Development and biological characteristics of Haemaphysalis longicornis (Acari: Ixodidae) under field conditions

Seasonal dynamics of Haemaphysalis tick species as SFTSV vectors in South Korea

Ticks pose a significant public health threat due to their ability to transmit various pathogens, including emerging tick-borne diseases. This study conducted a comprehensive surveillance of Haemaphysalis tick species and their severe fever with thrombocytopenia syndrome virus (SFTSV) infection rates in South Korea throughout the year 2023, from January to December. To ensure accurate and rapid identification of the prevalent Haemaphysalis tick species in South Korea, we designed PCR primer sets targeting the ITS1 gene, specifically distinguishing Haemaphysalis longicornis from Haemaphysalis flava. Among the 10,343 ticks collected from wild animals, H. longicornis constituted the majority, accounting for 65.5% (6,784/10,343 ticks), followed by H. flava at 33.8% (3,491/10,343 ticks), and Ixodes nipponensis at 0.7% (68/10,343 ticks). These identified ticks were then categorized into 811 pools, with 63 pools testing positive for SFTSV. Remarkably, the prevalence of SFTSV-positive H. longicornis ticks peaked during the summer months, aligning with heightened human outdoor activities and, consequently, an increased risk of human exposure. Conversely, it is noteworthy that H. flava exhibited a higher prevalence during the winter season, reaching its peak in January, with an SFTSV minimum infection rate similar to that of H. longicornis. These findings underscore the year-round presence of Haemaphysalis ticks as potential vectors for SFTSV, extending the temporal window for potential human exposure. Consequently, these results emphasize the necessity for active and continuous field surveillance to comprehensively understand and mitigate the public health risks associated with these tick-borne pathogens.

IMPORTANCE

To date, the majority of tick surveillance studies have primarily focused on warmer seasons, which are considered optimal periods for ticks to actively seek hosts and transmit pathogens through blood-feeding activities. Consequently, tick species active during winter have often been overlooked, leading to an underestimation of their significance in transmitting severe fever with thrombocytopenia syndrome virus (SFTSV). In this study, we aimed to examine year-round tick prevalence with SFTSV and illuminate the role of the winter-dominant species, Haemaphysalis flava, in South Korea. Through rigorous identification facilitated by a primer set designed specifically for this purpose, we emphasize that H. flava, a competent vector species, harbors SFTSV in the winter season, thereby acting as an overwintering reservoir for the virus. This phenomenon may contribute to a higher infection rate among ticks in the following year.

Current Progress of Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) Vaccine Development

SFTSV is an emerging tick-borne virus causing hemorrhagic fever with a case fatality rate (CFR) that can reach up to 27%. With endemic infection in East Asia and the recent spread of the vector tick to more than 20 states in the United States, the SFTSV outbreak is a globally growing public health concern. However, there is currently no targeted antiviral therapy or licensed vaccine against SFTSV. Considering the age-dependent SFTS pathogenesis and disease outcome, a sophisticated vaccine development approach is required to safeguard the elderly population from lethal SFTSV infection. Given the recent emergence of SFTSV, the establishment of animal models to study immunogenicity and protection from SFTS symptoms has only occurred recently. The latest research efforts have applied diverse vaccine development approaches-including live-attenuated vaccine, DNA vaccine, whole inactivated virus vaccine, viral vector vaccine, protein subunit vaccine, and mRNA vaccine-in the quest to develop a safe and effective vaccine against SFTSV. This review aims to outline the current progress in SFTSV vaccine development and suggest future directions to enhance the safety and efficacy of these vaccines, ensuring their suitability for clinical application.

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.

