISSN: 1756-3305
ISSN-E: 1756-3305
ISSN-L: 1756-3305
Volume: 13
Article number: 384
DOI: 10.1186/s13071-020-04259-z
Type of Publication: A1 Journal article – refereed
Field of Science: 1181 Ecology, evolutionary biology
Funding: JS received funding from the Jane and Aatos Erkko Foundation and the Maj and Tor Nessling Foundation. DB received funding from Stiftelsen Olle Enqvist Byggmästare and ERK from the Academy of Finland (329332 and 329308).
Academy of Finland Grant Number: 329332
Detailed Information: 329332 (Academy of Finland Funding decision)
329308 (Academy of Finland Funding decision)
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