Analysis of Microorganism Diversity in Haemaphysalis longicornis From Shaanxi, China, Based on Metagenomic Sequencing

Evaluation of fipronil efficacy and first molecular report of gamma-aminobutyric acid (GABA) gated chloride channel gene of Rhipicephalus microplus ticks in China and Pakistan

Southern cattle tick, Rhipicephalus (R) microplus, is a major challenge in transmitting Babesia spp., Theileria spp., and Anaplasma spp., worldwide. Mitigation of this tick and associated pathogens is crucial for animal and human-health. In present study, laboratory-based larval packet tests (LPTs) were performed to assess fipronil efficacy against R. microplus ticks collected from four Chinese localities, Nanning, Guangshui, Macheng, and Tengchong. Additionally, we reported first molecular characterization of the full-length gamma-aminobutyric acid (GABA)-gated chloride channel gene of R. microplus ticks from China and Pakistan (Khyber Pakhtunkhwa and Punjab). For LPTs bioassay, fipronil's concentrations (5-ppm, 25-ppm, 50-ppm, 75-ppm, 100-ppm) in acetone and DNase-free water were prepared. The highest average mortality rate of larvae was observed in Nanning (4.34-98.13 %) while lowest in Tengchong (5.70-82.29 %) via triplicate LPTs. The recorded LC50 values were 33.2 ppm, 35.7 ppm, 49.7 ppm, and 55.4 ppm, respectively, for the four localities (Guangshui, Macheng, Nanning, and Tengchong) while the LC99 values were 722 ppm, 827 ppm, 949 ppm, and 1342.3 ppm, respectively. The resistance factors (RR50) were 13.83, 14.88, 20.71, and 23.08, indicating the development of level-II resistance in the tick populations from these regions respectively. Molecularly, consensus sequences of R. microplus GABA-gene from China and Pakistan resulted 99.24-99.52 % and 99.10-99.39 % identities with dieldrin-susceptible NRFS (GQ398111.1) and dieldrin-resistant (GQ398112.1) R. microplus ticks, respectively. Findings revealed 21 single nucleotide polymorphisms (SNPs) [8-non-synonymous (NS) and 13-synonymous (S)], including specifically 10-SNPs from Nanning, 9-SNPs from Macheng, 7-SNPs from Guangshui, 10-SNPs from Tengchong, and 9-SNPs from Pakistani R. microplus full-length GABA gene. Explicitly, we obtained one NS-SNP in TM3 (T-871-G; F-291-V) and two NS-SNPs in TM4 (A-1438-G; N-480-D and A-1439-G; N-480-G) regions of Chinese and Pakistani, while one NS-SNP in TM2 (A-763-G; T-255-A) region of Pakistani R. microplus ticks was documented. Coexistence among SNPs in TM3 (T-871-G; F-291-V), TM4 (A-1439-G; N-480-G) and one linker SNP (A-1378-G; S-460-G) were also recorded. Presence of SNPs and their coexistence suggest the possible tri-dimensional structural modification in GABA-Cl channels that might interfere with binding of fipronil, resulting in development of resistance. This comprehensive research will provide a basis for governmental and pharmaceutical industries for development of effective tick control-strategies as well as to manage the effectiveness and functionality of the available acaricides.

Metagenome reveals the midgut microbial community of Haemaphysalis qinghaiensis ticks collected from yaks and Tibetan sheep

BACKGROUND

Haemaphysalis qinghaiensis is a tick species distributed only in China. Due to its ability to transmit a variety of pathogens, including species of the genera Anaplasma, Rickettsia, Babesia, and Theileria, it seriously endangers livestock husbandry. However, the microbial community of the midgut of H. qinghaiensis females collected from yaks and Tibetan sheep has not yet been characterized using metagenomic sequencing technology.