Population dynamics of hard ticks (Acari: Ixodidae) and their harboring rates of Severe Fever with Thrombocytopenia Syndrome (SFTS) virus in four landscapes of Gyeonggi Province, South Korea

Population dynamics of hard ticks and their harboring rates of fatal severe fever with thrombocytopenia syndrome (SFTS) were monitored from 2021 to 2022 in Gyeonggi-do, South Korea. Hard ticks were surveyed monthly using CO2-bait traps in four vegetation types, including grassland, grave, mountain trail, and shrub. From the 2-year monitoring, totals of 5,737 and 14,298 hard ticks were collected in 2021 and 2022, respectively, all of which belonged to the genus Haemaphysalis. Of these collected ticks, 97.9 and 98.3% of adults and nymphs were identified as Haemaphysalis longicornis. Generally, density peaks of H. longicornis nymphs and adults were observed from April to May and from June to July, respectively. For Haemaphysalis flava, adults showed density peaks in September, whereas no obvious seasonal patterns were observed for nymphs. The density peak of Haemaphysalis larvae was observed in August and September, followed by a density peak of adults. There was a large variation in the number of hard ticks collected among the four vegetation types, yielding no significant difference among them over the 2-year monitoring. Half of the collected ticks from each vegetation type were pooled into groups by species and developmental stage and subjected to analysis of SFTS virus harboring rates, which yielded no SFTS positive pool detected over the 2-year monitoring.

Severe fever with thrombocytopenia syndrome incidence could be associated with ecotone between forest and cultivated land in rural settings of central China

Severe fever with thrombocytopenia syndrome (SFTS), an emerging tick-borne disease first reported in rural areas of central China, has become a major public health concern in endemic areas. The epidemic dynamic and ecologic factors of SFTS incidence at a village scale remain unclear. Here we analyzed the epidemiological characteristics of SFTS cases in Shangcheng County, the first reported areas of SFTS in China. A retrospective space-time cluster analysis was conducted to identify the dynamics of hotspot areas, and the negative binomial regression model was conducted to examine potential factors contributing to the incidence of SFTS at the village level. A total of 1,219 SFTS cases were reported in Shangcheng County from 2011 to 2020, with a case fatality rate of 12.0%. The median age of patients was 64 years, and 81.7% of patients were over 50 years old. Women accounted for 60.3% of all cases, and the incidence rate was significantly higher than that of men (Pearson χ² test, P<0.001). Five spatial-temporal clusters were identified, and mostly distributed in the central part of the county. Higher risk of SFTS incidence was shown in villages with higher percentage coverages of forest and tea plantation, and higher goat density. In villages where the ratio of cultivated land area to forest land area was between 0.2 and 1.2, the risk of SFTS incidence increased significantly, with an incidence rate ratio of 1.33 (95% CI: 1.04‒1.72, p = 0.024). Our findings indicated that ecotone between forest and cultivated land might be the most important risk settings for exposure and infection with SFTS virus in endemic areas of central China. Precise identification of risk factors and high-risk areas at a suitable scale is conducive to carrying out targeted measures and improving the surveillance of the disease.

DNA Methylation Variation Is a Possible Mechanism in the Response of Haemaphysalis longicornis to Low-Temperature Stress

Ticks are notorious ectoparasites and transmit the greatest variety of pathogens than any other arthropods. Cold tolerance is a key determinant of tick abundance and distribution. While studies have shown that DNA methylation is one of the important epigenetic regulations found across many species and plays a significant role in their response to low-temperature stress, its role in the response of ticks to low-temperature stress remains unexplored. Herein, we explored the DNA methylation profile of the tick, Haemaphysalis longicornis, exposed to low-temperature stress (4 °C) using whole-genome bisulfite sequencing (WGBS). We found that approximately 0.95% and 0.94% of the genomic C sites were methylated in the control and low-temperature groups, respectively. Moreover, the methylation level under the CG context was about 3.86% and 3.85% in the control and low-temperature groups, respectively. In addition, a total of 6087 differentially methylated regions (DMRs) were identified between the low-temperature and control groups, including 3288 hypermethylated and 2799 hypomethylated DMRs. Further, Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of differentially methylated genes revealed that most of the DMGs were significantly enriched in binding and RNA transport pathways. Taken together, this research confirmed, for the first time, the whole genome DNA methylation profile of H. longicornis and provided new insights into the DNA methylation changes relating to low-temperature stress in H. longicornis, as well as provided a foundation for future studies on the epigenetic mechanism underlying the responses of ticks to abiotic stress.

