University of Oulu

Jani J. Sormunen, Veli-Matti Pakanen, Riikka Elo, Satu Mäkelä, Jukka Hytönen, Absence of Francisella tularensis in Finnish Ixodes ricinus and Ixodes persulcatus ticks, Ticks and Tick-borne Diseases, Volume 12, Issue 6, 2021, 101809, ISSN 1877-959X,

Absence of Francisella tularensis in Finnish Ixodes ricinus and Ixodes persulcatus ticks

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Author: Sormunen, Jani J.1; Pakanen, Veli-Matti2,3; Elo, Riikka1,4;
Organizations: 1Biodiversity Unit, University of Turku, Turku, Finland
2Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
3Ecology and Genetics Research Unit, University of Oulu, Oulu, Finland
4Tampere Museum of Natural History, Museum center Vapriikki, Tampere, Finland
5Department of Biology, University of Turku, Turku, Finland
6Institute of Biomedicine, University of Turku, Turku, Finland
7Laboratory Division, Clinical Microbiology, Turku University Hospital, Turku, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.9 MB)
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Language: English
Published: Elsevier, 2021
Publish Date: 2021-11-08


Francisella tularensis subsp. holarctica is the causative agent of tularaemia in Europe. Finland is a high-incidence region for tularaemia, with mosquito bites as the most common sources of infection. However, in Central and Western Europe, ticks (Acari: Ixodidae) have been suggested as the main vectors. Indeed, several studies have reported the pathogen from the locally most common human-biting tick species, Ixodes ricinus. In Finland, the occurrence of the pathogen in ticks has started receiving attention only recently. Here, we collate previous tick screening data from Finland regarding F. tularensis as well as present the results from a novel screening of roughly 15 000 I. ricinus and I. persulcatus collected from across the country.

In total, 14 878 ticks collected between 2015 and 2020 were screened for F. tularensis using a TaqMan-based qPCR assay targeting the 23 KDa gene. The combined screening efforts of the current and previous studies, encompassing roughly 20 000 ticks, did not find any positive ticks. Given the negative results despite the considerable sample size, it appears that the pathogen is not circulating in local tick populations in Finland. We discuss some possible reasons for the lack of the bacterium in ticks in this high-incidence region of tularaemia.

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Series: Ticks and tick-borne diseases
ISSN: 1877-959X
ISSN-E: 1877-9603
ISSN-L: 1877-959X
Volume: 12
Issue: 6
Article number: 101809
DOI: 10.1016/j.ttbdis.2021.101809
Type of Publication: A1 Journal article – refereed
Field of Science: 1181 Ecology, evolutionary biology
Funding: We would like to thank Jane and Aatos Erkko Foundation, Maj and Tor Nessling Foundation and Sakari Alhopuro Foundation for financial support of the study.
Copyright information: © 2021 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY license (