METHODS

Haemaphysalis qinghaiensis were collected from the skins of yaks and Tibetan sheep in Gansu Province, China. Genomic DNA was extracted from the midguts and midgut contents of fully engorged H. qinghaiensis females collected from the two hosts. Metagenomic sequencing technology was used to analyze the microbial community of the two groups.

RESULTS

Fifty-seven phyla, 483 genera, and 755 species were identified in the two groups of samples. The ticks from the two hosts harbored common and unique microorganisms. At the phylum level, the dominant common phyla were Proteobacteria, Firmicutes, and Mucoromycota. At the genus level, the dominant common genera were Anaplasma, Ehrlichia, and Pseudomonas. At the species level, bacteria including Anaplasma phagocytophilum, Ehrlichia minasensis, and Pseudomonas aeruginosa along with eukaryotes such as Synchytrium endobioticum and Rhizophagus irregularis, and viruses such as the orf virus, Alphadintovirus mayetiola, and Parasteatoda house spider adintovirus were detected in both groups. In addition, the midgut of H. qinghaiensis collected from yaks had unique microbial taxa including two phyla, eight genera, and 23 species. Unique microorganisms in the midgut of H. qinghaiensis collected from Tibetan sheep included two phyla, 14 genera, and 32 species. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that the functional genes of the microbiome of H. qinghaiensis were annotated to six pathways, and the metabolic pathways included 11 metabolic processes, in which the genes involved in carbohydrate metabolism were the most abundant, followed by the genes involved in lipid metabolism.

CONCLUSIONS

These findings indicate that most of the microbial species in the collected H. qinghaiensis ticks were the same in both hosts, but there were also slight differences. The analytical data from this study have enhanced our understanding of the midgut microbial composition of H. qinghaiensis collected from different hosts. The database of H. qinghaiensis microbe constructed from this study will lay the foundation for predicting tick-borne diseases. Furthermore, a comprehensive understanding of tick microbiomes will be useful for understanding vector competency and interactions with ticks and midgut microorganisms.

16S rRNA metabarcoding for the identification of tick-borne bacteria in ticks in the Republic of Korea

Ticks are blood-sucking ectoparasites that act as vectors for transmission of various pathogens. The purpose of this study was to assess tick-borne bacteria, whether pathogenic or not, in ticks distributed in Korea using 16S rRNA metabarcoding and to confirm the results by PCR. Questing ticks were collected from four provinces in Korea in 2021 using the flagging method. After pooling the DNAs from the 61 tick pools (including 372 ticks), the bacterial 16S rRNA V3-V4 hypervariable region was amplified and sequenced using the MiSeq platform. Rickettsia, Ehrlichia, and the endosymbiont Wolbachia were confirmed by conventional PCR and molecular analysis. In total, 6907 ticks (534 pools) were collected and identified as belonging to five species (Haemaphysalis spp., H. longicornis, H. flava, I. nipponensis, and A. testudinarium). Through 16S rRNA metabarcoding, 240 amplicon sequence variants were identified. The dominant taxa were Rickettsiella and Coxiella. Additionally, pathogenic bacteria such as Rickettsia and Ehrlichia, endosymbiotic bacteria such as Wolbachia and Spiroplasma were identified. Polymerase chain reaction (PCR) was performed to confirm the presence of Rickettsia, Ehrlichia, Bartonella, and Wolbachia in individual ticks. Overall, 352 (65.92%) of 534 pools tested positive for at least one of the screened tick-borne bacteria. Rickettsia was the most prevalent (61.42%), followed by Wolbachia (5.05%). Ehrlichia was detected in 4.86% of tested samples, whereas Bartonella was not detected. In this study, 16S rRNA metabarcoding revealed the presence of Rickettsia, Wolbachia, and Ehrlichia, in that order of abundance, while showing absence of Bartonella. These results were confirmed to exhibit the same trend as that of the conventional PCR. Therefore, large-scale screening studies based on pooling, as applied in this study, will be useful for examining novel or rare pathogens present in various hosts and vectors.