The Distribution, Seasonal Abundance, and Environmental Factors Contributing to the Presence of the Asian Longhorned Tick (Haemaphysalis longicornis, Acari: Ixodidae) in Central Appalachian Virginia

Over the past decade, Haemaphysalis longicornis, the Asian longhorned tick, has undergone a geographic range expansion in the United States, from its historical range in east Asia. This tick has been characterized by its frequent parasitism of livestock, an ability to reproduce through parthenogenesis, and its ability to transmit a variety of vector-borne pathogens to livestock, wildlife, and human hosts in its native geographic range. Thus far in the United States, 17 states have reported H. longicornis populations, including 38 counties in Virginia. These numbers come from presence-absence reports provided to the U.S. Department of Agriculture, but little has been reported about this ticks' seasonality in Virginia or its habitat preferences. Our current study detected H. longicornis populations in seven of the nine surveyed counties in Virginia. Haemaphysalis longicornis were observed in multiple habitat types including mixed hardwood forests and pastures, with abundant H. longicornis populations detected at one particular pasture site in Wythe County. This study also attempted to investigate environmental conditions that may be of importance in predicting tick presence likelihood. While sample size limited the scope of these efforts, habitat type and climatic metrics were found to be important indicators of H. longicornis collection success and abundance for both the nymphal and larval life stages. This current study reports useful surveillance data for monitoring these tick populations as they become established in the western half of Virginia and provides insight into their current distribution and maintenance over a large study region.

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 distribution of Haemaphysalis longicornis (Acari: Ixodidae) and detection of SFTS virus in Gyeongbuk Province, Republic of Korea, 2018

The seasonal distribution of hard ticks was investigated in 2018 in Gyeongbuk Province, Republic of Korea. Ticks were assayed for severe fever with thrombocytopenia syndrome virus (SFTSV). Ticks were collected monthly using CO₂-baited traps from April to November in four habitats (grasslands, grave sites, hiking trails, and mixed forests). Based on morphological and molecular identification, Haemaphysalis longicornis was the most commonly collected species, followed by H. flava and Ixodes nipponensis. Ticks were more commonly collected in grassland habitats, followed by the grave sites, hiking trails, and mixed forests. Peak numbers of nymphs and adults of H. longicornis occurred in May and June, respectively, and Haemaphysalis larvae were collected from August to October. A total of 9/187 (4.8%) pools were positive for SFTSV between June and October in 2018. Phylogenetic analysis of partial fragments of the SFTSV obtained in this study showed that all positive virus samples clustered into genotype B.

Survey of severe fever with thrombocytopenia syndrome virus in wild boar in the Republic of Korea

Severe fever with thrombocytopenia syndrome (SFTS) is caused by Dabie bandavirus that belongs to the genus Bandavirus in the family Phenuiviridae and order Bunyavirales and is transmitted by hard ticks. It has been detected in several tick species, various animals, and humans. The purpose of this study was to detect SFTS virus (SFTSV) antigen and antibody in wild boar in the Republic of Korea (ROK). A total of 768 sera samples were collected from wild boar in the ROK between January and December 2019. Viral RNA was extracted from sera using viral RNA extraction kit, and one-step RT-nested polymerase chain reaction (PCR) was performed to amplify the S segment of the SFTSV. The sequencing data were analyzed using Chromas and aligned using Clustal X. The phylogenetic tree was constructed using the maximum-likelihood method using MEGA7. In addition, wild boar sera were tested for IgG antibodies against SFTSV by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA). Of a total of 768 sera samples, 40 (5.2%) were positive for SFTSV by RT-PCR targeting the S segment. Two hundred twenty-one (28.8%) and 159 (20.7%) of 768 sera samples were seropositive by ELISA and IFA, respectively. Based on both ELISA and IFA tests of the same samples, 110 (14.3%) wild boar sera samples were positive for SFTSV antibodies. Of a total of 40 positive serum samples by RT-PCR, 33 (82.5%) and 7 (17.5%) sera were classified as the genotype B-3 and D, respectively, by sequence analysis,. These results provide useful information that demonstrates the detection of antigen and antibody in wild boar sera samples for every month of a certain year throughout the ROK.

