Vectors of disease at the northern distribution limit of the genus Dermacentor in Eurasia: D. reticulatus and D. silvarum

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 • 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.

Atlas of ticks (Acari: Argasidae, Ixodidae) in Germany

“…The northernmost German location of D. reticulatus flagged from vegetation was reported in 2020 by OK at the Baltic Sea coast in the port of Rostock (Rubel et al. 2020 ). An even more northern location (but unconfirmed as yet) on the island of Sylt is also known from a citizen science project (Drehmann et al.…”

“…The global distribution of the ornate dog tick D. reticulatus , also known as the marsh tick in Germany, was recently mapped by Rubel et al. ( 2020 ). Accordingly, its distribution extends from the Atlantic coast of Portugal to Western Siberia, 9° W–88° E, within the latitude range 34–60° N. In Germany, D. reticulatus is particularly widespread and common in the eastern federal states of Brandenburg, Saxonia, Saxonia-Anhalt and Berlin.…”

“…The sources of this data compilation are documented in Rubel et al. ( 2020 ) and have been supplemented by the following number of locations: 199 (Nauke 2007 ), 11 (Silaghi et al. 2020 ) and 10 OK.…”

“…The coordinates are given in decimal degrees with a measure of accuracy divided into high (± 30 m), medium (± 1 km) and low (± 10 km) precision, identical to those previously used by Rubel et al. ( 2014 , 2018 , 2020 ).…”

“…For this purpose, information is incorporated from distribution maps recently published, e.g., for Dermacentor reticulatus (Rubel et al. 2020 ) and Haemaphysalis concinna (Rubel et al. 2018 ).…”