Comparative analysis of microbial communities in different growth stages of Dermacentor nuttalli

Molecular and next-generation sequencing analysis of tick-borne pathogens of Rhipicephalus ticks (Acari: Ixodidae) in cattle and dogs

Ticks are small and adaptable arachnid ectoparasites and global carriers of various pathogens that threaten both human and animal health. They are present in many parts of China. A total of 858 ticks were collected from various regions and hosts, then subjected to species identification based on morphological and molecular characteristics, as described in the authors' previous study. Eighty-three individual tick samples were selected for screening pathogens based on metagenomic next-generation sequencing (mNGS) and polymerase chain reaction (PCR) assays. The genomic DNA of tick species was extracted, and amplification of the bacterial 16S rRNA gene was carried out from DNA of individual ticks using V3-V4 hypervariable regions, before subjecting to metagenomic analysis. Each tick underwent specific PCR tests for identifying the bacterial species present, including Anaplasma, Ehrlichia, Coxiella, and Rickettsia, and also protozoans such as Babesia, Theileria, and Hepatozoon. Illumina NovaSeq sequencing results revealed that the dominant phylum and family in Rhipicephalus spp. were Bacteroidota and Muribaculaceae, respectively. Alpha diversity patterns varied depending on tick sex (R. linnaei only), species and location, but not on host. Furthermore, bacterial pathogens, including A. marginale (58 %, 29/50), A. platys (6 %, 3/50), E. minasensis (2 %, 1/50), Ehrlichia sp. (10 %, 5/50), T. sinensis (24 %, 12/50), T. orientalis (54 %, 27/50) and Coxiella-like bacteria (CLB) (80 %, 40/50) were detected in R. microplus, while E. canis (33.33 %, 10/30), H. canis (20 %, 6/30) and CLB (100 %, 30/30) were detected in R. linnaei. Also, Anaplasma sp. (33.33 %, 1/3), A. marginale (33.33 %, 1/3), R. felis (33.33 %, 1/3) and CLB (100 %, 3/3) were detected in R. haemaphysaloides. Dual and triple co-infections involving pathogens or CLB were detected in 84.00 % of R. microplus, 66.66 % of R. haemaphysaloides, and 33.00 % of R. linnaei. The report on microbial communities and pathogens, which found from Rhipicephalus spp. in Hainan Island, is an important step towards a better understanding of tick-borne disease transmission. This is the first report in the area on the presence of Anaplasma sp., A. marginale, R. felis and Coxiella, in R. haemaphysaloides.

First detection of Candidatus Rickettsia tarasevichiae in Hyalomma marginatum ticks

Ticks are important vectors of zoonotic diseases and play a major role in the circulation and transmission of many rickettsial species. The aim of this study was to investigate the carriage of Candidatus Rickettsia tarasevichiae (CRT) in a total of 1168 ticks collected in Inner Mongolia to elucidate the potential public health risk of this pathogen, provide a basis for infectious disease prevention, control and prediction and contribute diagnostic ideas for clinical diseases that present with fever in populations exposed to ticks. A total of four tick species, Haemaphysalis concinna (n = 21), Dermacentor nuttalli (n = 122), Hyalomma marginatum (n = 148), and Ixodes persulcatus (n = 877), were collected at nine sampling sites in Inner Mongolia, China, and identified by morphological and molecular biological methods. Reverse transcription PCR targeting the 16S ribosomal RNA (rrs), gltA, groEL, ompB and Sca4 genes was used to detect CRT DNA. Sequencing was used for pathogen species confirmation. The molecular epidemiological analysis showed that three species of ticks were infected with CRT, and the overall positive rate was as high as 42%. The positive rate of I. persulcatus collected in Hinggan League city was up to 96%, and that of I. persulcatus collected in Hulun Buir city was 50%. The pool positive rates of D. nuttalli and H. marginatum collected in Bayan Nur city and H. concinna collected in Hulun Buir city were 0%, 28% and 40%, respectively. This study revealed the high prevalence of CRT infection in ticks from Inner Mongolia and the first confirmation of CRT detected in H. marginatum in China. The wide host range and high infection rate in Inner Mongolia may dramatically increase the exposure of CRT to humans and other vertebrates. The role of H. marginatum in the transmission of rickettsiosis and its potential risk to public health should be further considered.