Abstract
BackgroundRickettsia spp. are human pathogens that cause a number of diseases and are transmitted by arthropods, such as ixodid ticks. Estonia is one of few regions where the distribution area of two medically important tick species, Ixodes persulcatus and I. ricinus, overlaps. The nidicolous rodent-associated Ixodestrianguliceps has also recently been shown to be present in Estonia. Although no data are available on human disease(s) caused by tick-borne Rickettsia spp. in Estonia, the presence of three Rickettsia species in non-nidicolous ticks has been previously reported. The aim of this study was to detect, identify and partially characterize Rickettsia species in nidicolous and non-nidicolous ticks attached to rodents in Estonia.ResultsLarvae and nymphs of I.ricinus (n = 1004), I. persulcatus (n = 75) and I.trianguliceps (n = 117), all removed from rodents and shrews caught in different parts of Estonia, were studied for the presence of Rickettsia spp. by nested PCR. Ticks were collected from 314 small animals of five species [Myodes glareolus (bank voles), Apodemus flavicollis (yellow necked mice), A.agrarius (striped field mice), Microtus subterranius (pine voles) and Sorex araneus (common shrews)]. Rickettsial DNA was detected in 8.7% (103/1186) of the studied ticks. In addition to identifying R.helvetica, which had been previously found in questing ticks, we report here the first time that the recently described I.trianguliceps-associated Candidatus Rickettsia uralica has been identified west of the Ural Mountains.Graphical
Highlights
Rickettsia spp. are human pathogens that cause a number of diseases and are transmitted by arthropods, such as ixodid ticks
Rickettsial DNA was detected in 8.7% (103/1186) of the studied ticks, with positivity rates between tick species varying from zero for I. persulcatus to 3.4% (4/117) for I. trianguliceps to 10.0% (99/993) for I. ricinus (Table 2)
As animal samples were not analyzed for the presence of Rickettsia spp., it is unknown whether ticks acquired the pathogen via transstadial or transovarial transmission, co-feeding or blood meal
Summary
Rickettsia spp. are human pathogens that cause a number of diseases and are transmitted by arthropods, such as ixodid ticks. No data are available on human disease(s) caused by tickborne Rickettsia spp. in Estonia, the presence of three Rickettsia species in non-nidicolous ticks has been previously reported. Research on the circulation of Rickettsia spp. is still ongoing, btoh in vectors, which are mainly fleas and ticks, and in the latter’s main hosts (small mammals, wild and domestic animals). This is fairly wide research area, and new species are constantly being discovered, such as I. trianguliceps-associated Ca. R. uralica found in the Ural Mountains in Russia [7]. R. tarasevichiae, that have been found in China and Europe [12,13,14]
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