Tick-borne pathogens and the vector potential of ticks in China

Molecular detection of novel Jingmen tick virus in hard ticks from diverse hosts in Guangxi, southwestern China

BACKGROUND

Ticks are the second most important vectors of arboviruses after mosquitoes, and they also serve as reservoir hosts for some zoonotic diseases. It is essential to understand the prevalence of tick-borne viruses in ticks from different sampling sites and vectors, as this information can facilitate the surveillance and prevention of arboviral infectious diseases.

METHODS

We systematically collected ticks from a variety of animals, including wildlife and domestic livestock, across 18 distinct regions in Guangxi Zhuang Autonomous Region(Guangxi). We then identified the ticks using traditional morphological classification and molecular biology methods to investigate the diversity of ticks in the regionWe also systematically examined the diversity of viruses carried by ticks using comprehensive virological methods based on viral metagenomics. We performed phylogenetic and recombination analyses for the assembled viral sequences.

RESULTS

We collected 1286 Ixodidae from 18 sampling sites in 17 districts of Guangxi. We identified 4 genera and 6 species of Ixodidae. We annotated 2 unclassified viruses and 13 known viral families. We assembled 208 nucleotide sequences and obtained six near full-length sequences of Jingmen tick virus (JMTV). Among these sequences, GXTV-PC4.2 and GXTV-43 were new mutant strains of JMTV. We detected genetic recombination of JMTV in segments 2, 3, and 4 of JMTV.

CONCLUSIONS

Our study uncovers a diverse tick fauna in Guangxi, including 4 genera and 6 species, and a broad virome with 13 viral families and 2 novel viruses. The JMTV, in particular, shows significant genetic diversity and potential for cross-species transmission, marked by new strains and recombination events. These findings underscore the need for vigilant tick-borne disease surveillance in Guangxi.

The genome-wide characterisation of cold shock proteins and prominent roles involved in cold response by configuring metabolic pathways in Haemaphysalis longicornis

Cold shock proteins are relatively conserved in evolution and are involved in regulating various life activities, including cell proliferation, nutritional stress and cold adaptation. However, information about the function and regulation of cold shock proteins in ticks during cold response remains meagre. In the present study, six cold shock protein genes were identified from the important vector tick Haemaphysalis longicornis, which were named as HlY-box1, HlY-box2, HlY-box3, HlY-box4, HlY-box5 and HlY-box6. Spatiotemporal expression dynamics revealed dynamic expressions varied significantly after low-temperature treatment, with different expression patterns observed over prolonged exposure periods. Then the function and regulation of cold shock protein genes during the cold response of H. longicornis were explored. RNA interference (RNAi) efficiently knocked down these genes, significantly increasing tick mortality under cold stress. Transcriptomic analysis following HlY-box4 knockdown identified 336 differentially expressed genes (DEGs), which were mainly annotated in the MAPK signalling pathway and metabolism pathway. Proteomic analysis identified 632 differentially expressed proteins associated with ATP-dependent chromatin remodelling, metabolic pathway, spliceosome, ribosome and nucleoplasmic transport pathways. The results highlight the critical roles of cold shock proteins (CSPs) in tick cold responses, primarily through regulating metabolic pathways, and provide a foundation for further exploration of their molecular mechanisms.

Distribution and Prevalence of Ticks and Tick-Borne Pathogens at the Wildlife-Livestock Interface in Africa: A Systematic Review

Ticks and tick-borne diseases (TBDs) significantly impact African animal health and agricultural productivity, especially at the wildlife-livestock interface. This systematic review analyzed 20 eligible studies from East, Southern, and limited parts of Central Africa to determine the distribution and prevalence of key tick species and associated pathogens. Rhipicephalus appendiculatus and Amblyomma variegatum were the most commonly reported tick species, with R. appendiculatus exhibiting up to 50.5% prevalence in cattle and buffalo in Uganda. The most frequently detected pathogens included Theileria parva, Anaplasma marginale, and Coxiella burnetii, with T. parva showing high prevalence in cattle populations coexisting with wildlife. Notably, geographic disparities were observed, with Central and West Africa being underrepresented. Most pathogen detections occurred in Kenya, Uganda, Tanzania, Botswana, and South Africa, indicating regional hotspots for tick-borne disease transmission. This review highlights the urgent need for enhanced surveillance, region-specific vector control programs, and integrated One Health approaches to address the ecological, agricultural, and zoonotic challenges of tick-borne pathogens across Africa.

Molecular Detection of Tick-Borne Bacterial Pathogens in Ticks and Rodents from the China-Vietnam Border

Ticks and tick-borne diseases constitute a crucial focus for the health of both humans and animals worldwide. Although numerous studies on tick-borne diseases have been conducted in China, reports on tick-borne pathogens in ticks and rodents from the China-Vietnam border are scarce. In this study, we investigated tick-borne bacterial pathogens, including Rickettsia, Anaplasmataceae, and Borrelia, in nine rodents (Rattus norvegicus) and 88 ticks collected from cattle and rodents in Jingxi, a city at the China-Vietnam border. Through molecular detection and sequence analysis, four known tick-borne pathogens were identified. Specifically, Rickettsia japonica was detected in 46.3% (37/80) of Haemaphysalis cornigera; Anaplasma phagocytophilum and Candidatus Neoehrlichia mikurensis were identified in one Ixodes granulatus and one rodent, respectively; and Borrelia valaisiana was detected in two I. granulatus. Additionally, a potentially novel species of Rickettsia, provisionally named Rickettsia sp. JX, was detected in 41.3% (33/80) of Ha. cornigera, one Rhipicephalus microplus, three I. granulatus, and nine rodents, whereas a potentially novel species of Borrelia, tentatively named Borrelia sp. JX, was detected in one I. granulatus. To the best of our knowledge, this is the first report on tick-borne bacterial pathogens in ticks and rodents from the China-Vietnam border. These results expand the knowledge of the geographical distribution and vector diversity of tick-borne bacterial pathogens in China and are conducive to the evaluation of thee potential public health risk.

Inter-species dynamics of non-coding RNAs: Impact on host immunomodulation and pathogen survival

Non-coding RNAs (ncRNAs) are composed of nucleotides that do not encode proteins but instead serve as guides. It interacts with amino acids at precise genomic sites, influencing chromatin structure and gene expression. These ncRNAs contribute to numerous inter-species dynamics, including those within the vector-host-pathogen triad. Vector-associated ncRNAs are released into hosts to combat the host immune system and sustain arthropod viability. Conversely, hosts may utilize specific ncRNAs as part of their defences to counteract pathogen-carrying vectors. Moreover, pathogens transmitted through vectors' saliva into hosts carry ncRNAs that enhances their virulence. While recent investigations have primarily focused on vector-associated ncRNAs in animal hosts, only a few have explored the functions of pathogen-associated ncRNAs and their role in initiating infections. Our review delves into the historical prospects of ncRNAs, mechanisms by which pathogen-derived ncRNAs influence host-pathogen interactions, regulate gene expression, and evade host defences. Ultimately, it underscores the importance ncRNAs mediated regulatory network in vector-host-pathogen dynamics, offering new strategies to combat vector-borne diseases and enhance public health outcomes.

Aquaporins modulate the cold response of Haemaphysalis longicornis via changes in gene and protein expression of fatty acids

BACKGROUND

As ectotherms that spend most of their life in the environment (off-host), ticks face challenges in maintaining water balance, and some species must cope with severe low winter temperatures. Aquaporins (AQPs) are essential membrane proteins that enhance cold tolerance in many animals by regulating homeostatic processes. However, the dynamic expressions and involvement of aquaporins in the cold stress of ticks remain unclear.

METHODS

In the present study, three AQP genes, HlAQP2, HlAQP3, and HlAQP5, belonging to the major intrinsic protein (MIP) superfamily, were characterized from the important vector tick Haemaphysalis longicornis. Then, multiple bioinformatics analyses were performed. Quantitative real-time PCR (qPCR) was used to detect different expressions of H. longicornis genes under different cold treatment conditions. RNA interference was used to explore the relationship between AQP and the cold response of H. longicornis. Additionally, proteomic and transcriptomic analyses were used to investigate the mechanisms underlying the effects of AQPs on cold response in ticks.

RESULTS

The amino acid sequence of AQPs shows high homology in Ixodida, with HlAQP2 and HlAQP5 proteins comprising two asparagine-proline-alanine (NPA) motifs, whereas HlAQP3 protein was featured by glycerol facilitator GlpF channel. The spatiotemporal expression of AQPs in H. longicornis varied significantly after low temperature treatment, and different expression patterns were observed over prolonged exposure periods. RNAi knockdown of AQPs significantly increased tick mortality after treatment at a sublethal temperature of - 14 °C for 2 h. Proteomic and transcriptomic analysis revealed that the differentially expressed genes and proteins caused by the knockdown of AQPs are mainly enriched in the fatty acid metabolism pathway.

CONCLUSIONS

The above results indicated that AQPs could regulate tick cold response by modulating water balance and fatty acid metabolism.

The Prevalence of Tick-Borne Encephalitis Virus in the Ticks and Humans of China from 2000 to 2023: A Systematic Review and Meta-Analysis

This study presents a systematic review and meta-analysis of studies on tick-borne encephalitis virus (TBEV) prevalence in ticks and human hosts in China, published between 2000 and 2023. Extensive searches were conducted on four databases-PubMed, CNKI, VIP, and Wan Fang. The findings indicated overall pooled prevalence estimates of TBEV infection in ticks and humans of 5.8% and 9.0%, respectively. The prevalence of TBEV in ticks was 4.8% (95%CI, 4.5-7.1%) during 2000-2010 and increased to 6.3% (95%CI, 4.7-7.8%) during 2011-2023, and was mainly distributed in Jilin (13.4%; 95%CI, 8.3-18.4%) and Inner Mongolia (4.5%; 95%CI, 1.8-7.1%). The prevalence of TBEV was higher in Dermacentor silvarum than in other tick species (8.1%; 95%CI, 3.2-12.9%). The seroprevalence of TBEV in humans increased from 4.7% (95%CI, 2.9-6.4%) during 2000-2010 to 17.6% (95%CI, 11.3-23.8%) during 2011-2023. Simultaneously, the analysis results of the population characteristics showed that females, forestry workers, military personnel, and farmers were found to be susceptible, and the highest seroprevalence was noted among homemakers and unemployed individuals. There were certain differences in the seroprevalence among populations in different provinces, especially in Xinjiang and Heilongjiang. This study can provide a reference for a more comprehensive and in-depth investigation of ticks and humans infected with TBEV in China.