Aedes Mosquito Virome in Southwestern Cameroon: Lack of Core Virome, But a Very Rich and Diverse Virome in Ae. africanus Compared to Other Aedes Species

In Cameroon, Aedes mosquitoes transmit various arboviruses, posing significant health risks. We aimed to characterize the Aedes virome in southwestern Cameroon and identify potential core viruses which might be associated with vector competence. A total of 398 Aedes mosquitoes were collected from four locations (Bafoussam, Buea, Edea, and Yaounde). Aedes albopictus dominated all sites except for Bafoussam, where Aedes africanus prevailed. Metagenomic analyses of the mosquitoes grouped per species into 54 pools revealed notable differences in the eukaryotic viromes between Ae. africanus and Ae. albopictus, with the former exhibiting greater richness and diversity. Thirty-seven eukaryotic virus species from 16 families were identified, including six novel viruses with near complete genome sequences. Seven viruses were further quantified in individual mosquitoes via qRT-PCR. Although none of them could be identified as core viruses, Guangzhou sobemo-like virus and Bafoussam mosquito solemovirus, were highly prevalent regionally in Ae. albopictus and Ae. africanus, respectively. This study highlights the diverse eukaryotic virome of Aedes species in southwestern Cameroon. Despite their shared genus, Aedes species exhibit limited viral sharing, with varying viral abundance and prevalence across locations. Ae. africanus, an understudied vector, harbors a rich and diverse virome, suggesting potential implications for arbovirus vector competence.

Surveillance of tick-borne bacteria infection in ticks and forestry populations in Inner Mongolia, China

Ticks are one of the most important vectors that can transmit pathogens to animals and human beings. This study investigated the dominant tick-borne bacteria carried by ticks and tick-borne infections in forestry populations in Arxan, Inner Mongolia, China. Ticks were collected by flagging from May 2020 to May 2021, and blood samples were collected from individuals at high risk of acquiring tick-borne diseases from March 2022 to August 2023. The pooled DNA samples of ticks were analyzed to reveal the presence of tick-borne bacteria using high-throughput sequencing of the 16S rDNA V3-V4 region, and species-specific polymerase chain reaction (PCR) related to sequencing was performed to confirm the presence of pathogenic bacteria in individual ticks and human blood samples. All sera samples were examined for anti-SFGR using ELISA and anti-B. burgdorferi using IFA and WB. A total of 295 ticks (282 Ixodes persulcatus and 13 Dermacentor silvarum) and 245 human blood samples were collected. Rickettsia, Anaplasma, Borrelia miyamotoi, and Coxiella endosymbiont were identified in I. persulcatus by high-throughput sequencing, while Candidatus R. tarasevichiae (89.00%, 89/100), B. garinii (17.00%, 17/100), B. afzelii (7.00%, 7/100), and B. miyamotoi (7.00%, 7/100) were detected in I. persulcatus, as well the dual co-infection with Candidatus R. tarasevichiae and B. garinii were detected in 13.00% (13/100) of I. persulcatus. Of the 245 individuals, B. garinii (4.90%, 12/245), R. slovaca (0.82%, 2/245), and C. burnetii (0.41%, 1/245) were detected by PCR, and the sequences of the target genes of B. garinii detected in humans were identical to those detected in I. persulcatus. The seroprevalence of anti-SFGR and anti-B. burgdorferi was 5.71% and 13.47%, respectively. This study demonstrated that Candidatus R. tarasevichiae and B. garinii were the dominant tick-borne bacteria in I. persulcatus from Arxan, and that dual co-infection with Candidatus R. tarasevichiae and B. garinii was frequent. This is the first time that B. miyamotoi has been identified in ticks from Arxan and R. solvaca has been detected in humans from Inner Mongolia. More importantly, this study demonstrated the transmission of B. garinii from ticks to humans in Arxan, suggesting that long-term monitoring of tick-borne pathogens in ticks and humans is important for the prevention and control of tick-borne diseases.