Vectors of disease at the northern distribution limit of the genus Dermacentor in Eurasia: D.\xa0reticulatus and D.\xa0silvarum

Franz Rubel,Ivan S Kholodilov,Oxana A Belova,Ana L García-Pérez,Katharina Brugger,Olaf Kahl,Yuliya M Didyk,Lina Kurzrock

doi:10.1007/s10493-020-00533-y

Abstract

The two ixodid tick species Dermacentor reticulatus (Fabricius) and Dermacentor silvarum Olenev occur at the northern distribution limit of the genus Dermacentor in Eurasia, within the belt of 34{-}60^circ ~ hbox {N} latitude. Whilst the distribution area of D. reticulatus extends from the Atlantic coast of Portugal to Western Siberia, that of D. silvarum extends from Western Siberia to the Pacific coast. In Western Siberia, the distribution areas of the two Dermacentor species overlap. Although the two tick species are important vectors of disease, detailed information concerning the entire distribution area, climate adaptation, and proven vector competence is still missing. A dataset was compiled, resulting in 2188 georeferenced D. reticulatus and 522 D. silvarum locations. Up-to-date maps depicting the geographical distribution and climate adaptation of the two Dermacentor species are presented. To investigate the climate adaptation of the two tick species, the georeferenced locations were superimposed on a high-resolution map of the Köppen–Geiger climate classification. The frequency distribution of D. reticulatus under different climates shows two major peaks related to the following climates: warm temperate with precipitation all year round (57%) and boreal with precipitation all year round (40%). The frequency distribution of D. silvarum shows also two major peaks related to boreal climates with precipitation all year round (30%) and boreal winter dry climates (60%). Dermacentor silvarum seems to be rather flexible concerning summer temperatures, which can range from cool to hot. In climates with cool summers D. reticulatus does not occur, it prefers warm and to a lesser extent hot summers. Lists are given in this paper for cases of proven vector competence for various agents of both Dermacentor species. For the first time, the entire distribution areas of D. reticulatus and D. silvarum were mapped using georeferenced data. Their climate adaptations were quantified by Köppen profiles.

Highlights

The two ixodid tick species, Dermacentor reticulatus (Fabricius) and Dermacentor silvarum Olenev are endemic at the northern distribution limit of the genus Dermacentor in Eurasia up to approximately 60◦ N
Knowledge on the geographical distribution of D. reticulatus and D. silvarum in Eurasia is based on the existing datasets of Rubel et al (2016) with 1207 D. reticulatus locations, and 181 D. silvarum locations compiled by Zhang et al (2019)
The latitudinal belt, in which D. reticulatus occurs in Eurasia, is 5◦ wider than recently described for only Europe (Rubel et al 2016)

Summary

Introduction

The two ixodid tick species, Dermacentor reticulatus (Fabricius) and Dermacentor silvarum Olenev are endemic at the northern distribution limit of the genus Dermacentor in Eurasia up to approximately 60◦ N.Dermacentor reticulatus (in former Russian literature often called D. pictus) is the second most often reported tick species after Ixodes ricinus in central Europe (Rubel et al 2014). Preferred habitats are alluvial forests where it can survive flooding for certain periods (Nosek 1972). Unfed adults are quite long-lived with a life span of up to 3–4 years (Balashov 1972). They are active from late August/September through April/May, interrupted by low temperatures or snow cover in the winter, and enter a behavioural diapause in summer (Belozerov 1982). Oviposition takes place exclusively in spring and the resultant short-lived larvae and nymphs have their main activity periods in July and August, respectively, irrespective of their geographic origin (Kahl and Dautel 2013). It is known to be infected with bacteria such as Rickettsia raoultii (Barandika et al 2008)

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Conclusion