Tick Control Strategies: Critical Insights into Chemical, Biological, Physical, and Integrated Approaches for Effective Hard Tick Management

Ticks and tick-borne diseases significantly impact animal health, public health, and economic productivity globally, particularly in areas where the wildlife-livestock interface complicates management. This review critically examines the current control strategies, focusing on chemical, biological, physical, and integrated pest management (IPM) approaches. Chemical acaricides, while effective, are increasingly challenged by resistance development and environmental concerns. Biological approaches, including natural predators and entomopathogenic fungi, and physical interventions, such as habitat modification, provide sustainable alternatives but require further optimization. IPM stands out as the most promising long-term solution, integrating multiple approaches to enhance efficacy while reducing environmental risks. Emerging innovations, such as nanotechnology-enhanced acaricides and next-generation vaccines, offer promising avenues for improved tick control. Addressing the complex challenges of tick management requires tailored strategies, interdisciplinary collaboration, and sustained research investment in both veterinary and public health contexts.

The first direct detection of spotted fever group Rickettsia spp. diversity in ticks from Ningxia, northwestern China

BACKGROUND

Tick-borne infectious diseases caused by the spotted fever group Rickettsia (SFGR) have continuously emerging, with many previously unidentified SFGR species reported. The prevalence of SFGRs in northwestern China remains unclear. This study aimed to examine the prevalence of SFGRs and Anaplasma species by analyzing tick samples collected from the Ningxia region.

METHODS

During 2022-2023, ticks were collected from Ningxia, northwestern China, and screened using PCR to amplify target genes (16S rRNA, gltA, ompA and groEL). The amplicons were confirmed by Sanger sequencing. Single-gene sequences and concatenated sequences were used to infer phylogenetic relationships for identifying Rickettsia species.

RESULTS

Out of the 425 DNA samples, a total of 210 samples tested positive for SFGRs in ticks from Ningxia, China, with a relatively high positive rate of 49.4% (210/425). Eight spotted fever group rickettsiae and one Anaplasma species were identified and characterized, including Rickettsia raoultii (102, 24.0%), R. aeschlimannii (65, 15.3%), R. sibirica (12, 2.8%), R. slovaca (4, 0.9%), R. heilongjiangensis (1, 0.2%), Cadidatus Rickettsia hongyuanensis (4, 0.9%), Ca. R. jingxinensis (11, 2.6%), Ca. R. vulgarisii (11, 2.6%) and Anaplasma ovis (98, 23.1%). The positive rate of bacterial species ranged from 0.2% to 24.0%. Interestingly, one novel Rickettsia species, provisionally named "Candidatus Rickettsia vulgarisii", was detected in Argas ticks from Zhongwei city, which suggests the possibility of local transmission to other areas through birds. Genetic and phylogenetic analysis based on the 16S rRNA, gltA, ompA, and 17kDa genes indicated that it was divergent from all known SFG Rickettsia species but mostly related to R. vini. Different SFGR species were associated with specific tick species or genera. In addition, Anaplasma ovis was detected in two Dermacentor species, and co-infection with SFGRs was observed in 14.6% (62/425) of samples.

CONCLUSIONS

This study describes the prevalence and diversity of SFGRs in ticks from Ningxia for the first time by direct detection, reveals that Rickettsia diversity related to tick species. This data suggests that surveillance for tick-borne SFGR infections among human populations should be enhanced in this region, and further investigations on their pathogenicity to humans and domestic animals are still needed.

Morphological and Molecular Characterization of Tick Species Infesting Cattle in South Africa

Ticks are a significant threat to livestock globally, with certain species displaying distinct host preferences at various developmental stages. Accurate species-level identification is essential for studying tick populations, implementing control strategies, and understanding disease dynamics. This study evaluated ticks infesting cattle across six provinces in South Africa using morphological and molecular methods. Ticks were preserved, examined morphologically using an Olympus Digital Camera Microscope, and identified using the 16S rRNA gene. The study identified four genera, namely Amblyomma, Hyalomma, Ixodes, and Rhipicephalus, comprising 15 ixodid species. Amblyomma hebraeum was the most prevalent species, with an infestation rate of 54.4%. Molecular analysis revealed genetic relationships among tick species, with genetic distances ranging from 0.00 to 0.13, and phylogenetic analysis clustered species into distinct genera with high bootstrap support. Principal Component Analysis highlighted clear genetic relatedness among species. These findings enhance our understanding of tick diversity, morphology, and distribution in South Africa's cattle populations, emphasizing their economic significance. The study provides critical baseline data for monitoring and developing effective strategies to manage tick-borne diseases, ensuring improved livestock health and productivity.

Involvement of a Microplusin-like Gene (HlonML-1) in the Olfactory Chemosensation of Haemophysalis longicornis: Expression, RNA Silencing, and Behavioral Implications

The study of tick olfaction is relatively new compared to that of insects, and the molecular mechanisms involved remain poorly understood. Despite several potential chemosensory genes identified in multiple tick species, these are yet to be validated through independent functional experiments. In this research, we cloned and analyzed a microplusin-like gene, HlonML-1, and investigated its role in the chemosensory activities of H. longicornis. The results showed that this gene's amino acid sequences lack histidine residues essential for antimicrobial activity, and it is evolutionarily linked to putative chemosensory microplusins in ticks. Gene expression analyses indicated that HlonML-1 was significantly more abundant in ticks exposed to potential attractants and in the forelegs of H. longicornis than in non-exposed ticks and the hindlegs, respectively. Tick forelegs support the Haller's organ, which is a sensory structure mostly specialized for chemosensation. Furthermore, Y-tube olfactometer assays indicated that silencing HlonML-1 significantly impaired adult ticks' ability to detect selected odors, while their gustatory-related behavior remained unaffected compared to the control groups. Given its unique sequences, relative abundance in chemosensory tissues, and impact on odor detection, HlonML-1 is likely involved in the olfactory chemosensation of H. longicornis. Future research validating putative chemosensory microplusins in the genomes of various tick species may enhance our understanding of their olfactory functions in tick and lead to the identification of new molecular targets for developing tick repellents.

Extrinsic and intrinsic drivers of prevalence and abundance of hard-bodied ticks (Acari: Ixodidae) in one-humped camel (Camelus dromedarius)

Background

Ticks are ectoparasites and can be vectors of a wide range of pathogens, posing significant health risks to livestock. In the Sahara Desert of Algeria, particularly among one-humped camels (Camelus dromedarius), there is a need to better understand the factors influencing tick infestation patterns to improve livestock management and health outcomes.

Objectives

This study aimed to investigate the prevalence, intensity, and abundance of hard-bodied ticks (Acari: Ixodidae) among dromedaries, examining both intrinsic factors (sex, age, coat color) and extrinsic variables (farming systems, vegetation types, climate zones, and elevation) that might influence tick infestation in this region.

Methods

Ticks were collected from 286 dromedaries across nine sites in the pre-Saharan regions of Algeria, with elevations ranging from 736 m to 980 m. The sampled camels, which ranged in age from 6 days to 21 years, were examined for tick infestations. The ticks were identified through macroscopic and microscopic methods, and their abundance was analyzed in relation to the camels' characteristics and environmental factors. Three breeding systems were recognized: extensive, intensive, and mixed.

Results

A total of 980 ticks were collected, with Hyalomma dromedarii Koch, 1844 being the most abundant species (553 specimens), followed by Hyalomma impeltatum Schulze & Schlottke, 1930 (393 specimens), and Hyalomma excavatum Koch, 1844 (34 specimens). H. dromedarii showed a preference for parasitizing brown-coated dromedaries and exhibited significantly higher infestation levels during spring (p < 0.001). No significant association was observed between tick infestation and the camels' age or sex (p > 0.05). However, the farming system had a significant impact on tick abundance, with extensive and mixed systems showing higher tick burdens compared to intensive systems (p < 0.01). Additionally, the vegetation type, climate zone, and foraging habitat elevation were found to significantly influence tick densities and prevalence.

Conclusion

This study provides essential insights into the tick infestation dynamics in dromedaries in drylands of Algeria. It highlights the influence of coat color, seasonality, and farming practices on tick burden, with brown-coated camels being more susceptible during the spring. The findings underline the importance of considering both intrinsic and extrinsic factors when developing effective tick control strategies, especially for camels raised in extensive or mixed farming systems in diverse arid rangelands. Future research should expand the scope to cover other arid regions in North Africa for a comprehensive understanding of tick-host dynamics.

Genetic diversity of tick-borne zoonotic pathogens in ixodid ticks collected from small ruminants in Northern Pakistan

Mapping tick distribution and pathogens in unexplored areas sheds light on their importance in zoonotic and veterinary contexts. In this study, we performed a comprehensive investigation of the genetic diversity of tick and tick-borne pathogens (TBPs) detection infesting/infecting small ruminants across northern Pakistan. We collected 1587 ixodid ticks from 600 goats and sheep, an overall tick infestation rate of 50.2 %. Notably, gender-based infestation rates were higher in female goats and sheep compared to their male counterparts. Age-wise analysis showed that the tick infestation rate was higher in older animals. This study identified 11 ixodid tick species within three genera: Hyalomma, Haemaphysalis, and Rhipicephalus, which were taxonomically classified using 16S rRNA and cytochrome oxidase I (cox1) molecular markers. Sequence analysis indicated that reported ticks are similar to ixodid species found across various Asian and African countries. Tick-borne pathogens were detected by amplifying 16S rRNA and citrate synthase (gltA) for bacterial pathogens and 18S rRNA for apicomplexan parasites. The present study reported a diverse array of TBPs in ticks from the study area, with Rickettsia massiliae (24.5 %) and Theleria ovis (16.4 %) as the most prevalent bacterial and apicomplexan pathogens. Phylogenetically, detected TBPs shared evolutionary relatedness with identical TBPs from old and new world countries. These findings highlight the presence of zoonotic TBPs in ixodid ticks from Pakistan. In addition, it also provides a foundation for future epidemiological research on ticks and TBPs, emphasizing their relevance in both zoonotic and veterinary contexts.

