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First report on the occurrence of Rickettsia slovaca and Rickettsia raoultii in Dermacentor silvarum in China.

ABSTRACT: BACKGROUND: Rickettsioses are among both the longest known and most recently recognized infectious diseases. Although new spotted fever group rickettsiae have been isolated in many parts of the world including China, Little is known about the epidemiology of Rickettsia pathogens in ticks from Xinjiang Autonomous Region of China. METHODS: In an attempt to assess the potential risk of rickettsial infection after exposure to ticks in Xinjiang Uygur Autonomous Region of China, a total of 200 Dermacentor silvarum ticks collected in Xinyuan district were screened by polymerase chain reaction based on the outer membrane protein A gene. RESULTS: 22 of the 200 specimens (11%) were found to be positive by PCR. Phylogenetic analysis of OmpA sequences identified two rickettsial species, Rickettsia raoultii (4.5%) and Rickettsia slovaca (6.5%). CONCLUSIONS: This study has reported the occurrence of Rickettsia raoultii and Rickettsia slovaca in Xinjiang Autonomous Region of China and suggests that Dermacentor silvarum could be involved in the transmission of rickettsial agents in China. Further studies on the characterization and culture of rickettsial species found in Dermacentor silvarum should be performed to further clarify this. Additionally, the screening of human specimens for rickettsial disease in this region will define the incidence of infection.

SUBMITTER: Tian ZC

PROVIDER: S-EPMC3292836 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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First report on the occurrence of Rickettsia slovaca and Rickettsia raoultii in Dermacentor silvarum in China.

Tian Zhan-Cheng ZC Liu Guang-Yuan GY Shen Hui H Xie Jun-Ren JR Luo Jin J Tian Mei-Yuan MY

Parasites & vectors 20120119

<h4>Background</h4>Rickettsioses are among both the longest known and most recently recognized infectious diseases. Although new spotted fever group rickettsiae have been isolated in many parts of the world including China, Little is known about the epidemiology of Rickettsia pathogens in ticks from Xinjiang Autonomous Region of China.<h4>Methods</h4>In an attempt to assess the potential risk of rickettsial infection after exposure to ticks in Xinjiang Uygur Autonomous Region of China, a total o ...[more]

PMID: 22257726

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Project description:BackgroundMelophagus ovinus (Diptera: Hippoboscidae), a hematophagous ectoparasite, is mainly found in Europe, Northwestern Africa, and Asia. This wingless fly infests sheep, rabbits, and red foxes, and causes inflammation, wool loss and skin damage. Furthermore, this parasite has been shown to transmit diseases, and plays a role as a vector. Herein, we investigated the presence of various Rickettsia species in M. ovinus.MethodsIn this study, a total of 95 sheep keds were collected in Kuqa County and Alaer City southern region of Xinjiang Uygur Autonomous Region, northwestern China. First, collected sheep keds were identified on the species level using morphological keys and molecular methods based on a fragment of the 18S ribosomal DNA gene (18S rDNA). Thereafter, to assess the presence of rickettsial DNA in sheep keds, the DNA of individual samples was screened by PCR based on six Rickettsia-specific gene fragments originating from six genes: the 17-kilodalton antigen gene (17-kDa), 16S rRNA gene (rrs), surface cell antigen 4 gene (sca4), citrate synthase gene (gltA), and outer membrane protein A and B genes (ompA and ompB). The amplified products were confirmed by sequencing and BLAST analysis ( https://blast.ncbi.nlm.nih.gov/Blast.cgi?PROGRAM=blastn&PAGE_TYPE=BlastSearch&LINK_LOC=blasthome ).ResultsAccording to its morphology and results of molecular analysis, the species was identified as Melophagus ovinus, with 100% identity to M. ovinus from St. Kilda, Australia (FN666411). DNA of Rickettsia spp. were found in 12 M. ovinus samples (12.63%, 12/95). Rickettsia raoultii and R. slovaca were confirmed based on phylogenetic analysis, although the genetic markers of these two rickettsial agents amplified in this study showed molecular diversity.ConclusionsThis is the first report of R. raoultii and R. slovaca DNA in M. ovinus. Rickettsia slovaca was found for the first time around the Taklimakan Desert located in China. This finding extends the geographical range of spotted fever group rickettsiae.

