Which factors contribute to the spread of Dermacentor reticulatus ticks in the Netherlands

Dermacentor reticulatus plays an important role in the transmission of a range of different tick-borne pathogens. Multiple D. reticulatus populations are present in the Netherlands since 2004 and locations that are considered as founding places for D. reticulatus are therefore continuously surveyed. Moreover, new locations have been identified and checked for ticks in the vegetation. A total of 436 adult D. reticulatus ticks were collected from the vegetation in 9 different locations. In 7 of those 9 locations potential host animals were present (horses, Highlandcows and sheep). 245 ticks will be screened using polymerase chain reaction(PCR) and reverse line blot (RLB) to demonstrate the possible presence of the tick borne pathogens. D. reticulatus was found in a larger variety of vegetation than described in the literature. Locations with a high density of ticks comply with the picture that is reported in the literature which is an open type habitat with a high degree of humidity. However, the habitat in De Panne and Egmond aan Zee, where D. reticulatus has also been found, is much different. This is a sandy and dry habitat in the dunes with some dune grasses and blackberry bushes. How D. reticulatus ticks are spreading in The Netherlands is not entirely clear. It seems, however, that the presence of animals host, mainly livestock, play an important role in the success of D. reticulatus populations in an area. Spreading is most likely caused by relocating livestock to new grazing fields or by dogs that visit endemic areas.