The contact toxicity and toxic mechanism of essential oils from Pimenta racemosa and Eugenia caryophyllata against Haemaphysalis longicornis (Acari: Ixodidae)

Haemaphysalis longicornis, which is widely distributed in China, can transmit various tick-borne diseases such as severe fever with thrombocytopenia syndrome, babesiosis, rickettsia disease and so on, and do great harm to human health and the development of animal husbandry. Chemical acaricides are the most traditional tick control method, but because of its many shortcomings, there is an urgent need to find a substitute with high efficiency, environmental protection and low toxicity. It has been found that some plant essential oils (EOs) have good insecticidal activity and environmental safety. In this study, the components of EOs from Pimenta racemosa and Eugenia caryophyllata were analyzed by gas chromatography-mass spectrometry (GC-MS), and their potential for application in the control of Haemaphysalis longicornis were studied. Gas chromatography-mass spectrometry analysis showed that the main components of P. racemosa EO were eugenol (64.07%), those of E. caryophyllata EO were Hexadecanoic acid, 2-methylpropyl ester (51.84%) and eugenol (39.76%). Larval packet test showed that the EOs of P. racemosa and E. caryophyllata had significant acaricidal activity against unfed larvae of H. longicornis, with LC50 values of 1.20 mg/mL and 0.47 mg/mL and LC90 values of 8.76 mg/mL and 2.91 mg/mL, respectively. The P. racemosa EO, E. caryophyllata EO and eugenol showed significant acaricidal activity against unfed nymph H. longicornis, with LC50 values of 1.65 mg/mL, 2.29 mg/mL and 0.93 mg/mL and LC90 values of 5.03 mg/mL, 11.01 mg/mL and 4.77 mg/mL, respectively. The P. racemosa EO, E. caryophyllata EO and eugenol showed significant acaricidal activity against unfed adults H. longicornis, with LC50 values of 0.51 mg/mL, 2.57 mg/mL and 1.83 mg/mL and LC90 values of 2.44 mg/mL, 11.44 mg/mL and 2.54 mg/mL, respectively. Enzyme assays revealed that the E. caryophyllata EO and eugenol significantly inhibited the activity of carboxylesterase (CarE), eugenol significantly inhibited the activity of catalase (CAT), and two EOs and eugenol had no significant effect on acetylcholinesterase (AchE) (p < 0.05). The above results suggest that the essential oils from P. racemosa and E. caryophyllata have great potential for use as alternatives to synthetic acaricides for tick control.

RNA viromes of Dermacentor nuttalli ticks reveal a novel uukuvirus in Qīnghăi Province, China

Ticks are a major parasite on the Qīnghăi-Tibet Plateau, western China, and represent an economic burden to agriculture and animal husbandry. Despite research on tick-borne pathogens that threaten humans and animals, the viromes of dominant tick species in this area remain unknown. In this study, we collected Dermacentor nuttalli ticks near Qīnghăi Lake and identified 13 viruses belonging to at least six families through metagenomic sequencing. Four viruses were of high abundance in pools, including Xīnjiāng tick-associated virus 1 (XJTAV1), and three novel viruses: Qīnghăi Lake virus 1, Qīnghăi Lake virus 2 (QHLV1, and QHLV2, unclassified), and Qīnghăi Lake virus 3 (QHLV3, genus Uukuvirus of family Phenuiviridae in order Bunyavirales), which lacks the M segment. The minimum infection rates of the four viruses in the tick groups were 8.2%, 49.5%, 6.2%, and 24.7%, respectively, suggesting the prevalence of these viruses in D. ​nuttalli ticks. A putative M segment of QHLV3 was identified from the next-generation sequencing data and further characterized for its signal peptide cleavage site, N-glycosylation, and transmembrane region. Furthermore, we probed the L, M, and S segments of other viruses from sequencing data of other tick pools by ​using the putative M segment sequence of QHLV3. By revealing the viromes of D. nuttalli ticks, this study enhances our understanding of tick-borne viral communities in highland regions. The putative M segment identified in a novel uukuvirus suggests that previously identified uukuviruses without M segments should have had the same genome organization as typical bunyaviruses. These findings will facilitate virus discovery and our understanding of the phylogeny of tick-borne uukuviruses.

Hard Ticks as Vectors: The Emerging Threat of Tick-Borne Diseases in India

Hard ticks (Ixodidae) play a critical role in transmitting various tick-borne diseases (TBDs), posing significant global threats to human and animal health. Climatic factors influence the abundance, diversity, and vectorial capacity of tick vectors. It is imperative to have a comprehensive understanding of hard ticks, pathogens, eco-epidemiology, and the impact of climatic changes on the transmission dynamics of TBDs. The distribution and life cycle patterns of hard ticks are influenced by diverse ecological factors that, in turn, can be impacted by changes in climate, leading to the expansion of the tick vector's range and geographical distribution. Vector competence, a pivotal aspect of vectorial capacity, involves the tick's ability to acquire, maintain, and transmit pathogens. Hard ticks, by efficiently feeding on diverse hosts and manipulating their immunity through their saliva, emerge as competent vectors for various pathogens, such as viruses, parasites and bacteria. This ability significantly influences the success of pathogen transmission. Further exploration of genetic diversity, population structure, and hybrid tick vectors is crucial, as they play a substantial role in influencing vector competence and complicating the dynamics of TBDs. This comprehensive review deals with important TBDs in India and delves into a profound understanding of hard ticks as vectors, their biology, and the factors influencing their vector competence. Given that TBDs continue to pose a substantial threat to global health, the review emphasizes the urgency of investigating tick control strategies and advancing vaccine development. Special attention is given to the pivotal role of population genetics in comprehending the genetic diversity of tick populations and providing essential insights into their adaptability to environmental changes.

Molecular characterization and induced changes of histone acetyltransferases in the tick Haemaphysalis longicornis in response to cold stress

BACKGROUND

Epigenetic modifications of histones play important roles in the response of eukaryotic organisms to environmental stress. However, many histone acetyltransferases (HATs), which are responsible for histone acetylation, and their roles in mediating the tick response to cold stress have yet to be identified. In the present study, HATs were molecularly characterized and their associations with the cold response of the tick Haemaphysalis longicornis explored.

METHODS

HATs were characterized by using polymerase chain reaction (PCR) based on published genome sequences, followed by multiple bioinformatic analyses. The differential expression of genes in H. longicornis under different cold treatment conditions was evaluated using reverse transcription quantitative PCR (RT-qPCR). RNA interference was used to explore the association of HATs with the cold response of H. longicornis.

RESULTS

Two HAT genes were identified in H. longicornis (Hl), a GCN5-related N-acetyltransferase (henceforth HlGNAT) and a type B histone acetyltransferase (henceforth HlHAT-B), which are respectively 960 base pairs (bp) and 1239 bp in length. Bioinformatics analysis revealed that HlGNAT and HlHAT-B are unstable hydrophilic proteins characterized by the presence of the acetyltransferase 16 domain and Hat1_N domain, respectively. RT-qPCR revealed that the expression of HlGNAT and HlHAT-B decreased after 3 days of cold treatment, but gradually increased with a longer period of cold treatment. The mortality rate following knockdown of HlGNAT or HlHAT-B by RNA interference, which was confirmed by RT-qPCR, significantly increased (P < 0.05) when H. longicornis was treated at the lowest lethal temperature (- 14 °C) for 2 h.

CONCLUSIONS

The findings demonstrate that HATs may play a crucial role in the cold response of H. longicornis. Thus further research is warranted to explore the mechanisms underlying the epigenetic regulation of the cold response in ticks.

Sequential expression of small heat shock proteins contributing to the cold response of Haemaphysalis longicornis (Acari: Ixodidae)

BACKGROUND

Haemaphysalis longicornis is an important livestock pest and a serious threat to public health. Cold is a common form of stress affecting its survival and distribution. However, H. longicornis exhibits different physiological responses to cold stress. In this study, we systematically explored the regulation and functions of small heat shock proteins (sHsps) in H. longicornis during cold stress.

RESULTS

Seven sHsp genes (HlsHsp14.9, HlsHsp19.9, HlsHsp20.3, HlsHsp21.4, HlsHsp23.7, HlsHsp24.0, and HlsHsp26.1) with open reading frame lengths ranging from 408 bp (HlsHsp14.9) to 673 bp (HlsHsp26.1) were cloned from H. longicornis, and featured the typical α-crystallin domain. Phylogenetic analysis revealed high similarity with the sHsps of arachnid species. Quantitative polymerase chain reaction analysis revealed that the regulation of sHsp genes depended on the severity and duration of cold treatment. Moreover, the relative expression of each gene was largely dependent on the treatment period (P < 0.01; 3, 6, and 9 days of treatment at 8, 4, 0, and -4 °C). Among all genes, HlsHsp14.9, HlsHsp19.9, HlsHsp20.3, and HlsHsp24.0 were most sensitive to rapid cold treatment. After RNA interference, the mortality of H. longicornis was significantly increased at -14 °C (P < 0.05), suggesting that the expression of sHsp genes is closely related to cold tolerance in H. longicornis.

CONCLUSION

Our results indicate that sHsps play an important role in the cold stress response of H. longicornis, which may enhance our understanding of the cold adaptation mechanisms in ticks. © 2023 Society of Chemical Industry.

First Molecular Identification of Rickettsia aeschlimannii and Rickettsia africae in Ticks from Ghana

The threats from vector-borne pathogens transmitted by ticks place people (including deployed troops) at increased risk for infection, frequently contributing to undifferentiated febrile illness syndromes. Wild and domesticated animals are critical to the transmission cycle of many tick-borne diseases. Livestock can be infected by ticks, and serve as hosts to tick-borne diseases such as rickettsiosis. Thus, it is necessary to identify the tick species and determine their potential to transmit pathogens. A total of 1,493 adult ticks from three genera-Amblyomma, Hyalomma, and Rhipicephalus-were identified using available morphological keys and were pooled (n = 541) by sex and species. Rickettsia species were detected in 308 of 541 (56.9%) pools by genus-specific quantitative polymerase chain reaction assay (Rick17b). Furthermore, sequencing of the outer membrane protein A and B genes (ompA and ompB) of random samples of Rickettsia-positive samples led to the identification of Rickettsia aeschlimannii and Rickettsia africae with most R. africae DNA (80.2%) detected in pools of Amblyomma variegatum. We report the first molecular detection and identification of the rickettsial pathogens R. africae and R. aeschlimannii in ticks from Ghana. Our findings suggest there is a need to use control measures to prevent infections from occurring among human populations in endemic areas in Ghana. This study underscores the importance of determining which vector-borne pathogens are in circulation in Ghana. Further clinical and prevalence studies are needed to understand more comprehensively the clinical impact of these rickettsial pathogens contributing to human disease and morbidity in Ghana.