Project description:BackgroundContinuous culture of tick cell lines has proven a valuable asset in isolating and propagating several different vector-borne pathogens, making it possible to study these microorganisms under laboratory conditions and develop serological tests to benefit public health. We describe a method for effective, cost- and labor-efficient isolation and propagation of Rickettsia raoultii using generally available laboratory equipment and Rhipicephalus microplus cells, further demonstrating the usefulness of continuous tick cell lines. R. raoultii is one of the causative agents of tick-borne lymphadenopathy (TIBOLA) and is, together with its vector Dermacentor reticulatus, emerging in novel regions of Europe, giving rise to an increased threat to general public health.MethodsDermacentor reticulatus ticks were collected in the Donau-Auen (Lobau) national park in Vienna, Austria. The hemolymph of ten collected ticks was screened by PCR-reverse line blot for the presence of rickettsial DNA. A single tick tested positive for R. raoultii DNA and was used to infect Rhipicephalus microplus BME/CTVM2 cells.ResultsSixty-five days after infection of the tick-cell line with an extract from a R. raoultii-infected tick, we observed intracellular bacteria in the cultured cells. On the basis of microscopy we suspected that the intracellular bacteria were a species of Rickettsia; this was confirmed by several PCRs targeting different genes. Subsequent sequencing showed 99-100 % identity with R. raoultii. Cryopreservation and resuscitation of R. raoultii was successful. After 28 days identical intracellular bacteria were microscopically observed.ConclusionsR. raoultii was successfully isolated and propagated from D. reticulatus ticks using R. microplus BME/CTVM2 cells. The isolated strain shows significant molecular variation compared to currently known sequences. Furthermore we show for the first time the successful cryopreservation and resuscitation of R. raoultii.

Project description:Ticks of the genus Dermacentor Koch, 1844 (Acari: Ixodidae) are poorly known systematically due to their habitation in harsh topographic environments and high mountains. Dermacentor ticks are diversely distributed in the Palearctic, Nearctic, and Oriental regions. There is no available information on the occurrence of Dermacentor marginatus in Pakistan; thus, the current investigation aimed the first morphological and molecular confirmation of this species and associated Anaplasma marginale and Rickettsia raoultii. Ticks were collected from goats (Capra hircus) and morphologically identified. Genomic DNA was extracted from 18/26 (69.23%) tick specimens, including 11 males and 7 females (1 unfed and 6 fed females). Extracted DNA was subjected to PCR for the amplification of genetic markers like 16S rDNA and cox1 for ticks, 16S rDNA for Anaplasma spp., and gltA and ompB for Rickettsia spp. A total of 26 D. marginatus ticks composed of 19 males (73.07%) and 7 females (26.9%) [1 (3.84%) unfed and 6 (23.07%) fed females] were collected from goats. According to amplicons via BLAST analysis, the 16S rDNA sequence showed 97.28-98.85% identity and the cox1 sequence showed 95.82-98.03% identity with D. marginatus. Additionally, the 16S rDNA sequence for Anaplasma sp. was detected in D. marginatus that showed 100% identity with Anaplasma marginale. Rickettsial gltA and ompB sequences for Rickettsia sp. showed 100% identity with Rickettsia raoultii. In phylogenetic analysis, ticks' 16S rDNA and cox1 sequences clustered with the same species. In phylogenetic analysis, A. marginale based on 16 rDNA clustered with A. marginale, while gltA and ompB sequences clustered with R. raoultii. This is the first study on the genetic characterization of D. marginatus and associated A. marginale and R. raoultii in Pakistan. The northern areas of Pakistan, which need to be explored in terms of ticks and associated pathogens due to their zoonotic threats, have been neglected due to the inaccessible climatic conditions.

Project description:Tick cell lines play an important role in research on ticks and tick-borne pathogenic and symbiotic microorganisms. In an attempt to derive continuous Dermacentor reticulatus cell lines, embryo-derived primary cell cultures were set up from eggs laid by field ticks originally collected as unfed adults in The Netherlands and maintained for up to 16 months. After several months, it became evident that cells in the primary cultures were infected with a Rickettsia-like intracellular organism. Supernatant medium containing some D. reticulatus cells was inoculated into cultures of 2 Rhipicephalus (Boophilus) microplus cell lines, BME/CTVM2 and BME/CTVM23, where abundant growth of the bacteria occurred intracellularly on transfer to both cell lines. Bacterial growth was monitored by light (live, inverted microscope, Giemsa-stained cytocentrifuge smears) and transmission electron microscopy revealing heavy infection with typical intracytoplasmic Rickettsia-like bacteria, not present in uninfected cultures. DNA was extracted from bacteria-infected and uninfected control cultures, and primers specific for Rickettsia 16S rRNA, ompB, and sca4 genes were used to generate PCR products that were subsequently sequenced. D. reticulatus primary cultures and both infected tick cell lines were positive for all 3 Rickettsia genes. Sequencing of PCR products revealed 99-100% identity with published Rickettsia raoultii sequences. The R. raoultii also grew abundantly in the D. nitens cell line ANE58, poorly in the D. albipictus cell line DALBE3, and not at all in the D. andersoni cell line DAE15. In conclusion, primary tick cell cultures and cell lines are useful systems for isolation and propagation of fastidious tick-borne microorganisms. In vitro isolation of R. raoultii from Dutch D. reticulatus confirms previous PCR-based detection in field ticks, and presence of the bacteria in the tick eggs used to initiate the primary cultures confirms that transovarial transmission of this Rickettsia occurs.

Dataset Information

First report on the occurrence of Rickettsia slovaca and Rickettsia raoultii in Dermacentor silvarum in China.

Publications

First report on the occurrence of Rickettsia slovaca and Rickettsia raoultii in Dermacentor silvarum in China.

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