Large-Scale Comparative Analyses of Tick Genomes Elucidate Their Genetic Diversity and Vector Capacities.

Among arthropod vectors, ticks transmit the most diverse human and animal pathogens, leading to an increasing number of new challenges worldwide. Here we sequenced and assembled high-quality genomes of six ixodid tick species and further resequenced 678 tick specimens to understand three key aspects of ticks: genetic diversity, population structure, and pathogen distribution. We explored the genetic basis common to ticks, including heme and hemoglobin digestion, iron metabolism, and reactive oxygen species, and unveiled for the first time that genetic structure and pathogen composition in different tick species are mainly shaped by ecological and geographic factors. We further identified species-specific determinants associated with different host ranges, life cycles, and distributions. The findings of this study are an invaluable resource for research and control of ticks and tick-borne diseases.

Mechanism of the toxic effects of tetracycline on blood meal digestion in Haemaphysalis longicornis.

The extensive utilization of antibiotics in the field of animal husbandry gives rise to various concerns pertaining to the environment and human health. Here, we demonstrate that the administration of tetracycline impedes blood meal digestion in the tick Haemaphysalis longicornis. Tissue sectioning, 16S rRNA high-throughput sequencing, and transcriptome sequencing of the midgut were employed to elucidate the mechanism underlying tetracycline toxicity. The treatment group consisted of engorged female ticks that were subjected to tetracycline microinjections (75 µg per tick), whereas the control group received sterile water injections. On days 2 and 4 following the injections, the tick body weight changes were assessed and the midguts were dissected and processed. Change in tick body weight in tetracycline-treated group was less than in the control group. In tetracycline-treated ticks, midgut epithelial cells were loosely connected and blood meal digestion was impaired compared to the control group. There was no significant change in midgut bacterial diversity after tetracycline treatment. On day 2 following treatment, the relative abundance of Escherichia-Shigella was significantly decreased, whereas the relative abundance of Allorhizobium was significantly increased compared to the control group. On day 4 following treatment, the relative abundance of Escherichia-Shigella, Allorhizobium, Ochrobactrum, and Acidibacter decreased significantly, whereas the relative abundance of Paraburkholderia and Pelomonas increased significantly. Tetracycline treatment also affected midgut gene expression, producing a cumulative effect wherein the differentially expressed genes (DEGs) were mostly down-regulated. KEGG enrichment pathway analysis revealed that on day 2 the up-regulated DEGs were significantly enriched in 21 pathways, including apoptosis and phagosome. Comparatively, the down-regulated DEGs were significantly enriched in 26 pathways, including N-glycan biosynthesis, lysosome, and autophagy. In contrast, on day 4 the up-regulated DEGs were significantly enriched in 10 pathways including aminoacyl-tRNA biosynthesis, ribosome biogenesis, RNA transport, and DNA replication, whereas the down-regulated differential genes were significantly enriched in 11 pathways including lysosome, peroxisome, N-glycan biosynthesis, and fatty acid synthesis. This indicates that tetracycline injection inhibited blood meal digestion by affecting midgut digestive cells, gut flora diversity, and gene expression. These findings could contribute to tick control by inhibiting blood meal digestion.

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.

Seasonal abundance and activity of the tick Dermacentor everestianus (Acari: Ixodidae) in the Tibetan Plateau, China.

Dermacentor everestianus is an important vector for several pathogens endemic in the Qinghai-Tibet Plateau. However, knowledge of its seasonal activity and abundance is limited. Hence, the seasonal dynamics of questing and host-feeding D. everestianus were investigated from March 2014 to February 2016 in Damxung County, north of Lhasa City in Tibet. During the 2-year period, questing ticks were collected weekly from two habitats (grassland and shrubs) by flag-dragging. Host-feeding ticks were removed weekly from sheep and their attachment sites were recorded. Plateau pikas (Ochotona curzoniae) captured by traps were examined for immature ticks from May to September 2014. Results revealed that questing D. everestianus were primarily distributed in grassland, whereas host-feeding adults and nymphs were mainly found on sheep, and larvae usually were on plateau pikas. Dermacentor everestianus can complete one generation per year with population overlap between the larvae and nymphs. Adults were mainly observed from February to April with the major peak occurring in late March. Additionally, unfed adults were detected on sheep from August to next February. Nymphs were found from late May to July and reached their peak in late June. Larvae collected during May and June reached peak numbers in late May.