Molecular Identification of Babesia and Theileria Infections in Livestock in the Qinghai-Tibetan Plateau Area, China

The northwestern region of China, known as the Qinghai-Tibet Plateau Area (QTPA), is characterized by unique climate conditions that support the breeding of various highly-adapted livestock species. Tick vectors play a significant role in transmitting Babesia and Theileria species, posing serious risks to animal health as well as the economy of animal husbandry in QTPA. A total of 366 blood samples were collected from Tibetan sheep (n = 51), goats (n = 67), yaks (n = 43), cattle (n = 49), Bactrian camels (n = 50), horses (n = 65), and donkeys (n = 40). These samples were examined using conventional and nested PCR techniques to detect Theileria and Babesia species. The overall infection rates were 0.3% (1/366) for Babesia spp. and 38.2% (140/366) for Theileria spp. Notably, neither Babesia nor Theileria species were detected in donkeys and yaks. The infection rates of Babesia and Theileria species among animals in different prefectures were significantly different (p < 0.05). Furthermore, Babesia bovis, B. bigemina, B. caballi, and B. ovis were not detected in the current study. To our knowledge, this is the first documented detection of Theileria luwenshuni infection in Bactrian camels and goats, as well as T. sinesis in cattle and T. equi in horses on the Qinghai plateau. These novel findings shed light on the distribution of Babesia and Theileria species among livestock species in QTPA.

Revealing the Diversity of the Mycobiome in Different Phases of Ticks: ITS Gene-Based Analysis

Ticks are obligate ectoparasites and vectors of a variety of pathogens in humans and animals. Certain tick-borne pathogens (TBPs) have been identified as the cause of zoonoses, posing potentially significant threats to the human health and livestock industries. Fungi are one of the major TBPs that can affect ticks and cause disease in humans. At present, there are few studies on the diversity of fungal microbial communities carried by Ixodes. Therefore, profiling tick-borne fungi will contribute to understanding the tick-fungal interaction. This study evaluated the community profile and differences in the fungal microbiome in Ixodidae collected on parasitic ticks or nonparasitic ticks in Wuwei, Gansu Province, China. The Shannon index, Simpson index, and Richness index were used to evaluate the diversity of mycobiome. Principle coordinates analysis (PCoA) was conducted to determine patterns of diversity in mycobiome. Using correlation analysis to determine the correlation of mycobiome. The results show that the high-throughput sequencing of the internal transcribed spacer gene generated 3,634,943 raw reads and 7,482 amplicon sequence variants. The dominant tick species in this region was Dermacentor nuttalli (Ixodidae). The mycobiome belonged to four classes-Dothideomycetes, Sordariomycetes, Ustilaginomycetes, and Tremellomycetes-and more than 261 genera, the most abundant genera were Cladosporium, Purpureocillium, Aureobasidium, Tranzscheliella, and Sporormiella. Alpha diversity indicated that the abundance and evenness of mycobiome were marginally higher in nonparasitic ticks than in parasitic ticks. PCoA showed that the community structures of parasitic ticks vary from nonparasitic ticks, samples from nonparasitic ticks tended to cluster more closely than those from the parasitic ticks. Correlation analysis indicated that there was a significant positive correlation or negative correlation between the mycobiome. Our results indicate that the mycobiome carried by Dermacentor nuttalli had rich diversity, and there was a significant difference in mycobiome between parasitic ticks and nonparasitic ticks. These findings may conducive to understand the complex interaction between ticks and commensal fungi and provide help for the further exploration of the behavioral characteristics of ticks and formulation of effective biological control measures.

Evidence-practice gap analysis in the role of tick in brucellosis transmission: a scoping review

BACKGROUND

Brucellosis is a zoonotic affliction instigated by bacteria belonging to the genus Brucella and is characterized by a diverse range of pervasiveness, multiple transmission routes, and serious hazards. It is imperative to amalgamate the current knowledge and identify gaps pertaining to the role of ticks in brucellosis transmission.

METHODS

We systematically searched China National Knowledge Infrastructure (CNKI), WanFang, Google Scholar, and PubMed on the topic published until April 23, 2022. The procedure was performed in accordance with the Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. The selected articles were categorized across three major topic areas, and the potential data was extracted to describe evidence-practice gaps by two reviewers.

RESULTS

The search identified 83 eligible studies for the final analyses. The results highlighted the potential capacity of ticks in brucellosis transmission as evidenced by the detection of Brucella in 16 different tick species. The pooled overall prevalence of Brucella in ticks was 33.87% (range: 0.00-87.80%). The review also revealed the capability of Brucella to circulate in parasitic ticks' different developmental stages, thus posing a potential threat to animal and human health. Empirical evidence from in vitro rodent infection experiments has revealed that ticks possess the capability to transmit Brucella to uninfected animals (range: 45.00-80.00%). Moreover, significant epidemiological associations have been found between the occurrence of brucellosis in animals and tick control in rangelands, which further suggests that ticks may serve as potential vectors for brucellosis transmission in ruminants. Notably, a mere three cases of human brucellosis resulting from potential tick bites were identified in search of global clinical case reports from 1963 to 2019.

CONCLUSIONS

It is imperative to improve the techniques used to identify Brucella in ticks, particularly by developing a novel, efficient, precise approach that can be applied in a field setting. Furthermore, due to the lack of adequate evidence of tick-borne brucellosis, it is essential to integrate various disciplines, including experimental animal science, epidemiology, molecular genetics, and others, to better understand the efficacy of tick-borne brucellosis. By amalgamating multiple disciplines, we can enhance our comprehension and proficiency in tackling tick-borne brucellosis.

Microbial diversity of ticks and a novel typhus group Rickettsia species (Rickettsiales bacterium Ac37b) in Inner Mongolia, China

Ticks can carry multiple pathogens, and Inner Mongolia's animal husbandry provides excellent environmental conditions for ticks. This study characterized the microbiome of ticks from different geographical locations in Inner Mongolia; 905 Dermacentor nuttalli and 36 Ixodes persulcatus were collected from sheep in three main pasture areas and from bushes within the forested area. Mixed DNA samples were prepared from three specimens from each region and tick species. Microbial diversity was analyzed by 16S rRNA sequencing, and α and β diversity were determined. The predominant bacterial genera were Rickettsia (54.60%), including Rickettsiales bacterium Ac37b (19.33%) and other Rickettsia (35.27%), Arsenophonus (11.21%), Candidatus Lariskella (10.84%), and Acinetobacter (7.17%). Rickettsia bellii was identified in I. persulcatus, while Rickettsiales bacterium Ac37b was found in D. nuttalli from Ordos and Chifeng. Potential Rickettsia and Anaplasma coinfections were observed in the Ordos region. Tick microbial diversity analysis in Inner Mongolia suggests that sheep at the sampling sites were exposed to multiple pathogens.

Repellent effects of Chinese cinnamon oil on nymphal ticks of Haemaphysalis longicornis, Rhipicephalus haemaphysaloides, and Hyalomma asiaticum

The repellent activity of Chinese cinnamon oil (Cinnamomum cassia) on nymphal ticks (Haemaphysalis longicornis Neumann, Rhipicephalus haemaphysaloides Supino, and Hyalomma asiaticum Schulze and Schlottke) was evaluated in a sample Y-tube bioassay. The results were based on the vertical migration of ticks during the host-seek phase and showed a dose-dependent repellent effect of Chinese cinnamon oil on the tested nymphs after 6 h. For H. longicornis, R. haemaphysaloides, and H. asiaticum at the concentrations (vol/vol) of 3, 3, and 1.5%, the repellent percentages over time were 68-97, 69-94, and 69-93%, respectively, which indicated strong repellent activities against ticks, similar to the positive control DEET (N,N-diethyl-3-methylbenzamide). Chinese cinnamon oil exerted the strongest effect on H. asiaticum nymphs. To our knowledge, this is the first study to investigate the repellent effects of Chinese cinnamon oil on ticks. Chinese cinnamon oil has considerable potential and should be developed as a practical tick repellent.

Characterization of the bacterial microbiota of cattle ticks in northeastern Thailand through 16S rRNA amplicon sequencing

Ticks are vectors of a variety of pathogens that can infect humans and animals. Ticks also harbor non-pathogenic microbiota. This study characterized the microbiota of the ticks infesting beef cattle in Thailand. Two species of ticks; Rhipicephalus microplus (n = 15) and Haemaphysalis bispinosa (n = 5), were collected in seven provinces in northeastern Thailand. Microbial community profile of ticks was examined based on sequences of the V3-V4 region of 16S rRNA gene. Proteobacteria (Pseudomonadota) was the most abundant phylum, followed by Firmicutes (Bacillota), and Actinobacteriota. Coxiella-like endosymbiont was the most abundant bacterial taxon overall (49% of sequence reads), followed by Anaplasma (8.5%), Corynebacterium (5.5%), Ehrlichia (3.9%), and Castellaniella (3.4%). Co-infections of the pathogenic bacteria Ehrlichia and Anaplasma were detected in 19/20 (95%) female ticks. The tick with the lowest number of bacteria had the lowest abundance of the Coxiella-like endosymbiont, and the pathogenic bacteria Anaplasma and Ehrlichia were absent. This study provides baseline information of the microbiota of cattle ticks in northeastern Thailand, suggesting that ticks carry a few dominant bacterial taxa that are primarily non-pathogenic but can co-occur with pathogenic microorganisms. The information obtained is useful for monitoring disease outbreaks in the future and informing prevention and control strategies against cattle tick-borne diseases.

Molecular characterization and modulated expression of histone acetyltransferases during cold response of the tick Dermacentor silvarum (Acari: Ixodidae)

BACKGROUND

Histone acetylation is involved in the regulation of stress responses in multiple organisms. Dermacentor silvarum is an important vector tick species widely distributed in China, and low temperature is a crucial factor restricting the development of its population. However, knowledge of the histone acetyltransferases and epigenetic mechanisms underlying cold-stress responses in this tick species is limited.

