The Role of Ranged Horses in Eco-Epidemiology of Rickettsia raoultii Infection in China

Rickettsia raoultii is a tick-borne pathogen that infects humans; however, the vertebrate hosts of this pathogen have not been clearly defined. Our molecular examination of Rickettsia spp. infecting mammals and ticks in China, identified the gltA, ompA, and 17KD gene sequences of R. raoultii in horses and their ticks. This indicates a role of horses in R. raoultii epidemiology.

A tick bite patient with fever and meningitis co-infected with Rickettsia raoultii and Tacheng tick virus 1: a case report

Background Increasing numbers of tick-borne pathogens are being discovered, including those that infect humans. However, reports on co-infections caused by two or more tick-borne pathogens are scarce. Case presentation A 38-year-old male farmer was bitten by a hard tick, presented with fever (37.7 °C), severe headache and ejection vomiting. Lumbar puncture was performed in the lateral decubitus. The cerebrospinal fluid (CSF) was clear, and analysis showed severe increased pressure (320 mm H2O), mild leukocytosis (126.0 × 106/L, mononuclear cells accounting for 73%) and elevated total protein concentration (0.92 g/L). Bacterial cultures of CSF and blood were negative. The diagnosis of Rickettsia raoultii and Tacheng tick virus 1 (TcTV-1) co-infection was confirmed by amplifying four rickettsial genetic markers and the partial small (S) RNA segment of TcTV-1 from the patient’s blood. The patient gradually recovered after treatment with levofloxacin and ribavirin. Conclusions This is the first reported co-infection case with fever and meningitis caused by R. raoultii and TcTV-1. It is vital to screen for multiple pathogens in tick-bitten patients, especially in those with severe complex symptoms.

Identification and Genetic Diversity Analysis of Rickettsia in Dermacentor Nuttalli Within Inner Mongolia, China

Background The pathogen genus Rickettsia contains the linages spotted fever group, typhus group, transitional group, and the ancestral group, of which the spotted fever group Rickettsia (SFGR) is transmitted by ticks. Dermacentor nuttalli is considered the main vector carrying SFGR. Studying the genetic diversity and population structure of Rickettsia is essential for developing effective control strategies and predicting evolutionary trends of the pathogens. Methods We collected 408 Dermacentor nuttalli in the Inner Mongolia Autonomous region in 2019, detected Rickettsia infection, and characterized the haplotypes. The extracted Rickettsia DNA of the gltA and ompA genes were amplified and sequenced. Result In this study, 10 haplotypes of the gltA gene and 22 haplotypes of the ompA gene were obtained. In the two resulting phylogenetic trees, the haplotypes G1-G7 and G9 of the gltA gene clustered with Rickettsia raoultii, while G8 and G10 clustered with Rickettsia sibirica. Haplotypes O1-O15, O18 and O20-O22 of the ompA gene clustered with Rickettsia raoultii, while O16 and O19 clustered with Rickettsia sibirica. The average haplotype diversity was 0.3 for gltA and 0.7 for ompA, while the average nucleotide diversity was greater than 0.05. Neutrality tests were insignificant for Tajima’s D results and Fu’s Fs results. The fixation index values (FST) showed that the degree of genetic differentiation between most sampled populations was small (FST<0.05), while others were medium (FST>0.05) and large (FST>0.15). Analysis of molecular variance (AMOVA) revealed that the variation within populations was greater than that between populations. The mismatch analysis of Rickettsia showed double peaks. Conclusion We found two genotypes of Rickettsia: Rickettsia raoultii and Rickettsia sibirica. The high genetic diversity of Rickettsia allows for easy adaption to different environments; furthermore, genetic differentiation between populations is small and Rickettsia populations do not show a pedigree geographical structure. The high rates of retention and infestation of Rickettsia in Dermacentor nuttalli together with the animal husbandry exchange in China gradually lead to the genetic characteristics of Rickettsia harmonizing across various regions. Overall, the significant genetic diversity and geographic structure of Rickettsia in Dermacentor nuttalli are critical for SFGR control.

Detection of Rickettsia raoultii in Dermacentor reticulatus and Haemaphysalis inermis ticks in Slovakia

Ticks are vector arthropods responsible for the transmission of several pathogenic agents that affect both human and animal health worldwide. In this study our objective was to analyse, using molecular tools, the bacterial community of Dermacentor reticulatus and Haemaphysalis inermis ticks collected in south-eastern Slovakia. Using real-time PCR, we identified the presence of Rickettsia spp. DNA at levels of 14/59 (23.72 %) and 29/173 (16.76 %) in D. reticulatus and H. inermis, respectively. In addition, using standard PCR and sequencing, we identified the presence of Rickettsia raoultii DNA in 13 ticks belonging to the two investigated species. Rickettsia raoultii blast results revealed an average identification percentage of 99.62 %. Following the results of this molecular study there is a possibility that D. reticulatus and H. inermis play a potential role in the transmission of R. raoultii. To prove the possibility of validity of this hypothesis, we suggest performing experimental models in future studies. Our results can serve as preliminary data for future transmission models.

