Abstract
BackgroundRickettsia species belonging to the spotted fever group (SFG) cause infections in humans, domestic animals and wildlife. At least ten SFG Rickettsia species are known to occur in China. However, the distribution of rickettsiae in ticks and fleas in the border region of northwestern China have not been systematically studied to date.ResultsA total of 982 ticks (Rhipicephalus turanicus, Dermacentor marginatus, D. nuttalli and Haemaphysalis punctata) and 5052 fleas (18 flea species from 14 species of wild mammals) were collected in ten and five counties, respectively, of Xinjiang Uygur Autonomous Region (northwestern China). Tick and flea species were identified according to morphological and molecular characteristics. Seven sets of primers for amplifying the 17-kDa antigen gene (17-kDa), citrate synthase gene (gltA), 16S rRNA gene (rrs), outer membrane protein A and B genes (ompA, ompB), surface cell antigen 1 gene (sca1) and PS120-protein encoding gene (gene D) were used to identify the species of rickettsiae. Nine Rickettsia species have been detected, seven of them in ticks: R. aeschlimannii, R. conorii, R. raoultii, Rickettsia sibirica, R. slovaca, R. massiliae and “Candidatus R. barbariae”. In addition, R. bellii and two genotypes of a rickettsia endosymbiont (phylogenetically in an ancestral position to R. bellii) have been detected from flea pools.ConclusionsThis study provides molecular evidence for the occurrence of several SFG rickettsiae in Rhipicephalus turanicus, Dermacentor nuttalli and D. marginatus. Furthermore, R. bellii and two ancestral rickettsia endosymbionts are present in fleas infesting wild rodents in the border regions of northwestern China. These data extend our knowledge on the diversity of rickettsiae in Central Asia.
Highlights
Rickettsia species belonging to the spotted fever group (SFG) cause infections in humans, domestic animals and wildlife
R. bellii and two ancestral rickettsia endosymbionts are present in fleas infesting wild rodents in the border regions of northwestern China
Two genotypes of a rickettsia endosymbiont have been identified for the first time in Rhadinopsylla cedestis and Nosopsyllus laeviceps laeviceps fleas. These results indicate that some flea species infesting wild rodents in the border regions might carry different, probably ancient Rickettsia species or genotypes
Summary
Rickettsia species belonging to the spotted fever group (SFG) cause infections in humans, domestic animals and wildlife. The distribution of rickettsiae in ticks and fleas in the border region of northwestern China have not been systematically studied to date. Rickettsiae are obligate intracellular Gram-negative bacteria causing infection in humans, domestic animals and wildlife [1, 2]. Their vectors are typically ticks, fleas or mites, but rickettsiae were shown to be present in several other arthropod groups [3, 4]. Seven species of rickettsiae (including R. aeschlimannii, R. conorii, R. raoultii, Rickettsia sibirica, R. slovaca, R. massiliae and “Candidatus R. barbariae”) were shown to be present in ticks or fleas in Xinjiang Uygur Autonomous Region (XUAR) [7, 8]
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