Abstract
BackgroundRecently, a new rickettsia named ‘Candidatus Rickettsia vini’ belonging to the spotted fever group has been molecularly detected in Ixodes arboricola ticks in Spain, the Czech Republic, Slovakia and Turkey, with prevalence reaching up to 100 %. The aim of this study was to isolate this rickettsia in pure culture, and to describe it as a new Rickettsia species.MethodsA total of 148 ornitophilic nidicolous ticks Ixodes arboricola were collected in a forest near Breclav (Czech Republic) and examined for rickettsiae. Shell vial technique was applied to isolate rickettsiae in Vero cells. Rickettsial isolation was confirmed by optical microscopy and sequencing of partial sequences of the rickettsial genes gltA, ompA, ompB, and htrA. Laboratory guinea pigs and chickens were used for experimental infestations and infections. Animal blood sera were tested by immunofluorescence assay employing crude antigens of various rickettsiae.ResultsRickettsia vini n. sp. was successfully isolated from three males of I. arboricola. Phylogenetic analysis of fragments of 1092, 590, 800, and 497 nucleotides of the gltA, ompA, ompB, and htrA genes, respectively, showed closest proximity of R. vini n. sp. to Rickettsia japonica and Rickettsia heilongjiangensis belonging to the spotted fever group. Experimental infection of guinea pigs and chickens with R. vini led to various levels of cross-reactions of R. vini-homologous antibodies with Rickettsia rickettsii, Rickettsia parkeri, ‘Candidatus Rickettsia amblyommii’, Rickettsia rhipicephali, Rickettsia bellii, and Rickettsia felis. Laboratory infestations by R. vini-infected I. arboricola larvae on chickens led to no seroconversion to R. vini n. sp., nor cross-reactions with R. rickettsii, R. parkeri, ‘Ca. R. amblyommii’, R. rhipicephali, R. bellii or R. felis.ConclusionsOur results suggest that R. vini n. sp. is possibly a tick endosymbiont, not pathogenic for guinea pigs and chickens. Regarding specific phenotypic characters and significant differences of DNA sequences in comparison to the most closely related species (R. japonica and R. heilongjiangensis), we propose to classify the isolate as a new species, Rickettsia vini.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1742-8) contains supplementary material, which is available to authorized users.
Highlights
A new rickettsia named ‘Candidatus Rickettsia vini’ belonging to the spotted fever group has been molecularly detected in Ixodes arboricola ticks in Spain, the Czech Republic, Slovakia and Turkey, with prevalence reaching up to 100 %
This study described and characterized a new species of Rickettsia, R. vini n. sp., isolated from I. arboricola ticks collected in nest-boxes in the Czech Republic
This bacterium was first detected by polymerase chain reaction (PCR) in I. arboricola and I. ricinus immature ticks collected from birds in La Rioja, a vineyard region in Spain [9] and named ‘Ca. R. vini’ [14]
Summary
A new rickettsia named ‘Candidatus Rickettsia vini’ belonging to the spotted fever group has been molecularly detected in Ixodes arboricola ticks in Spain, the Czech Republic, Slovakia and Turkey, with prevalence reaching up to 100 %. Rickettsia spp. have small genomes (1.1–2.1 Mb) resulted from reductive evolution caused by their obligate endosymbiotic relationship to eukaryotic cells [1]. All valid species are associated with arthropods, novel genotypes have been identified in annelids, amoebae and plants [2, 3]. A number of Rickettsia species can propagate in vertebrates, some of them cause diseases in humans and animals, to which they are transmitted by arthropod vectors such as fleas, lice, mites or ticks. Some species are considered non-pathogenic, and novel Rickettsia species reveal to be nearly cosmopolitan [4]
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