METHODS

Histone acetyltransferase genes were characterized in D. silvarum, and their relative expressions were determined using qPCR during cold stress. The association and modulation of histone acetyltransferase genes were further explored using RNA interference, and both the H3K9 acetylation level and relative expression of KAT5 protein were evaluated using western blotting.

RESULTS

Three histone acetyltransferase genes were identified and named as DsCREBBP, DsKAT6B, and DsKAT5. Bioinformatics analysis showed that they were unstable hydrophilic proteins, characterized by the conserved structures of CBP (ZnF_TAZ), PHA03247 super family, Creb_binding, and MYST(PLN00104) super family. Fluorescence quantitative PCR showed that the expression of DsCREBBP, DsKAT6B, and DsKAT5 increased after 3 days of cold treatment, with subsequent gradual decreases, and was lowest on day 9. Western blotting showed that both the H3K9 acetylation level and relative expression of KAT5 in D. silvarum increased after treatment at - 4, 4, and 8 °C for 3 and 6 days, whereas they decreased significantly after a 9-day treatment. RNA interference induced significant gene silencing, and the mortality rate of D. silvarum significantly increased at the respective semi-lethal temperatures.

CONCLUSION

These results imply that histone acetyltransferases play an important role in tick adaptation to low temperatures and lay a foundation for further understanding of the epigenetic regulation of histone acetylation in cold-stressed ticks. Further research is needed to elucidate the mechanisms underlying histone acetylation during cold stress in ticks.

Circulation of multiple Rickettsiales bacteria in ticks from Sichuan province, Southwest China

During 2021, 403 ticks including Haemaphysalis qinghaiensis, Ixodes ovatus, Ixodes acutitarsus, and Rhipicephalus microplus were collected from three sites (590, 310, and 576 km away from each other) in Sichuan Province, China. A total of nine Rickettsiales species were identified in them, including three Rickettsia spp., five Anaplasma spp., and one Ehrlichia sp. Anaplasma ovis and a novel Rickettsia sp. named "Candidatus Rickettsia liangshanensis" were characterized in I. ovatus ticks from Liangshan, with positive rates of 11.11% and 45.56%, respectively. Anaplasma capra (13.33%) and Anaplasma bovis (15.33%) were detected in H. qinghaiensis ticks from Maerkang. Phylogenetic analysis based on 16S rRNA, gltA, and groEL gene sequences indicated that the A. bovis strains were divided into two groups. Additionally, a novel Ehrlichia species named "Candidatus Ehrlichia maerkangensis" was identified. It is closely related to "Candidatus Ehrlichia zunyiensis" which was previously reported in Berylmys bowersi rats from Zunyi City, Southwest China. In R. microplus from Mianyang, "Candidatus Rickettsia jingxinensis" was detected with a high prevalence (92.99%). Notably, a variant of R. raoultii was identified in I. acutitarsus (33.33%). This may be the first Rickettsiales bacterium reported in I. acutitarsus. Our results reveal the remarkable biodiversity of Rickettsiales in this area. Some of these bacteria are human pathogens, indicating the potential exposure risk to local people.

The genome-wide characterization and associated cold-tolerance function of the superoxide dismutase in the cold response of the tick Haemaphysalis longicornis

Accumulating evidence suggests that superoxide dismutase (SOD) is the first line of antioxidant defense in organisms and plays an important role in scavenging reactive oxygen species produced during environmental stress. However, limited information is available regarding the response of SOD genes to cold stress in ticks. Therefore, in the present study, SOD genes were cloned and identified from the genome of Haemaphysalis longicornis, and the function of SOD during the cold response was further explored. Seven SOD genes were characterized: HlCCS1, HlCCS2, HlMSD, HlCSD1, HlCSD2, HlCSD3, and HlCSD4. Bioinformatics analysis showed that HlCCS1 and HlCCS2 are copper chaperones of SODs. HlCSD1-HlCSD4 belong to the Cu/Zn SOD, whereas HlMSD belongs to the Mn SOD gene family. Fluorescence quantitative PCR showed that the expression of HlCCS2, HlMSD, and HlCSD1-3 was upregulated, whereas HlCCS1 and HlCSD4 were downregulated during the cold response of H. longicornis. Western blotting confirmed changes in the relative expression of HlCSD3 and HlMSD in H. longicornis after cold treatment. Mortality of H. longicornis increased significantly after dsRNA injection of HlCCS2, HlMSD, HlCSD1, and HlCSD3. The above results show that SODs have different regulatory functions during the cold response in H. longicornis, and there might be an interaction between treatment temperature and duration. Furthermore, the results lay a foundation for subsequent research on the molecular mechanism of cold tolerance in H. longicornis and shed light on the population distribution and diffusion limit of ticks.

HARD TICKS (ACARI: IXODIDAE) INFESTING ARABIAN CAMELS (CAMELUS DROMEDARIUS) IN MEDINA AND QASSIM, SAUDI ARABIA

Ixodid ticks are hematophagous obligatory ectoparasites that occur worldwide and transmit pathogens to humans and other vertebrates, causing economic livestock losses. The Arabian camel (Camelus dromedarius Linnaeus, 1758) is an important livestock animal in Saudi Arabia that is vulnerable to parasitism by ticks. The diversity and intensity of ticks on Arabian camels in certain localities in the Medina and Qassim regions of Saudi Arabia were determined. One hundred forty camels were examined for ticks, and 106 were infested (98 females, 8 males). A total of 452 ixodid ticks (267 males, 185 females) were collected from the infested Arabian camels. The tick infestation prevalence was 83.1% and 36.4% in female and male camels, respectively (female camels harbored significantly more ticks than did male camels). The recorded tick species were Hyalomma dromedarii Koch, 1844 (84.5%); Hyalomma truncatum Koch, 1844 (11.1%); Hyalomma impeltatum Schulze and Schlottke, 1929 (4.2%); and Hyalomma scupense Schulze, 1919 (0.22%). Hyalomma dromedarii was the predominant tick species in most regions, with a mean intensity of 2.15 ± 0.29 ticks/camel (2.5 ± 0.53 male ticks/camel, 1.8 ± 0.21 female ticks/camel). The proportion of male ticks was higher than that of female ticks (59.1 vs. 40.9%). To the best of our knowledge, this is the first survey of ixodid ticks on Arabian camels in Medina and Qassim, Saudi Arabia.

Anaplasma Species in Ticks Infesting Mammals of Sardinia, Italy

Ticks are hematophagous ectoparasites that are recognized for their ability to vector a wide variety of pathogens of viral, bacterial, protozoal, and helminthic nature to vertebrate hosts. Among the different diseases transmitted by ticks, also called "Tick-Borne Diseases" (TBD), many are zoonotic. Pathogens of the genus Anaplasma refer to obligate intracellular bacteria within the Rickettsiales order transmitted mainly through tick bites and considered as well-established threats to domestic animals, livestock, and humans, worldwide. In this retrospective study, 156 ticks collected from twenty goats, one marten, and one cattle from several Sardinian sites, were examined by molecular analyses to detect the presence of Anaplasma species. A total of 10 (10/156; 6.4%) ticks were shown to be Anaplasma-positive by PCR screening. After sequence analyses, A. phagocytophilum was detected in four Rhipicephalus sanguineus s.l. (3.3%) and four Rh. bursa (11%) ticks from goats, while one Rh. sanguineus s.l. (0.8%) and one Rh. bursa (2.8%) collected from the marten and cattle, respectively, exhibited 100% of identity with A. marginale strains. In this study, we provide the first description and molecular detection of A. marginale and A. phagocytophilum in ticks of the Rhiphicephalus genus in Sardinia. Considering the growing impact of tick-borne Anaplasma pathogens on human health, further studies are necessary to monitor the prevalence of these pathogens in Sardinia.

Diversity of Rickettsiales bacteria in five species of ticks collected from Jinzhai County, Anhui Province, China in 2021-2022

The order Rickettsiales in the class Alphaproteobacteria comprises vector-borne pathogens of both medical and veterinary importance. Ticks, as a group, are second only to mosquitoes as vectors of pathogens to humans, playing a critical role in the transmission of rickettsiosis. In the present study, 880 ticks collected from Jinzhai County, Lu'an City, Anhui Province, China in 2021-2022 were identified as belonging to five species from three genera. DNA extracted from individual ticks was examined using nested polymerase chain reaction targeting the 16S rRNA gene (rrs), and the gene fragments amplified were sequenced to detect and identify Rickettsiales bacteria in the ticks. For further identification, the rrs-positive tick samples were further amplified by PCR targeting the gltA and groEL gene and sequenced. As a result, 13 Rickettsiales species belonging to the genera Rickettsia, Anaplasma, and Ehrlichia were detected, including three tentative species of Ehrlichia. Our results reveal the extensive diversity of Rickettsiales bacteria in ticks from Jinzhai County, Anhui Province. There, emerging rickettsial species may be pathogenic and cause under-recognized diseases. Detection of several pathogens in ticks that are closely related to human diseases may indicate a potential risk of infection in humans. Therefore, additional studies to assess the potential public health risks of the Rickettsiales pathogens identified in the present study are warranted.

Rickettsia sp. and Anaplasma spp. in Haemaphysalis longicornis from Shandong province of China, with evidence of a novel species "Candidatus Anaplasma Shandongensis"

Haemaphysalis longicornis is one of the most dominant and widespread tick species in China. This species mainly infests wild animals and occasionally attacks humans, and has been associated with the transmission of a variety of zoonotic pathogens including spotted fever group Rickettsia (SFGR), severe fever with thrombocytopenia syndrome virus (SFTSV), Anaplasma phagocytophilum, Babesia spp. and Theileria spp.. Although there are increasing reports of various pathogens associated with H. longicornis, some neglected pathogens in certain areas still need to be studied. In this study, a total of 171 H. longicornis ticks were collected from goats in three locations of Shandong Province, Eastern China (Zibo, Linyi, and Qingdao cities), and subsequently screened for the presence of Rickettsia, Anaplasma, and Ehrlichia bacteria. A total of four bacterial species were identified and characterized. "Candidatus Rickettsia jingxinensis" was detected in one tick specimen from Zibo city. Of 98 ticks from Linyi city, 63.27% (62/98) were tested positive for Anaplasma capra and 5.10% (5/98) were positive for Anaplasma bovis. Interestingly, a novel Anaplasma species was detected and characterized in one tick specimen from Zibo and one other from Linyi, respectively. Genetic and phylogenetic analysis based on the 16S, gltA, groEL, and msp4 genes indicated that it was divergent from all known Anaplasma species but mostly related to A. phagocytophilum and "Cadidatus Anaplasma boleense". Based on where it was first detected, we named it "Candidatus Anaplasma shandongensis".