Ticks (Acari: Ixodoidea) in China: Geographical distribution, host diversity, and specificity.

Ticks are obligate blood-sucking ectoparasites, which not only directly damage through bites but also transmit many pathogens. China has a high diversity of tick species, 125 species have been reported, including 111 hard tick and 14 soft tick species. Many of the ticks are important vectors of pathogens, resulting in zoonoses. The dynamics of ticks are affected by both the host and habitat environment. However, systematic studies on the geographical distribution, host diversity, and specificity of ticks are limited in China. To achieve this goal, the relevant available data were summarized and analyzed in this study. Ticks are distributed in all parts of China and Xinjiang has the most records of ticks. The distribution of ticks in adjacent areas is similar, indicating that the habitat environment affects their distribution. Most ticks are widely distributed, whereas some species are endemic to their distributed regions. Ticks are parasitic on mammals, birds, and reptiles, of which mammals are the main host species. Overall, most ticks parasitize different hosts, only a few ticks have strict host specificity, such as ticks that are specifically parasitic on reptiles and bats. In addition, environmental changes and control efforts also influence the dynamics of ticks. These results can better reveal tick biological traits and are valuable for tick control.

The mitochondrial genome of the ornate sheep tick, Dermacentor marginatus.

The ornate sheep tick, Dermacentor marginatus, is widespread in Europe. Its vector role of various zoonotic pathogens received much attention in these regions. However, the genomic resources of the ticks are limited. In this study, the complete mitochondrial genome of a single female D. marginatus collected in Slovakia was sequenced through the Illumina HiSeq sequencing platform. The mitochondrial genome is 15,067 bp long and contains 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes. The overall G+C content is 21.6%. The gene order is identical to that of Metastriata ticks. The codon usage pattern is similar with that of other tick species. As in other ticks, two truncated tRNA genes were observed. Two control regions were found between tRNA-Leu and tRNA-Cys, tRNA-Ile and rrnS, respectively. The mitochondrial genome contains three noncoding regions, which is similar to that in D. nitens. The noncoding region located between rrnS and tRNA-Val is shorter than that of other Dermacentor species. Phylogenetic analyses indicate that D. marginatus is clustered with other Dermacentor species. These findings are helpful for exploring the systematics and evolution of ticks in the future.

The life cycle and development characteristics of Dermacentor everestianus (Acari: Ixodidae) under field conditions in Qinghai-Tibet Plateau.

The tick Dermacentor everestianus mainly distributed in Tibet, China and Nepal, and can transmit some pathogens causing great damages in Qinghai-Tibet Plateau. This study investigated the life cycle and development characteristics of D. everestianus under field conditions. The average duration of the whole life cycle of D. everestianus was 124.4 days, with the host available in the field plot. Under natural conditions, the mean feeding, preoviposition and oviposition period of female ticks were 6.1, 17.9 and 21.2 days, respectively. The incubation time of eggs was the longest phase in the life cycle of the ticks (26 days on average). Moreover, the weight of engorged females was highly positively correlated with the number of the eggs that were laid (r = 0.81, P < 0.05). The reproductive efficiency index and reproductive fitness index in females were 7.3 and 5.9, respectively. The above findings suggest that the tick D. everestianus have evolved well adaptability to the highland areas.

Endosymbiont CLS-HI plays a role in reproduction and development of Haemaphysalis longicornis.

