The importance of study duration and spatial scale in pathogen detection—evidence from a tick-infested island

Abstract

Ticks (Acari: Ixodoidea) are among the most common vectors of zoonotic pathogens worldwide. While research on tick-borne pathogens is abundant, few studies have thoroughly investigated small-scale spatial differences in their occurrence. Here, we used long-term cloth-dragging data of Ixodes ricinus and its associated, known and putative pathogens (Borrelia burgdorferi s.l., Borrelia miyamotoi, Anaplasma phagocytophilum, Rickettsia spp., Candidatus Neoehrlichia mikurensis, Bartonella spp., Babesia spp., and tick-borne encephalitis virus, TBEV) from a small, well-studied island in southwestern Finland to analyze potential temporal and spatial differences in pathogen prevalence and diversity between and within different biotopes. We found robust evidence indicating significant dissimilarities in B. burgdorferi s.l., A. phagocytophilum, Rickettsia, and Ca. N. mikurensis prevalence, even between proximal study areas on the island. Moreover, during the 6 years of the ongoing study, we witnessed the possible emergence of TBEV and Ca. N. mikurensis on the island. Finally, the stable occurrence of a protozoan pathogen that has not been previously reported in Finland, Babesia venatorum, was observed on the island. Our study underlines the importance of detailed, long-term tick surveys for public health. We propose that by more precisely identifying different environmental factors associated with the emergence and upkeep of enzootic pathogen populations through rigorous longitudinal surveys, we may be able to create more accurate models for both current and future pathogen distributions.

Acknowledgements

We would like to thank Niko Tanski, Pauliina Pajala, and Päivi Kotitalo for help with field surveys and laboratory work. This study was financially supported by The Jane and Aatos Erkko Foundation, University of Turku Graduate School (Doctoral Programme in Biology, Geography and Geology), Maj and Tor Nessling Foundation, Jenny and Antti Wihuri Foundation, Turku University Foundation, The Varsinais-Suomi Regional Fund of the Finnish Cultural Foundation, and MD-PhD Sakari Alhopuro.

Author contributions

J.J.S. drafted the manuscript, participated in the design of the study and field data collection, carried out molecular lab work and data analysis, and participated in statistical analyses; T.K. participated in the design of the study, helped draft the manuscript, and designed the statistical analyses; S.M. carried out molecular lab work; J.H., I.V., R.P., & I.E.S. conceived the study, participated in the design of the study, coordinated the study, and helped draft the manuscript; E.J.V. designed and carried out molecular lab work, participated in the design of the study, and helped draft the manuscript. All authors gave final approval for publication.

Conflict of interest

The authors declare that they have no conflict of interest.

Electronic supplementary material

Supplementary Information accompanies this paper at (10.1038/s41426-018-0188-9).

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