Molecular detection and characterization of Rickettsiae in ticks and mites collected from small rodents in Curonian Spit, Lithuania

Abstract

The genus Rickettsia comprises obligate intracellular gram-negative bacteria, of which many cause human infections in all continents inhabited by humans in the world. Rickettsiae are characterized by complex life-cycles and diversity of hosts and transmission strategies. The arthropod vectors are important in the natural maintenance of rickettsial pathogens. Information on the circulation of Rickettsiae and their association with different arthropod vectors in the Baltic countries is scarce. The aim of our study was to investigate the prevalence and diversity of Rickettsia spp. in ticks and mites parasitizing different species of rodents in the Curonian Spit of Lithuania. A total of 238 rodents of six different species were collected. Rodents were found to be infested with Ixodes ricinus ticks (n=596) and 5 species of parasitic mites (n=550) from Laelapidae family (Laelaps agilis, Hyperlaelaps microti, Haemogamassus nidi, Eulaelaps stabularis, Myonyssus gigas). Rickettsia DNA in ectoparasites was detected using a nested PCR that targeted partial gltA gene. Identification of Rickettsia species was based on sequencing and phylogenetic analysis of 17kDa and gltA genes. Infection rates were calculated as the maximum likelihood estimation (MLE). Rickettsia DNA was detected in I. ricinus larvae and nymphs and in for mite species. Rickettsia-positive I. ricinus ticks were found on Apodemus flavicollis, Myodes glareolus, Micromys minutus, Microtus oeconomus and M. arvalis rodents. Infected mites were collected from A. flavicollis and M. minutus. The infection rate was found higher in I. ricinus ticks (MLE = 26.5%) compared with mites (MLE = 9.3%). Mites feeding on rodents harboured R. helvetica, R. felis and unidentified Rickettsia sp. In I. ricinus only R. helvetica was detected. [...]