Ticks infesting dogs and cats in North America: Biology, geographic distribution, and pathogen transmission

A diverse array of ixodid and argasid ticks infest dogs and cats in North America, resulting in skin lesions, blood loss, and disease. The ticks most commonly found on pets in this region are hard ticks of the genera Amblyomma, Dermacentor, Ixodes, and Rhipicephalus, as well as the more recently established Haemaphysalis longicornis. Soft tick genera, especially Otobius and Ornithodoros, are also reported from pets in some regions. In this review, we provide a summary of the complex and diverse life histories, distinct morphologies, and questing and feeding behaviors of the more common ticks of dogs and cats in North America with a focus on recent changes in geographic distribution. We also review pathogens of dogs and cats associated with the different tick species, some of which can cause serious, potentially fatal disease, and describe the zoonotic risk posed by ticks of pets. Understanding the natural history of ticks and the maintenance cycles responsible for providing an ongoing source of tick-borne infections is critical to effectively combatting the challenges ticks pose to the health of pets and people.

Haemaphysalis longicornis: the life-cycle on dogs and cattle, with confirmation of its vector status for Theileria orientalis in Australia

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Conditions for the optimal generation interval for the “bush tick”, Haemaphysalis longicornis, in Australia have been determined.

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Stabilates containing infective sporozoites of Theileria orientalis ikeda were produced from ground-up ticks (GUTS) and salivary glands of H.longicornis.

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Sporozoites of Theileria orientalis required around 3–5 days of tick feeding to mature in salivary glands before transmission occurred (like T.parva).

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GUTS and salivary gland stabilates produced detectable infections with T.orientalis in naive calves around 3–4 weeks after inoculation.

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This study confirms the final host status of H.longicornis for T.orientalis in Australia, facilitating research for prophylaxis and vector control.

The intracellular protozoal parasite Theileria orientalis ikeda has rapidly spread across South-eastern Australia since 2006, causing deaths and production losses in cattle. The 3-host “bush tick” Haemaphysalis longicornis (Neumann) appears the principal biological vector in the endemic regions. To generate sufficient numbers of ticks to produce stabilate for infection to confirm vector competency and for acaricide trials, the optimal conditions and stage-specific intervals for the generational life-cycle of H.longicornis was defined on two dogs and two steers. To determine whether H.longicornis was a definitive host for Theileria orientalis, nymphal stages were fed on a steer infected with T.orientalis and moulted adults were permitted to feed for 3 days on an uninfected calf prior to harvest. Subsequent detection of infection after inoculation of four naïve calves with stabilate produced from ground-up adult ticks or dissected salivary glands confirmed H.longicornis as one final (definitive) host for T.orientalis in Australia.

Determining Effects of Winter Weather Conditions on Adult Amblyomma americanum (Acari: Ixodidae) Survival in Connecticut and Maine, USA

The lone star tick (Amblyomma americanum L.) is native to the United States, with its primary range encompassing the Southeast and portions of the Midwest. It is an aggressive ectoparasite that actively seeks out hosts through detection of carbon dioxide and vibrations and can transfer ehrlichiosis-causing bacteria as well as a carbohydrate that causes alpha-gal syndrome (red meat allergy) in humans. It has become of increasing concern as its range has recently expanded into coastal regions of the Northeast. Historically, harsh northeastern winter weather conditions made these areas inhospitable for A. americanum survival, but a warming climate coupled with increased host availability seem to have facilitated their range expansion. We developed a study to observe the effects of weather conditions on adult A. americanum overwintering survival. The study was conducted over three years in Connecticut and Maine. Ground-level conditions were manipulated to determine the effects of differing combinations of natural insulative barriers (leaf litter and snow accumulation) on adult A. americanum survival. We determined that there was a significant difference in survival between the two states, between years in Maine, and between sexes within Connecticut. However, presence or absence of snow and/or leaf litter had no impact on survival. Overall, we found a positive correlation between mean hourly temperature and adult survival in Maine, where temperatures were consistently below freezing. The results of this study can be included in an adaptive, predictive analytic model to accommodate the expected fluctuations and range expansion of A. americanum that will most likely accompany an increase in temperatures throughout the Northeast.

