Microsatellite-based genetic diversity of Dermacentor reticulatus in Europe.

Dermacentor reticulatus, also known as ornate dog tick, is an important vector of the causative agents of various tick-borne diseases in humans, livestock and wild animals. The geographical range of D. reticulatus in Europe is fragmented and divided into two main zones: The Western European and the Eastern European zone. To investigate D. reticulatus population structure through its distribution range we used microsatellite markers and compared the genetic diversity of D. reticulatus in 26 selected sites in the western and eastern European distribution areas. A total of 254 unfed adult D. reticulatus ticks were collected from vegetation and genotyped at 5 microsatellite loci, and altogether 26 alleles were detected. The overall FST value of pairwise comparisons among 26 sampling sites was 0.128 and revealed a moderate genetic differentiation. Bayesian-clustering analysis showed that D. reticulatus forms two genetically distinct groups across Europe. Division of D. reticulatus distribution range into Eastern European and Western European populations with a possible recent overlap in Poland has been supported by molecular data obtained in this study.

New localities of Dermacentor reticulatus ticks in the Baltic countries.

According to previous observations in three Baltic States, Dermacentor reticulatus was found only in Lithuania where it occurred mainly in the central and western parts of the country. During the past decade, evidence about a changing distribution of D. reticulatus in the Baltic countries was provided by the occurrence of canine babesiosis in the new locations in Lithuania and Latvia. In the present study the current distribution of D. reticulatus in Lithuania and Latvia was investigated. Ticks were collected in different habitats in 2013-2014. A total of 3693 questing ticks belonging to D. reticulatus (n = 2789), Ixodes ricinus (n = 896) and I. persulcatus (n=8) were collected in Lithuania and Latvia. Questing D. reticulatus ticks were found in 73.4% (58/79) and in 44.4% (12/28) of the sampling localities in Lithuania and Latvia, respectively. Relative abundances of the ticks in different habitats were compared. All sites with high abundance of D. reticulatus ticks were localized in open areas close to a water basin and mixed forest. The present study demonstrates that during the past two decades D. reticulatus has expanded its range in the Baltic countries. D. reticulatus has been detected in 38 new localities in which this species had not been previously reported. The northern border of D. reticulatus in central Europe moved further to the north. New localities (n = 12) with D. reticulatus occurrence have been found in southern Latvia.