Coxiella-like endosymbiont (CLS-Hl) is a primary endosymbiont of Haemaphysalis longicornis. CLS-Hl infects tick special tissues and its prevalence is 100% in ovaries and Malpighian tubules. Tetracycline was injected into females, which then fed on rabbits also treated with tetracycline. The densities of CLS-Hl were measured by semi-quantitative PCR. CLS-Hl densities in ovaries and Malpighian tubes of H. longicornis had significant effects on engorged weight, feeding time, number of eggs, oviposition period, and hatching period. These findings suggested that CLS-Hl plays a role in the reproduction and development of H. longicornis.

Characterization of the life cycle of the tick Haemaphysalis tibetensis under field conditions in Qinghai-Tibet plateau.

The tick Haemaphysalis tibetensis Hoogstraal is found uniquely in the Qinghai-Tibet plateau of Tibet and Gansu of China. Not much is known of this tick. Therefore, in this study we investigated the life cycle of H. tibetensis under field conditions from March 2014 to March 2015 in Damxung County, north Lhasa City in Tibet (Autonomous Region in China). The results of the study demonstrated that the tick H. tibetensis requires an average of 177.8 days (range 129-202 days) to complete a life cycle, with rabbits supplied as hosts in the field plot. Under natural lighting and climate conditions, the feeding period of females was an average of 7.7 days, and the pre-oviposition period was 9.4 days, followed by 28.2 days for oviposition. The premolting period of nymphs lasted 52.7 days, which was the longest life cycle phase. The average weight ratio of engorged to unfed females was 58.2. Additionally, there was a highly positive correlation between the weight of engorged and the number of the eggs that were laid (r = 0.83, P < 0.05). The reproductive efficiency index and reproductive fitness index in females were 5.1 and 4.7, respectively.

Curcumin combined with oxaliplatin effectively suppress colorectal carcinoma in vivo through inducing apoptosis.

Studies have shown chemopreventive and/or chemotherapeutic effects of several curcumin-based combinatorial treatments on colorectal cancer cells. However, their in vivo effects remain unclear. This study has demonstrated the therapeutic effect of curcumin and oxaliplatin, alone or in combination, on subcutaneously xenografted LoVo human colorectal cancer cells in immunodeficient (nu/nu) mice in vivo. Combinatorial administration of curcumin and oxaliplatin evidently inhibited the growth of colorectal cancer in nude mice, which was significantly more effective than either agent alone. Curcumin combined with oxaliplatin treatment induced apoptosis, accompanied by ultrastructural changes and cell cycle arrest in S and G2/M phases. Further mechanism analysis indicated that while the number of apoptotic tumor cells and the expression of Bax, caspase-3, and poly (ADP-ribose) polymerase (PARP) increased significantly, the expression of Bcl-2, survivin, HSP70, pro-caspase-3, and pro-PARP were dramatically suppressed in tumor cells after the treatment with combinatorial curcumin and oxaliplatin for 22 days. Taken together, the present study has demonstrated that administration of combined curcumin and oxaliplatin effectively suppressed colorectal carcinoma in vivo through inducing apoptosis and thus may provide an effective treatment for colorectal carcinoma.

[An overview on the physiological and ecological adaptation mechanisms of the overwinter ticks].

The current paper introduces the recent research and development on the cryobiology of ticks, based on their overwinter behavior strategy and biochemical and physiological adaptation mechanisms, and provides detail information on the cold hardiness, biochemical and physiological mechanisms, the relationship between cold hardiness and diapause, which will give theoretical clues for subsequent research on the molecular regulation of cold hardiness of ticks.

Tetracycline inhibits tick host reproduction by modulating bacterial microbiota, gene expression and metabolism levels.