Assessment of potential effects and detection efficacy of a fluorescent marking system on a medically important hard tick, Haemaphysalis longicornis (Acari: Ixodidae)

BACKGROUND

Although Haemaphysalis longicornis (Acari: Ixodidae) is an important disease vector, its small size restricts the tracking methods applicable. Recently, fluorescent marking as a conventional detection method for small arthropods has been improved by combining it with an ultraviolet laser. We examined the application potential of this new fluorescent marking system (FMS) for tracking H. longicornis by evaluating the effect of fluorescent marking on the ticks and detection efficacy.

RESULTS

Under laboratory conditions, fluorescent marking did not significantly affect the survivorship, movement patterns, and CO₂ response of H. longicornis at all three developmental stages. Fluorescent-marked individuals could be detected at distances ranging from 12 to 29 m under dark, increasing with the body size. Finally, in grassland, >90% of fluorescent-marked individuals were retrieved at night regardless of developmental stage. However, the overall detection rate (<42%) was substantially reduced during the day.

CONCLUSIOIN

Our results show that FMS can reliably detect H. longicornis at night. Nevertheless, fluorescent-marked individuals are not as conspicuous under sunlight when they are illuminated with ultraviolet lasers, limiting the use of FMS during the day. Therefore, the development of an alternative tracking method is warranted for an effective detection of ticks during the day. © 2019 Society of Chemical Industry.

Shedding and Transmission Modes of Severe Fever With Thrombocytopenia Syndrome Phlebovirus in a Ferret Model

BACKGROUND

Although human-to-human transmission of severe fever with thrombocytopenia syndrome phlebovirus (SFTSV) via direct contact with body fluids has been reported, the role of specific body fluids from SFTSV-infected hosts has not been investigated in detail.

METHODS

To demonstrate the virus transmission kinetics in SFTSV-infected hosts, we adapted the ferret infection model and evaluated the virus shedding periods, virus titers, and transmission modes from various specimens of infected ferrets.

RESULTS

Large amounts of infectious SFTSV are shed through nasal discharge, saliva, and urine from SFTSV-infected ferrets. Virus could be detected from 2 dpi and persisted until 12 dpi in these specimens, compared with the relatively short virus-shedding period in sera. Further, transmission studies revealed that SFTSV can be transmitted to close direct and indirect contact naïve animals through various mediums, especially through contact with serum and urine. Further, ferrets contacted with human urine specimens from SFTSV-positive patients were successfully infected with SFTSV, suggesting that urine specimens could be a source of SFTSV infection in humans.

CONCLUSIONS

Our results demonstrate that the SFTSV can be shed in various body fluids for more than 12 days and that these specimens could be a source for direct or indirect transmission through close personal contact.

De novo assembly and annotation of Hyalomma dromedarii tick (Acari: Ixodidae) sialotranscriptome with regard to gender differences in gene expression

BACKGROUND

Hard ticks are hematophagous ectoparasites characterized by their long-term feeding. The saliva that they secrete during their blood meal is their crucial weapon against host-defense systems including hemostasis, inflammation and immunity. The anti-hemostatic, anti-inflammatory and immune-modulatory activities carried out by tick saliva molecules warrant their pharmacological investigation. The Hyalomma dromedarii Koch, 1844 tick is a common parasite of camels and probably the best adapted to deserts of all hard ticks. Like other hard ticks, the salivary glands of this tick may provide a rich source of many compounds whose biological activities interact directly with host system pathways. Female H. dromedarii ticks feed longer than males, thereby taking in more blood. To investigate the differences in feeding behavior as reflected in salivary compounds, we performed de novo assembly and annotation of H. dromedarii sialotranscriptome paying particular attention to variations in gender gene expression.

RESULTS

The quality-filtered Illumina sequencing reads deriving from a cDNA library of salivary glands led to the assembly of 15,342 transcripts. We deduced that the secreted proteins included: metalloproteases, glycine-rich proteins, mucins, anticoagulants of the mandanin family and lipocalins, among others. Expression analysis revealed differences in the expression of transcripts between male and female H. dromedarii that might explain the blood-feeding strategies employed by both genders.

