The distribution and spreading pattern of Dermacentor reticulatus over its threshold area in the Czech Republic--how much is range of this vector expanding?

Abstract

Host-seeking Dermacentor reticulatus ticks were detected by flagging method at 46 localities at south-east part of the Czech Republic, in the basins of rivers Morava and Dyje. Exact north-west distribution limits of D. reticulatus were defined in this area for the first time. Detailed prediction map of probabilities of D. reticulatus occurrence was obtained using GIS analysis. Spatial model delimited a south-north gradient in probability across the studied area, with highest probabilities above 0.8 in its southernmost part. Abundance of D. reticulatus varied markedly between localities in interval 0.33-222 of ticks per flag per hour. The highest abundances were in flooded areas at lower streams, towards upper streams abundance and density of these ticks decreased. Females prevailed in samples with population sex ratio of 0.413, significantly deviating from parity. Larvae and nymphs of this species were not detected by flagging. Although D. reticulatus range expansion probably did not reach such a degree as reported in other countries, these ticks became very abundant in some parts of studied area. Since spreading of vector-borne diseases became a problem in Europe, the knowledge of their exact recent geographic ranges is important for future modelling of their shift predictability.