Identification of Bacterial Communities and Tick-Borne Pathogens in Haemaphysalis spp. Collected from Shanghai, China

Ticks can carry and transmit a large number of pathogens, including bacteria, viruses and protozoa, posing a huge threat to human health and animal husbandry. Previous investigations have shown that the dominant species of ticks in Shanghai are Haemaphysalis flava and Haemaphysalis longicornis. However, no relevant investigations and research have been carried out in recent decades. Therefore, we investigated the bacterial communities and tick-borne pathogens (TBPs) in Haemaphysalis spp. from Shanghai, China. Ixodid ticks were collected from 18 sites in Shanghai, China, and identified using morphological and molecular methods. The V3-V4 hypervariable regions of the bacterial 16S rRNA gene were amplified from the pooled tick DNA samples and subject to metagenomic analysis. The microbial diversity in the tick samples was estimated using the alpha diversity that includes the observed species index and Shannon index. The Unifrac distance matrix as determined using the QIIME software was used for unweighted Unifrac Principal coordinates analysis (PCoA). Individual tick DNA samples were screened with genus-specific or group-specific nested polymerase chain reaction (PCR) for these TBPs and combined with a sequencing assay to confirm the results of the V3-V4 hypervariable regions of the bacterial 16S rRNA gene. We found H. flava and H. longicornis to be the dominant species of ticks in Shanghai in this study. Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria are the main bacterial communities of Haemaphysalis spp. The total species abundances of Proteobacteria, Firmicutes and Bacteroidetes, are 48.8%, 20.8% and 18.1%, respectively. At the level of genus analysis, H. longicornis and H. flava carried at least 946 genera of bacteria. The bacteria with high abundance include Lactobacillus, Coxiella, Rickettsia and Muribaculaceae. Additionally, Rickettsia rickettsii, Rickettsia japonica, Candidatus Rickettsia jingxinensis, Anaplasma bovis, Ehrlichia ewingii, Ehrlichia chaffeensis, Coxiella spp. and Coxiella-like endosymbiont were detected in Haemaphysalis spp. from Shanghai, China. This study is the first report of bacterial communities and the prevalence of some main pathogens in Haemaphysalis spp. from Shanghai, China, and may provide insights and evidence for bacterial communities and the prevalence of the main pathogen in ticks. This study also indicates that people and other animals in Shanghai, China, are exposed to several TBPs.

The toxicity of the monoterpenes from lemongrass is mitigated by the detoxifying symbiosis of bacteria and fungi in the tick Haemaphysalis longicornis

The entry mode of terpenes into the atmosphere is via volatilization of hydrocarbons from foliage over heavily forested areas besides entering the environment through surface water runoff. Some monoterpenes in essential oils are phytotoxins, acting as plant chemical defenses against bacteria or fungi infections and plant-eating insects. For organisms to survive, their enzymatic systems are activated in response to an assault by potentially harmful compounds. Certain bacterial and fungal genera have developed special abilities to transform toxic terpenes into less toxic derivatives. Here, we investigated the response of the bacterial and fungal community in Haemaphysalis longicornis exposed to Cymbopogon citratus (lemongrass) essential oil (EO) and citronellal. Sequencing of bacterial 16S rRNA and fungal ITS1 regions on an Illumina NovaSeq PE250 sequencing platform was performed for H. longicornis tick samples treated with 15 and 20 mg/mL of lemongrass essential oil and citronellal. The diversity recorded in samples treated with C. citratus EO was higher in comparison to those treated with citronellal but significantly lower in the control samples as reflected by the Shannon diversity index. All major H. longicornis bacterial phyla, including Proteobacteria (93.81 %), Firmicutes (2.58 %), and Bacteroidota (0.99 %) were detected. A switch of dominance from Coxiella to Pseudomonas, which has high biotransformation capacity, was observed in the bacterial community, whereas the phylum Ascomycota (Genera: Aspergillus, Archaeorhizomyces, Alternaria, and Candida) dominated in the fungal community indicating detoxifying symbiosis. Other significantly abundant bacterial genera include Ralstonia, Acinetobacter, Vibrio, and Pseudoalteromonas, while Ganoderma and Trichosporon (yeasts) spp. represented the fungi Basidiomycota. This study expanded the understanding of enzymatic modification of phytotoxic substances by microorganisms, which could provide deeper insights into the mitigation of harmful phytotoxins and the synthesis of eco-friendly derivatives for the control of ticks.

Mapping the risk distribution of Borrelia burgdorferi sensu lato in China from 1986 to 2020: a geospatial modelling analysis

Lyme borreliosis, recognized as one of the most important tick-borne diseases worldwide, has been increasing in incidence and spatial extent. Currently, there are few geographic studies about the distribution of Lyme borreliosis risk across China. Here we established a nationwide database that involved Borrelia burgdorferi sensu lato (B. burgdorferi) detected in humans, vectors, and animals in China. The eco-environmental factors that shaped the spatial pattern of B. burgdorferi were identified by using a two-stage boosted regression tree model and the model-predicted risks were mapped. During 1986−2020, a total of 2,584 human confirmed cases were reported in 25 provinces. Borrelia burgdorferi was detected from 35 tick species with the highest positive rates in Ixodes granulatus, Hyalomma asiaticum, Ixodes persulcatus, and Haemaphysalis concinna ranging 20.1%−24.0%. Thirteen factors including woodland, NDVI, rainfed cropland, and livestock density were determined as important drivers for the probability of B. burgdorferi occurrence based on the stage 1 model. The stage 2 model identified ten factors including temperature seasonality, NDVI, and grasslands that were the main determinants used to distinguish areas at high or low-medium risk of B. burgdorferi, interpreted as potential occurrence areas within the area projected by the stage 1 model. The projected high-risk areas were not only concentrated in high latitude areas, but also were distributed in middle and low latitude areas. These high-resolution evidence-based risk maps of B. burgdorferi was first created in China and can help as a guide to future surveillance and control and help inform disease burden and infection risk estimates.

The life cycle of Hyalomma scupense (Acari: Ixodidae) under laboratory conditions

The life cycle of Hyalomma scupense on rabbit hosts was investigated under laboratory conditions. Hy. scupense exhibited one- and two-host life cycles of 163.2 and 161.4 days, respectively. The incubation of eggs required an average period of 52 days, which was the longest period among the four developmental stages. The average time for pre-feeding of larvae was 3.5 days. It took 20 days for larvae to become engorged nymphs and 52.3 days to become engorged females. The duration of the pre-feeding, feeding, pre-oviposition, and oviposition stages of female adults was 2.3, 13.5, 27.5, and 27.9 days, respectively. The average weight of engorged females was 390.0 mg (ranging from 129.3 mg to 828.6 mg), which was 28.95 times the weight of unfed females. There was a positive relationship between the weight and the number of eggs laid by engorged females (r = 0.927). The reproductive efficiency index (REI) was 8.63.

Detection and phylogenetic analysis of tick-borne bacterial and protozoan pathogens in a forest province of eastern China

Ticks, as obligate blood-sucking ectoparasites, feed on a broad range of vertebrates and transmit a great diversity of pathogenic microorganisms. Some tick-borne pathogens (TBPs) are endemic in China, whereas epidemiological studies are limited in Jiangxi, a forest province located in eastern China. Here, we have determined the positivity rates of TBPs in humans, rodents, dogs, goats and ticks, and performed the molecular characterization of TBPs in Jiangxi province. We found a high positivity rate of TBPs in the collected samples, demonstrating 23 (12.92%) samples positive for more than one TBPs. Of those, 11 (6.18%) samples were positive for Rickettsia spp., six (3.37%) Ehrlichia spp./Anaplasma spp., one (0.56%) Bartonella spp., two (1.12%) Borrelia spp., and five (2.81%) Babesia spp. The positivity rates of TBPs varied among ticks, animals, and humans as follow: goats (14/37, 37.84%), ticks (8/35, 22.86%), and dogs (1/11, 9.09%). Humans and rodents were negative for TBP presence. Phylogenetic analyses of these TBP sequences revealed the presence of Rickettsia japonica, Ehrlichia minasensis, and an unclassified Babesia spp. in goats, and Anaplasma phagocytophilum, Borrelia valaisiana, and an unclassified Bartonella spp. in ticks. Furthermore, R. japonica infection was exclusively found in goats with the positivity rate of 29.73%. Our study is the first report of R. japonica in goats around the world. These findings suggest high TBP positivity rates among goats, ticks, and dogs, and diverse TBPs in goats and ticks in the studied sites. Therefore, our results underscore the urgent need to assess TBP-tick-vertebrate-environment interactions and the risk of tick borne disease exposure in humans in the future.

Metatranscriptomics Reveals the Diversity of the Tick Virome in Northwest China

Blood-sucking ticks are obligate parasites and vectors of a variety of human and animal viruses. Some tick-borne viruses have been identified as pathogens of infectious diseases in humans or animals, potentially imposing significant public health burdens and threats to the husbandry industry. Therefore, identifying the profiles of tick-borne viruses will provide valuable information about the evolution and pathogen ecology of tick-borne viruses. In this study, we investigated the viromes of parasitic ticks collected from the body surfaces of herbivores in Xinjiang Uyghur Autonomous Region and Inner Mongolia Autonomous Region of China, two regions in northwest China. By using a metatranscriptomic approach, 17 RNA viruses with high diversity in genomic organization and evolution were identified. Among them, nine are proposed to be novel species. The classified viruses belonged to six viral families, including Phenuiviridae, Rhabdoviridae, Peribunyaviridae, Lispiviridae, Chuviridae, and Reoviridae, and unclassified viruses were also identified. In addition, although some viruses from different sampling locations shared significant similarities, the abundance and diversity of viruses notably varied among the different collection locations. This study demonstrates the diversity of tick-borne viruses in Xinjiang and Inner Mongolia and provides informative data for further study of the evolution and pathogenicity of these RNA viruses. IMPORTANCE Ticks are widely distributed in pastoral areas in northwestern China and act as vectors that carry and transmit a variety of pathogens, especially viruses. Our study revealed the diversity of tick viruses in Xinjiang and Inner Mongolia and uncovered the phylogenetic relationships of some RNA viruses, especially the important zoonotic tick-borne severe fever with thrombocytopenia syndrome virus in Inner Mongolia. These data suggest a complex and diverse evolutionary history and potential ecological factors associated with pathogenic viruses. The pathogenicity of these tick-borne viruses currently remains unclear. Therefore, future research should focus on evaluating the transmissability and pathogenicity of these tick-borne viruses.