BACKGROUND: Ticks are disease vectors that are a matter of worldwide concern. Antibiotic treatments have been used to explore the interactions between ticks and their symbiotic microorganisms. In addition to altering the host microbial community, antibiotics can have toxic effects on the host. RESULTS: In the tick Haemaphysalis longicornis, engorged females showed reproductive disruption after microinjection of tetracycline. Multi-omics approaches were implemented to unravel the mechanisms of tick reproductive inhibition in this study. There were no significant changes in bacterial density in the whole ticks on Day (D)2 or D4 after tetracycline treatment, whereas the bacterial microbial community was significantly altered, especially on D4. The relative abundances of the bacteria Staphylococcus, Bacillus and Pseudomonas decreased after tetracycline treatment, whereas the relative abundances of Coxiella and Rhodococcus increased. Ovarian transcriptional analysis revealed a cumulative effect of tetracycline treatment, as there was a significant increase in the number of differentially expressed genes with treatment time and a higher number of downregulated genes. The tick physiological pathways including lysosome, extracellular matrix (ECM)-receptor interaction, biosynthesis of ubiquinone and other terpenoids-quinones, insect hormone biosynthesis, and focal adhesion were significantly inhibited after 4 days of tetracycline treatment. Metabolite levels were altered after tetracycline treatment and the differences increased with treatment time. The differential metabolites were involved in a variety of physiological pathways; the downregulated metabolites were significantly enriched in the nicotinate and nicotinamide metabolism, galactose metabolism, and ether lipid metabolism pathways. CONCLUSIONS: These findings indicate that tetracycline inhibits tick reproduction through the regulation of tick bacterial communities, gene expression and metabolic levels. The results may provide new strategies for tick control. © 2023 Society of Chemical Industry.

Curcumin inhibits proliferation and induces apoptosis of human colorectal cancer cells by activating the mitochondria apoptotic pathway.

Curcumin, a natural plant extract from Curcuma longa, is known for its anti-carcinogenic and chemopreventive effects on a variety of experimental cancer models. In this study, we evaluated the effects of curcumin and elucidated its mechanism in human colorectal carcinoma cells. Cell viability assay showed that curcumin significantly inhibited the growth of LoVo cells. Curcumin treatment induced the apoptosis accompanied by ultra-structural changes and release of lactate dehydrogenase in a dose-dependent manner. Moreover, treatment with 0-30 µg/mL curcumin decreased the mitochondrial membrane potential and activated the caspase-3 and caspase-9 in a dose- and time-dependent manner. Nuclear and annexin V/PI staining showed that curcumin induced the apoptosis of LoVo cells. FACS analysis revealed that curcumin could induce the cell cycle arrest of LoVo cells at the S phase. Furthermore, western blotting analysis indicated that curcumin induced the release of cytochrome c, a significant increase of Bax and p53 and a marked reduction of Bcl-2 and survivin in LoVo cells. Taken together, our results suggested that curcumin inhibited the growth of LoVo cells by inducing apoptosis through a mitochondria-mediated pathway.

[Study on functions and mechanism of curcumin in inducing colorectal carcinoma cells LoVo apoptosis].

OBJECTIVE: To discuss the biological function and regulation mechanism of curcumin in promoting human colorectal carcinoma (LoVo) cells apoptosis. METHOD: Conventional in vitro culture in human colorectal carcinoma cells LoVo, When 80%-90% confluence was reached, cells were treated with curcumin at different concentrations (0-20 mg x L(-1)). Curcumin's effect on cell proliferation level was examined by MTT colorimetry. The ultrastructure of curcumin-treated LoVo cells were observed with transmission electron microscope (TEM). The amount of PI-positive LoVo cells after the curcumin treatment were determined by flow cytometry. The cell apoptosis rate was detected by Annexin V-FITC/PI double staining. The mRNA level of Bax, Bcl-2, Caspase-3 and Bcl-xL were tested by means of RT-PCR. RESULT: MTT test indicates curcumin could inhibite the growth and proliferation of LoVo cells in a time- and concentration-dependent manner. TEM examination showed that curcumin can make LoVo cell morphological changes, showing the typical characteristics of apoptotic cells. Flow cytometry instrument analysis showed that curcumin can arrest cell cycle at S phase, and induce apoptosis of LoVo cells. RT-PCR test showed that curcumin can activate the expression of Bax and Caspase-3, inhibit the expression of Bcl-2 and Bcl-xL at the mRNA level. CONCLUSION: Curcumin can significantly inhibit the proliferation and induce the apoptosis of human colorectal carcinoma cells LoVo. Such biological effect may be associated with activating Caspase-3 signal channel by activating Bax expression and inhibiting Bcl-2 and Bcl-xL expression. This study lays an important foundation for further discussing the mechanism of curcumin in inducing human colorectal carcinoma LoVo apoptosis.

