BACKGROUND : Autochthonous populations of Dermacentor reticulatus ticks in the Netherlands were discovered after
fatal cases of babesiosis occurred in resident dogs in 2004. The presence of D. reticulatus in the Netherlands has
also linked with the emergence of piroplasmosis in the resident horse population. The aim of this study was to put
together results of continued surveillance of field sites and hosts for this tick in the Netherlands and also in Belgium
and determine their infection status for Babesia and Theileria species.
METHODS : Ticks were collected from the vegetation at 11 locations between 2011 and 2013. D. reticulatus ticks were
also collected from different hosts between 2007 and 2013. Ticks were screened by PCR and reverse line blot (RLB).
RESULTS : A total of 1368 D. reticulatus ticks were collected from 4 previously known field locations and from 5 new
locations in the Netherlands and from 2 sites in Belgium (one old and one new location). A total of 855 ticks collected
from 8 locations in the Netherlands and 2 locations in Belgium were tested. Fourteen ticks (1,64%) collected at 4 field
locations (Dintelse Gorzen, Rozenburg, Slikken van de Heen and St. Philipsland) were positive for Babesia canis, whereas
two ticks were positive for Babesia caballi, one tick in the Dintelse Gorzen in the Netherlands and one tick was found
positive in De Panne in Belgium.
A further 1092 D. reticulatus ticks were collected between 2007 and 2013 from 40 dogs (132 ticks), two ticks from two
humans, 51 ticks from 15 horses, two ticks from two cats, one tick from a roe deer, whereas most ticks (904) were
collected from cattle (n = 25). Ticks were found throughout the year on dogs in nearly all provinces of the Netherlands.
None of the ticks collected from these hosts were infected.
CONCLUSIONS : D. reticulatus is continuing its spread into novel areas. The finding that some autochthonous ticks are
infected with B. canis and B. caballi poses a threat to the resident dog and horse population and justifies year-round tick