The diversity and evolutionary relationships of ticks and tick-borne bacteria collected in China

Background

Ticks (order Ixodida) are ectoparasites, vectors and reservoirs of many infectious agents affecting humans and domestic animals. However, the lack of information on tick genomic diversity leaves significant gaps in the understanding of the evolution of ticks and associated bacteria.

Results

We collected > 20,000 contemporary and historical (up to 60 years of preservation) tick samples representing a wide range of tick biodiversity across diverse geographic regions in China. Metagenomic sequencing was performed on individual ticks to obtain the complete or near-complete mitochondrial (mt) genome sequences from 46 tick species, among which mitochondrial genomes of 23 species were recovered for the first time. These new mt genomes data greatly expanded the diversity of many tick groups and revealed five cryptic species. Utilizing the same metagenomic sequence data we identified divergent and abundant bacteria in Haemaphysalis, Ixodes, Dermacentor and Carios ticks, including nine species of pathogenetic bacteria and potentially new species within the genus Borrelia. We also used these data to explore the evolutionary relationship between ticks and their associated bacteria, revealing a pattern of long-term co-divergence relationship between ticks and Rickettsia and Coxiella bacteria.

Conclusions

In sum, our study provides important new information on the genetic diversity of ticks based on an analysis of mitochondrial DNA as well as on the prevalence of tick-borne pathogens in China. It also sheds new light on the long-term evolutionary and ecological relationships between ticks and their associated bacteria.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05485-3.

Recent Advances in the Immunologic Method Applied to Tick-Borne Diseases in Brazil

Zoonotic-origin infectious diseases are one of the major concerns of human and veterinary health systems. Ticks, as vectors of several zoonotic diseases, are ranked second only to mosquitoes as vectors. Many ticks’ transmitted infections are still endemic in the Americas, Europe, and Africa and represent approximately 17% of their infectious diseases population. Although our scientific capacity to identify and diagnose diseases is increasing, it remains a challenge in the case of tick-borne conditions. For example, in 2017, 160 cases of the Brazilian Spotted Fever (BSF, a tick-borne illness) were confirmed, alarming the notifiable diseases information system. Conversely, Brazilian borreliosis and ehrlichiosis do not require notification. Still, an increasing number of cases in humans and dogs have been reported in southeast and northeastern Brazil. Immunological methods applied to human and dog tick-borne diseases (TBD) show low sensitivity and specificity, cross-reactions, and false IgM positivity. Thus, the diagnosis and management of TBD are hampered by the personal tools and indirect markers used. Therefore, specific and rapid methods urgently need to be developed to diagnose the various types of tick-borne bacterial diseases. This review presents a brief historical perspective on the evolution of serological assays and recent advances in diagnostic tests for TBD (ehrlichiosis, BSF, and borreliosis) in humans and dogs, mainly applied in Brazil. Additionally, this review covers the emerging technologies available in diagnosing TBD, including biosensors, and discusses their potential for future use as gold standards in diagnosing these diseases.

Survey of tick species and molecular detection of selected tick-borne pathogens in Yanbian, China

Ticks and tick-borne diseases pose a significant threat to public health. In this study, we aimed to determine the tick species distribution and pathogens carried by ticks in Yanbian, China. A total of 2673 questing ticks were collected from eight counties and cities in Yanbian and were morphologically identified. The presence of Candidatus Rickettsia tarasevichiae (CRT), spotted fever group Rickettsia (SFGR), severe fever thrombocytopenia syndrome virus (SFTSV), Theileria, and other pathogens was confirmed using polymerase chain reaction (PCR) and real-time quantitative PCR assays, followed by phylogenetic and genotypic analyses. According to the morphological identification, the tick species in Yanbian consisted of Haemaphysalis longicornis, Ixodes persulcatus, Dermacentor silvarum, H. japonica, and H. concinna. In H. longicornis, CRT, SFGR, SFTSV and Theileria orientalis were detected, while CRT, SFGR, and SFTSV were detected in I. persulcatus, H. japonica, and D. silvarum. Only SFTSV was detected in H. concinna. Mixed infection with CRT and SFTSV was observed in I. persulcatus and H. japonica. The gene sequences of all tested pathogens exhibited 95.7%–100% identity with the corresponding sequences deposited in GenBank. Phylogenetic analysis showed that different SFGR and SFTSV genotypes were closely related to the Korean strains. This study is the first to describe the genetic diversity of SFGR Candidatus Rickettsia longicornii in H. longicornis in Yanbian, China, using the ompA, ompB, sca4, and rrs genes. These results provide epidemiological data to support the prevention and control of ticks and tick-borne diseases in the border areas of China, North Korea, and Russia.

Bacterial microbiota analysis demonstrates that ticks can acquire bacteria from habitat and host blood meal

Ticks have a diversity of habitats and host blood meals. Whether and how factors such as tick developmental stages, habitats and host blood meals affect tick bacterial microbiota is poorly elucidated. In the present study, we investigated the bacterial microbiotas of the hard tick Haemaphysalis longicornis, their blood meals and habitats using 16S rRNA gene high-throughput sequencing. The bacterial richness and diversity in ticks varied depending on the tick developmental stage and feeding status. Results showed that fed ticks present a higher bacterial richness suggesting that ticks may acquire bacteria from blood meals. The significant overlap of the bacteria of fed ticks and the host blood also supports this possibility. Another possibility is that blood meals can stimulate the proliferation of certain bacteria. However, most shared bacteria cannot transmit throughout the tick life cycle, as they were not present in tick eggs. The most shared bacteria between ticks and habitats are members of the genera Staphylococcus, Pseudomonas, Enterobacter, Acinetobacter and Stenotrophomonas, suggesting that these environmental bacteria cannot be completely washed away and can be acquired by ticks. The predominant proportion of Coxiella in fed females further demonstrates that this genus is involved in H. longicornis physiology, such as feeding activity and nutritional provision. These findings further reveal that the bacterial composition of ticks is influenced by a variety of factors and will help in subsequent studies of the function of these bacteria.

Protozoan and Rickettsial Pathogens in Ticks Collected from Infested Cattle from Turkey

Diseases caused by tick-transmitted pathogens including bacteria, viruses, and protozoa are of veterinary and medical importance, especially in tropical and subtropical regions including Turkey. Hence, molecular surveillance of tick-borne diseases will improve the understanding of their distribution towards effective control. This study aimed to investigate the presence and perform molecular characterization of Babesia sp., Theileria sp., Anaplasma sp., Ehrlichia sp., and Rickettsia sp. in tick species collected from cattle in five provinces of Turkey. A total of 277 adult ticks (males and females) were collected. After microscopic identification, tick pools were generated according to tick species, host animal, and sampling sites prior to DNA extraction. Molecular identification of the tick species was conducted through PCR assays. Out of 90 DNA pools, 57.8% (52/90) were detected to harbor at least 1 pathogen. The most frequently-detected pathogens were Babesia bovis, with a minimum detection rate of 7.9%, followed by Ehrlichia sp. (7.2%), Theileria annulata (5.8%), Coxiella sp. (3.3%), Anaplasma marginale (2.5%), Rickettsia sp. (2.5%), and B. occultans (0.7%). Rickettsia sp. identified in this study include Candidatus Rickettsia barbariae, R. aeschlimannii, and Rickettsia sp. Chad. All sequences obtained from this study showed 99.05−100% nucleotide identity with those deposited in GenBank (query cover range: 89−100%). This is the first molecular detection of Rickettsia sp. Chad, a variant of Astrakhan fever rickettsia, in Turkey. Results from this survey provide a reference for the distribution of ticks and tick-borne pathogens in cattle and expand the knowledge of tick-borne diseases in Turkey.

miR-2a and miR-279 are functionally associated with cold tolerance in Dermacentor silvarum (Acari: Ixodidae)

Ticks are obligate blood-sucking ectoparasites that can attack mammals, birds, reptiles as well as amphibians. Dermacentor silvarum, an important vector of various pathogenic bacteria, viruses, and protozoans, is widely distributed in China. MicroRNAs (miRNAs) are ~22 nucleotide non-coding small RNA molecules, involved in the regulation of various physiological and cellular processes. Previous studies demonstrated the vital roles of miRNAs during the reproduction and development of ticks, whereas, the regulatory/functional roles of microRNAs during the cold response of ticks remain unexplored. Here, we identified and functionally explored D. silvarum miRNAs involved in cold response to gain further understanding of the molecular regulatory mechanisms underlying cold stress in ticks. The microRNA libraries of D. silvarum were established via high-throughput sequencing after exposure to different cold treatments. A total of 147 miRNAs, including 44 known miRNAs and 103 new miRNAs, were identified. The verification of six highly differentially expressed miRNAs (miR-2a, miR-5305, miR-7, miR-279, miR-993, and novel-3) via RT-qPCR were consistent with the high-throughput sequence results. miR-2a peaked by day 6 and miR-279 expression was lowest by day 3 after cold treatment. The potential target genes of miR-2a and miR-279 were the glycogen phosphorylase (GPase) gene and serine gene, respectively. After injecting D. silvarum ticks with miR-2a and miR-279 antagonists, their respective target genes were up-regulated and vice-versa after injection with the agonists. These results indicated that these two miRNAs and their target genes may be involved in the cold response of D. silvarum ticks.

Biodiversity Indices and Medically Importance of Ticks in North Khorasan Province, Northeast of Iran

Background:

Ticks are considered as the main vectors for the transmission of various pathogens such as relapsing fever and CCHF to humans. This study was investigated the biodiversity indices and medically importance of ticks in North Khorasan Province, Northeast of Iran during 2015–2019.

