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. 2018 Dec 4;11(1):620.
doi: 10.1186/s13071-018-3168-y.

"Candidatus Neoehrlichia mikurensis" in Ixodes ricinus ticks collected near the Arctic Circle in Norway

Clarinda Larsson  1 , Dag Hvidsten  2   3 , Snorre Stuen  4 , Anna J Henningsson  5   6 , Peter Wilhelmsson  7   8
Affiliations

"Candidatus Neoehrlichia mikurensis" in Ixodes ricinus ticks collected near the Arctic Circle in Norway

Clarinda Larsson et al. Parasit Vectors. .

Abstract

Background: "Candidatus Neoehrlichia mikurensis" is a gram-negative bacterium belonging to the family Anaplasmataceae that, in Europe, is transmitted by Ixodes ricinus ticks. "Candidatus N. mikurensis" can cause a severe systemic inflammatory syndrome, neoehrlichiosis, mostly in persons with other underlying diseases. To date, "Ca. N. mikurensis" has been found in ticks in different countries in Asia and Europe, but never as far north as at the Arctic Circle.

Methods: A total of 1104 I. ricinus ticks collected from vegetation and from animals in northern Norway (64-68°N) were analysed for the prevalence of "Ca. N. mikurensis". Of them, 495 ticks were collected from vegetation by flagging and 609 ticks were collected from dogs and cats. Total nucleic acid extracted from the ticks were converted to cDNA and analyzed with real-time PCR targeting the 16S rRNA gene of "Ca. N. mikurensis". Positive samples were further analysed by nested PCR and sequencing.

Results: "Candidatus N. mikurensis" was detected in 11.2% of all collected I. ricinus ticks in northern Norway. The prevalence differed between ticks collected from vegetation (18.2%; 90/495) compared to ticks collected from dogs and cats (5.6%; 34/609). The ticks from dogs and cats were collected in Brønnøy area and seven additional districts further north. The prevalence of "Ca. N. mikurensis" in these ticks differed between geographical localities, with the highest prevalence in the Brønnøy area.

Conclusions: The detection of "Ca. N. mikurensis" in I. ricinus ticks from the Arctic Circle in northern Norway indicates potential risk for tick-bitten humans at this latitude to be infected with "Ca. N. mikurensis".

Keywords: Arctic Circle; Ixodes ricinus; Neoehrlichiosis; Norway; Tick-borne pathogen; “Candidatus Neoehrlichia mikurensis”.

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Conflict of interest statement

Ethics approval and consent to participate

Ethical approval has not been relevant for this study, because the analyses have been performed on cDNA from ticks that have either been collected in nature or removed from animals as part of the regular animal welfare.

Consent for publication

Not applicable

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
a The study area covers 8 districts in northern Norway (from 64°56'N–68°48'N) across the Arctic Circle (66°33'N). The Vesterålen and Lofoten archipelago (hatched area, left) and Narvik city (hatched area, right) were not included in the study. b Scatter diagram of the origin of ticks in the study area (red dot = one single tick). In the southernmost district (Brønnøy) 244 ticks were collected, and in the northernmost district (Harstad) 6 ticks. c Sketch map showing the study area in relation to western Europe. Copyright: Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by-nc-nd/4.0/deed.no). Citation: Hvidsten et al. (2014) Ixodes ricinus and Borrelia prevalence at the Arctic Circle in Norway. Ticks Tick Borne Diseases. 2014;5:107–12 [14]
Fig. 2
Fig. 2
a Of 609 samples from I. ricinus ticks collected from dogs and cats in northern Norway, 21.3% were infected with Borrelia and/or “Ca. N. mikurensis”. b Of 495 samples from I. ricinus ticks collected by flagging in northern Norway, 41.4% were infected with Borrelia and/or “Ca. N. mikurensis”
See this image and copyright information in PMC

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