Revision of the genus Colasia Koch, 1965 (= Belousovia Medvedev, 2007, syn. nov.) (Coleoptera, Tenebrionidae, Blaptini).

The relationship between the genera Colasia Koch, 1965 and Belousovia Medvedev, 2007 within the tribe Blaptini is discussed, and a new synonymy is proposed: Belousovia Medvedev, 2007, syn. nov. of Colasia Koch, 1965. As a result, three new combinations are established: Colasiahelenae (Medvedev, 2007), comb. nov., C.kabakiintermedia (Medvedev, 2007), comb. nov., and C.kabakikabaki (Medvedev, 2007), comb. nov.Colasiaakisoides Koch, 1965 is redescribed, and a lectotype is designated. Three new species of the genus Colasia are described and illustrated from China: C.bijicasp. nov. (Guizhou), C.medvedevisp. nov. (Yunnan), and C.pilosasp. nov. (Yunnan). A distribution map and a key to species of the revised genus Colasia are presented.

Contribution to the knowledge of the genus Solskyia Solsky, 1881 (Coleoptera, Tenebrionidae, Akidini) from China.

Two new species of the genus Solskyia, S.infossata sp. nov. and S.lhozhaga sp. nov., are described and illustrated from Xizang, China. Solskyialhasana is redescribed and figured based on a male, and new material of S.caporiaccoi and S.parvicollis from China is documented. The ecology and biology of adults and larvae is briefly introduced. Furthermore, photographs of habitat, and a key to Chinese species are presented.

Growth dynamics and tissue localization of a Coxiella-like endosymbiont in the tick Haemaphysalis longicornis.

A Coxiella-like endosymbiont (Coxiella-LE hereinafter) stably infects and influences Haemaphysalis longicornis development, indicating a mutualistic relationship of Coxiella-LE and ticks. To further elucidate the patterns of growth dynamics and tissue localization of Coxiella-LE in H. longicornis, 16S rRNA high-throughput sequencing, quantitative PCR (qPCR), and fluorescence in situ hybridization (FISH) were used in this study. The density of Coxiella-LE varied among different tick life stages, and fed female ticks had the highest density, followed by unfed female and unfed larval ticks. In the four organs that were dissected from fed female ticks, the ovary carried the highest density of Coxiella-LE, which was significantly different from salivary glands, midgut and Malpighian tubules. The high abundance of Coxiella-LE in fed female ticks and in the ovaries of fed female ticks in the bacterial microbiota analyses further confirmed that Coxiella-LE rapidly proliferates in the ovary after blood feeding. The ovaries continued to develop after engorgement and oviposition began on day 5, with a significant decrease in the density of Coxiella-LE in the ovaries occurring on day 7. FISH results indicated that Coxiella-LE is mainly colonized in the cytoplasm of the oocyte and proliferates with oogenesis. Coxiella-LE was expelled from the body with the mature oocyte, ensuring its vertical transmission. In the Malpighian tubules at different days after engorgement, the white flocculent materials were increasing, and the density of Coxiella-LE raised significantly on day 7. Unlike the localization pattern in the ovary, Coxiella-LE was initially distributed in a mass and continually increased during the development of Malpighian tubules until it filled the Malpighian tubules. These findings provide new insights on the growth dynamics and tissue localization of Coxiella-LE in ticks and are useful for further investigation on the interactions of symbiont and ticks .

[Illustrated keys to families and genera of the superfamily Ixodoidea under new taxonomic system].

Since molecular biology techniques were applied in the phylogeny of ticks in the late 20th century, changes have taken place in the nomenclature and taxonomy of ticks. However, the illustrated keys to families and genera of ticks published in China were incompetence and the taxonomic system was out of date. This article presents a manual of illustrated keys to families and genera of the superfamily Ixodoidea based on the taxonomic system proposed by Barker and Murrell (2004), and provides a foundation for morphological identification of ticks.

