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.