Replication Kinetics of Rickettsia raoultii in Tick Cell Lines

Rickettsia raoultii is one of the causative agents of tick-borne lymphadenopathy in humans. This bacterium was previously isolated and propagated in tick cell lines; however, the growth characteristics have not been investigated. Here, we present the replication kinetics of R. raoultii in cell lines derived from different tick genera (BME/CTVM23, RSE/PILS35, and IDE8). Tick cell cultures were infected in duplicate with cryopreserved R. raoultii prepared from homologous cell lines. By 12–14 days post infection, 100% of the cells were infected, as visualized in Giemsa-stained cytocentrifuge smears. R. raoultii growth curves, determined by rickettsiae-specific gltA qPCR, exhibited lag, exponential, stationary and death phases. Exponential phases of 4–12 days and generation times of 0.9–2.6 days were observed. R. raoultii in BME/CTVM23 and RSE/PILS35 cultures showed, respectively, 39.5- and 37.1-fold increases compared to the inoculum. In contrast, multiplication of R. raoultii in the IDE8 cultures was 110.1-fold greater than the inoculum with a 7-day stationary phase. These findings suggest variation in the growth kinetics of R. raoultii in the different tick cell lines tested, amongst which IDE8 cells could tolerate the highest levels of R. raoultii replication. Further studies of R. raoultii are needed for a better understanding of its persistence within tick populations.

First report of the molecular detection of human pathogen Rickettsia raoultii in ticks from the Republic of Korea

Background Rickettsial diseases associated with the spotted fever group constitute a growing number of newly identified Rickettsia pathogens and their tick vectors in various parts of the world. At least 15 distinct tick species belonging to six genera have shown the presence of Rickettsia raoultii. Herein, we report the detection of R. raoultii in ticks from the Republic of Korea (ROK). Methods Thirty-five ticks were collected from 29 patients with tick bites in Gwangju Metropolitan City, Jeollanam Province, ROK. The ticks were identified using molecular, morphological, and taxonomic characteristics. All samples were screened for presence of Rickettsia species using nested polymerase chain reactions of their outer membrane protein (ompA) and citrate synthase (gltA) genes. The amplified products were sequenced for subsequent phylogenetic analyses. Results Sequencing data showed the DNA sequences of R. raoultii in three Haemaphysalis longicornis ticks. All three tick samples were 99.4–100% similar to previously reported partial sequences of ompA of R. raoultii strains CP019435 and MF002523, which formed a single clade with the reference strains. Conclusions We provide the first description and molecular identification of R. raoultii detected in H. longicornis ticks in the ROK. This observation extends the geographical distribution of R. raoultii. Screening of human samples for this pathogen will provide information about the prevalence of rickettsial infections in this region.

Molecular detection and genetic diversity of Rickettsia spp. in pet dogs and their infesting ticks in Harbin, northeastern China

Background Pet dogs are important companion animals that share the environment within households, and play an important role in local community life. In addition, pet dogs also are reservoirs of zoonotic agents, including Rickettsia spp., thus increasing the risk of rickettsial infections in humans. It’s meaningful to investigate the epidemiology of rickettsial agents in pet dogs, and make contribute to the surveillance of rickettsioses in human in China. Results In this study, a total of 496 pet dogs’ blood samples and 343 ticks infested in pet dogs were collected, and the presence and prevalence of Rickettsia were determined by amplifying the partial gltA and 17-kDa genes, with an overall positive rate of 8.1 % in blood samples and 14.0 % in tick samples. In addition, the rrs, gltA, groEL, and ompA genes of rickettsial were also recovered to determine the species of Rickettsia detected furtherly. Sequencing blast and phylogenetic analyses revealed the presence of three human pathogenic Rickettsia species (Rickettsia raoultii, Candidatus Rickettsia tarasevichiae and Rickettsia felis) in samples associated with pet dogs. Moreover, all the sequences of Rickettsia that we obtained presented close relationship with others available in GenBank, and Rickettsia raoultii was the most predominant Rickettsia species infected in pet dogs’ blood samples or in tick samples. Conclusions This study provides the molecular epidemiology data about the Rickettsia spp. infection associated with pet dogs in urban areas of Harbin city. Three rickettisae species pathogenic to humans were identified from pet dogs’ blood and the infested ticks in urban areas of Harbin city. Considering the intimate relationship between human and pets, these results indicate the potential transmission risk of human rickettisal infections from pet dogs through ectoparasites, and also highlighting that more attention should be paid to rickettsial infection in pet dogs and the infested ticks from the “One health” perspective.

First Molecular Detection of Human Pathogen Rickettsia Raoultii in Ticks from Republic of Korea

Background: Rickettsial diseases, associated with the spotted fever group (SFG), constitute a growing number of newly identified rickettsia pathogens and their tick vectors, in various parts of the world. At least 15 distinct tick species owing to six genera have shown the presence of Rickettsia raoultii. Here, we report the detection of R. raoultii in ticks from the Republic of Korea (ROK).Methods: A total of 35 ticks, collected from patients of tick bites in Gwangju Metropolitan City, Jeollanam Province, ROK. The ticks were were identified through their molecular, morphological, and taxonomic characteristics. All samples were screened by nested polymerase chain reactions of their outer membrane protein (ompA) and citrate synthase (gltA) genes. The amplified products were sequenced and their phylogenetic analyses were carried out.Results: Sequencing data showed that the DNA sequences of R. raoultii found in the three H. longicornis ticks. All 3 tick samples were 99.4-100% analogous to the previously reported partial sequences of ompA of R. raoultii strains CP019435 and MF002523, forming a single clade with the reference strains.Conclusions: Present study provides the first description and molecular identification of R. raoultii detected in H. longicornis ticks in ROK. This observation extends the geographical distribution of R. raoultii. Screening of human samples for this pathogen will provide information about the prevalence of rickettsial infection in this region.