Methods:

Specimens were captured from infested ruminants including cows, sheep, and goats. Additionally, tick collections also were performed on non-domesticated creatures such as turtles, rodents, and hedgehogs. Specimens were identified using valid identification keys. Species diversity, species richness and evenness indices have been calculated to estimate species biodiversity of ticks.

Results:

A total of 1478 adult ticks were collected. The specimens were from two families: Ixodidae (90.05%) and Argasidae (9.95%), 6 genera and 17 species including: Rhipicephalus sanguineus (55.9%), Rhipicephalus bursa (13.4%), Hyalomma marginatum (9.5%), Hyalomma anatolicum (9.5%), Hyalomma asiaticum (0.2%), Hyalomma aegyptium (0.5%), Hyalomma scupense (1.3%), Hyalomma sp (1.2%), Haemaphysalis sulcata (0.7%), Haemaphysalis erinacea (0.1%), Haemaphysalis inermis (0.1%), Haemaphysalis punctata (0.2%), Haemaphysalis concinna (0.1% Boophilus annulatus (1.2), and Dermacentor marginatus (6.1%) among hard ticks as well as Argas persicus (91.8%) and Argas reflexus (8.2%) amongst soft ticks. Rhipicephalus sanguineus, Rh. Bursa, Hy. marginatum and Hy. anatolicum were known as the most frequent species of hard ticks. Tick’s species richness, Shannon diversity index and Simpson index in this area were S= 17, H’= 1.69, D= 0.294 respectively.

Conclusion:

Based on tick distribution veterinary authority, public health organizations and other officials should act for implementation of disease prevention.

The ecdysteroid receptor regulates salivary gland degeneration through apoptosis in Rhipicephalus haemaphysaloides

Background

It is well established that ecdysteroid hormones play an important role in arthropod development and reproduction, mediated by ecdysteroid receptors. Ticks are obligate hematophagous arthropods and vectors of pathogens. The salivary gland plays an essential role in tick growth and reproduction and in the transmission of pathogens to vertebrate hosts. During tick development, the salivary gland undergoes degeneration triggered by ecdysteroid hormones and activated by apoptosis. However, it is unknown how the ecdysteroid receptor and apoptosis regulate salivary gland degeneration. Here, we report the functional ecdysteroid receptor (a heterodimer of the ecdysone receptor [EcR] and ultraspiracle [USP]) isolated from the salivary gland of the tick Rhipicephalus haemaphysaloides and explore the molecular mechanism of ecdysteroid receptor regulation of salivary gland degeneration.

Methods

The full length of RhEcR and RhUSP open reading frames (ORFs) was obtained from the transcriptome. The RhEcR and RhUSP proteins were expressed in a bacterial heterologous system, Escherichia coli. Polyclonal antibodies were produced against synthetic peptides and were able to recognize recombinant and native proteins. Quantitative real-time PCR and western blot were used to detect the distribution of RhEcR, RhUSP, and RhCaspases in the R. haemaphysaloides organs. A proteomics approach was used to analyze the expression profiles of the ecdysteroid receptors, RhCaspases, and other proteins. To analyze the function of the ecdysteroid receptor, RNA interference (RNAi) was used to silence the genes in adult female ticks. Finally, the interaction of RhEcR and RhUSP was identified by heterologous co-expression assays in HEK293T cells.

Results

We identified the functional ecdysone receptor (RhEcR/RhUSP) of 20-hydroxyecdysone from the salivary gland of the tick R. haemaphysaloides. The RhEcR and RhUSP genes have three and two isoforms, respectively, and belong to a nuclear receptor family but with variable N-terminal A/B domains. The RhEcR gene silencing inhibited blood-feeding, blocked engorgement, and restrained salivary gland degeneration, showing the biological role of the RhEcR gene in ticks. In the ecdysteroid signaling pathway, RhEcR silencing inhibited salivary gland degeneration by suppressing caspase-dependent apoptosis. The heterologous expression in mammalian HEK293T cells showed that RhEcR1 interacts with RhUSP1 and induces caspase-dependent apoptosis.

Conclusions

These data show that RhEcR has an essential role in tick physiology and represents a putative target for the control of ticks and tick-borne diseases.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05052-2.

The Ovarian Development Genes of Bisexual and Parthenogenetic Haemaphysalis longicornis Evaluated by Transcriptomics and Proteomics

The tick Haemaphysalis longicornis has two reproductive groups: a bisexual group (HLBP) and a parthenogenetic group (HLPP). The comparative molecular regulation of ovarian development in these two groups is unexplored. We conducted transcriptome sequencing and quantitative proteomics on the ovaries of HLBP and HLPP, in different feeding stages, to evaluate the molecular function of genes associated with ovarian development. The ovarian tissues of HLBP and HLPP were divided into three feeding stages (early-fed, partially-fed and engorged). A total of 87,233 genes and 2,833 proteins were annotated in the ovary of H. longicornis in the different feeding stages. The differentially expressed genes (DEGs) of functional pathway analysis indicated that Lysosome, MAPK Signaling Pathway, Phagosome, Regulation of Actin Cytoskeleton, Endocytosis, Apoptosis, Insulin Signaling Pathway, Oxidative Phosphorylation, and Sphingolipid Metabolism were most abundant in the ovary of H. longicornis in the different feeding stages. Comparing the DEGs between HLBP and HLPP revealed that the ABC Transporter, PI3K-Akt Signaling Pathway and cAMP Signaling Pathway were the most enriched and suggested that the functions of signal transduction mechanisms may have changed during ovarian development. The functions of the annotated proteome of ovarian tissues were strongly correlated with the transcriptome annotation results, and these were further validated using quantitative polymerase chain reaction (qPCR). In the HLBP, the expression of cathepsin L, secreted proteins and glycosidase proteins was significantly up-regulated during feeding stages. In the HLPP, the lysozyme, yolk proteins, heat shock protein, glutathione S transferase, myosin and ATP synthase proteins were up-regulated during feeding stages. The significant differences of the gene expression between HLBP and HLPP indicated that variations in the genetic background and molecular function might exist in the two groups. These results provide a foundation for understanding the molecular mechanism and exploring the functions of genes in the ovarian development of different reproductive groups of H. longicornis.

Prevalence, Distribution, and Molecular Record of Four Hard Ticks from Livestock in the United Arab Emirates

Simple Summary

Ticks, as blood feeders and vectors of many diseases, can negatively impact livestock and human health, with potential economic impacts on the livestock industry. In this study, we documented the occurrence of four tick species (Hyalomma dromedarii, Hyalomma anatolicum, Rhipicephalus sanguineus, and Amblyomma lepidum) on camels, cows, sheep, and goats from three areas in the United Arab Emirates (UAE). Our findings indicated that H. dromedarii was the most prevalent tick species on camels. The other tick species were present at varying levels on hosts. Some of the tick species collected in this study are potential carriers of tick-borne diseases that are serious and sometimes fatal to humans and animals. Thus, there is a need for more research on ticks and tick-borne diseases in the UAE.

Abstract

Ticks are important arthropod vectors that serve as reservoirs of pathogens. Rapid urbanization and changes in animal breeding practices could be causing a rise in tick burden on animals. Studies on tick distribution on livestock and tick molecular diversity from the United Arab Emirates (UAE) are limited. The aim of this study was to (i) provide molecular and morphological identification of tick species, (ii) compare tick infestation between different hosts, (iii) compare tick infestation in relation to the sex of the host, and (iv) assess the prevalence of tick species on hosts. A total of 5950 ticks were collected from camels (4803 ticks), cows (651 ticks), goats (219 ticks), and sheep (277 ticks). Ticks were identified based on morphological characters at the species level using taxonomic keys. In addition, Polymerase Chain Reaction (PCR) amplification of the cytochrome oxidase subunit 1 (cox1) and 16S rRNA mitochondrial genes was used to identify ticks. Four species were confirmed based on molecular and morphological characterization, namely, Hyalomma dromedarii, Hyalomma anatolicum, Rhipicephalus sanguineus, and Amblyomma lepidum. Hyalomma dromedarii (94.3%) was the most abundant species, followed by H. anatolicum (32.8%). Camels were heavily infested (94%) with ticks as compared to cows (38%), sheep (37%), and goats (14%). Widespread occurrence of these four tick species in the UAE poses a risk of spreading tick-borne pathogens wherever the conditions of infection prevail.

Transcriptome profile of Haemaphysalis longicornis (Acari: Ixodidae) exposed to Cymbopogon citratus essential oil and citronellal suggest a cytotoxic mode of action involving mitochondrial Ca2+ overload and depolarization

Haemaphysalis longicornis is an ixodid tick species of medical and veterinary importance. Investigation into the acaricidal activities of botanicals have increased recently but information about their molecular mechanism of action is scarce. Here, RNA-seq analysis of the ticks exposed to Cymbopogon citratus essential oil and citronellal was performed and the responsive genes were identified. More than 6.39 G clean reads with Q₂₀ ≥ 94.88% were obtained for each H. longicornis sample, with an average GC content of 50.94%. Using the Trinity method, 166,710 unigenes with a mean length of 869 bp and a maximum contig length of 29,156 bp were obtained. The upregulation of genes was concentration-dependent in most of the treated groups. Many genes responsive to C. citratus oil and citronellal were stress-related and they include genes associated with adrenergic signaling/calcium channels, cGMP-PKG signaling, apoptosis, focal adhesion, ECM-receptor interaction, ubiquitin-mediated proteolysis, mTOR signaling pathway, and longevity regulating pathway. The upregulation of genes (CACNAID, ADCY9, TPM1, and MYH6) associated with calcium channels suggests a neurotoxic mode of action, whereas, the upregulation of apoptosis-associated genes (CYC, DRONC, CASP7, CASP9, BCL2L1, bcl-xL, etc.) suggests a cytotoxic mode of action. The metabolism of C. citratus essential oil generates oxidative stress which increases the intra-mitochondrial free Ca²⁺ and triggers the formation of reactive oxygen species (ROS) that culminates to mitochondrial depolarization, ATP depletion, and either necrotic or apoptotic death. The neurotoxic and cytotoxic effects exhibited by the monoterpenes in H. longicornis is vital and could be exploited for the advancement of acaricide development and eco-friendly tick control.