Evaluation on two types of paramyosin vaccines for the control of Haemaphysalis longicornis infestations in rabbits.

BACKGROUND: Haemaphysalis longicornis is an obligate hematophagous ectoparasite that transmits a variety of pathogens causing life-threatening diseases in humans and animals. Paramyosin (Pmy) is not only an invertebrate-specific myofibrillar protein but also an important immunomodulatory protein. Therefore, it is one of the ideal candidate antigens for vaccines. METHODS: We conducted two vaccine trials to evaluate the protective efficacy of Pmy recombinant protein (rPmy) and peptide vaccine (KLH-LEE). Each rabbit was immunized with three doses of rPmy or KLH-LEE adjuvanted with Freund's complete/incomplete at 500 µg/dose at 2-week intervals before challenge with 40 female H. longicornis/rabbit. PBS plus adjuvant, Trx or KLH was used as control group. The antibodies of rabbits were detected by ELISA. Then, female ticks were fed on the rabbits until detachment. RESULTS: ELISA results showed that both vaccines induced rabbits to produce antibodies. Compared with the Trx group, the engorgement weight, oviposition and hatchability of the rPmy group decreased by 8.87%, 26.83% and 38.86%, respectively. On the other hand, engorgement weight, oviposition and hatchability of female ticks in the KLH-LEE group correspondingly resulted in 27.03%, 53.15% and 38.40% reduction compared with that of the KLH group. Considering the cumulative effect of vaccination on the evaluated parameters, results showed 60.37% efficacy of the rPmy vaccine formulation and 70.86% efficacy in the KLH-LEE group. CONCLUSIONS: Pmy and particularly epitope LEE have potential for further development of an effective candidate vaccine to protect the host against tick infection. GRAPHIC ABSTARCT.

Investigation of three enzymes and their roles in the embryonic development of parthenogenetic Haemaphysalis longicornis.

BACKGROUND: The tick Haemaphysalis longicornis exhibits two separate reproductive populations: bisexual and parthenogenetic, which have diploid and triploid karyotypes, respectively. The parthenogenetic population can undergo engorgement without copulation and produce viable female-only offspring with a longer incubation period than the bisexual population. Three enzymes, cathepsin B, cathepsin D and acid phosphatase, were found to be involved in vitellin degradation during the embryonic development of bisexual H. longicornis. However, the expression and activity profiles of these enzymes during the embryonic development of parthenogenetic ticks remain unknown. In the present study, the transcriptional expression profile, enzyme activity and roles in embryogenesis of the three enzymes during the embryonic development of parthenogenetic H. longicornis were investigated. METHODS: Quantitative real-time polymerase chain reaction (qPCR) and fluorescence detection were used to analyze the dynamic changes in the three enzymes during embryogenesis. The roles of the three enzymes during embryogenesis were also explored using RNA interference (RNAi). RESULTS: The three enzymes were all expressed during embryonic development in parthenogenetic H. longicornis. The expression of cathepsin B was highest on day 15, whereas that of cathepsin D was highest on day 3 and the peak of acid phosphatase expression occurred on day 9. The activity of cathepsin B was highest on day 3 and lowest on day 5, then gradually increased and remained stable. Cathepsin D activity was highest on day 1 and showed a gradually decreasing trend, whereas acid phosphatase showed the opposite trend and reached a peak on day 23. RNA interference experiments in engorged female ticks revealed that there was no significant difference in the number of eggs laid, but the hatching rate of the eggs was significantly decreased. CONCLUSION: The three enzymes all play important roles in embryonic development of H. longicornis, but the expression patterns and changes in the activity of the enzymes in the bisexual and parthenogenetic populations are different. The results will help a better understanding of the similarities and differences underlying embryonic development in the bisexual and parthenogenetic populations and contribute to the future exploration of the development of the parthenogenetic population of H. longicornis.