Isolated populations of Ixodes lividus ticks in the Czech Republic and Belgium host genetically homogeneous Rickettsia vini
Abstract
In the last two decades, the advent of molecular methods has revealed a remarkable diversity of rickettsiae (Rickettsiales: Rickettsiaceae) in invertebrates. Several species of these obligate intracellular bacteria are known to cause human infections, hence more attention has been directed towards human-biting ectoparasites.
A spotted fever group Rickettsia sp. was previously detected in Ixodes lividus ticks (Ixodidae) associated with sand martins (Hirundinidae: Riparia riparia). In order to identify whether this rickettsia varies among isolated tick populations, a total of 1758 I. lividus ticks and five Ixodes ricinus ticks (Ixodidae) were collected in the Czech Republic and 148 I. lividus ticks were collected in Belgium, from nests of sand martins, European bee-eaters (Meropidae: Merops apiaster), Eurasian tree sparrows (Passeridae: Passer montanus), and from captured sand martins.
We screened 165 and 78 I. lividus ticks (from the Czech Republic and Belgium, respectively) and all five I. ricinus ticks for the presence of rickettsial DNA. Only I. lividus samples were positive for Rickettsia vini, a spotted fever group rickettsia that commonly infects the tree-hole tick Ixodes arboricola (Ixodidae).
Maximum likelihood analysis of the rickettsial sequences showed that the most closely related organism to R. vini corresponds to an uncharacterized rickettsia detected in Argas lagenoplastis (Argasidae), a nidicolous soft tick of the fairy martin (Hirundinidae: Petrochelidon ariel) in Australia. The observed variability of R. vini sequences from isolated tick populations was low; all 85 sequenced samples were identical to each other in five out of six partial rickettsial genes, except for the sca4 sequence (99.9% identity, 808/809 nt) that differed in I. lividus ticks from two sampling sites in the Czech Republic.