CONCLUSIONS

The annotated sialome of H. dromedarii helps understand the interaction of tick-host molecules during blood-feeding and can lead to the discovery of new pharmacologically active proteins of ticks of the genus Hyalomma.

Discovery of Haemaphysalis longicornis (Ixodida: Ixodidae) Parasitizing a Sheep in New Jersey, United States

We report the discovery of large numbers of Haemaphysalis longicornis Neumann (Ixodida: Ixodidae) infesting a sheep in Hunterdon County, New Jersey, United States. All life stages were found on the sheep, which had no history of travel outside the country. H. longicornis is native to East Asia, and there are invasive populations in Australia, New Zealand and several Pacific islands, where this tick is a major livestock pest. It is currently unknown whether the New Jersey collections represent a limited or established population, but because this species could present a significant threat to human and animal health in the United States, vigilance is encouraged.

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.

Biology, ecology and distribution of the tick, Haemaphysalis longicornis Neumann (Acari: Ixodidae) in New Zealand

Haemaphysalis longicornis is the only tick in New Zealand that infests livestock. Throughout its range H. longicornis is exposed to and exhibits tolerance to a wide range of environmental conditions, although it flourishes more in moist, warm-temperate environments. This review examines aspects of the biology, physiology and ecology of H. longicornis that determine its distribution and seasonal activity in New Zealand, based on laboratory and field studies. Examples are also drawn from studies outside New Zealand for comparative purposes, especially in the context of seasonal activity as seen in less temperate latitudes. The tick is able to withstand a wide range of temperature, from its developmental threshold of ∼12°C to nearly 40°C at its lethal limit, but its tolerance of dehydration is less wide, especially in the larva and adult, the former especially being the stage that largely determines suitable biotopes for the tick and its present distributional limits. The importance of H. longicornis to the New Zealand livestock industry has recently increased through the establishment and spread of Theileria orientalis Ikeda among dairy and beef cattle, although the tick has always posed production-limiting problems for cattle, deer and to a lesser extent, sheep. The tick's role as a vector of theileriosis and how aspects of the tick's biology affect the spread and maintenance of this disease are discussed. It is proposed that, of available wildlife hosts, the brown hare with its wide-ranging habits, is an important disseminator of ticks. Currently control of ticks is difficult partly because of their wide host range, overlapping activity periods of stadia, and also because the greater part of their annual cycle is spent on pasture. This means that acaricides alone do not satisfactorily reduce tick populations or provide comprehensive protection to stock, so integrated management combining pasture management with good husbandry and chemical prophylaxis is advocated.

Sexual differences in the sialomes of the zebra tick, Rhipicephalus pulchellus

Ticks rely exclusively on vertebrate blood for their survival. During feeding ticks inject into their hosts a sophisticated salivary potion that overcomes host hemostasis and adverse inflammatory responses. These mediators may also enhance pathogen transmission. Knowledge of the tick salivary protein repertoire may lead to vaccine targets to disrupt feeding and/or parasite transmission as well as to the discovery of novel pharmacological agents. Male saliva may also assist reproduction because males use their mouthparts to lubricate and introduce their spermatophores into the females' genital pore. The analyses of the sialomes of male and female ticks independently allow us to understand the strategy used by each gender to feed successfully. We sequenced cDNA libraries from pools of salivary glands from adult male and female Rhipicephalus pulchellus feeding at different time points, using the Illumina HiSeq protocol. De novo assembly of a total of 241,229,128 paired-end reads lead to extraction of 50,460 coding sequences (CDS), 11,277 of which had more than 75% coverage to known transcripts, or represented novel sequences, and were submitted to GenBank. Additionally, we generated the proteome, from the salivary gland extracts of male and female R. pulchellus, yielding a total of 454 and 2063 proteins respectively which were identified by one or more peptides with at least 95% confidence. The data set is presented as an annotated hyperlinked Excel spreadsheet, describing 121 putative secreted protein families. Female and male specific transcripts were identified.

BIOLOGICAL SIGNIFICANCE

This annotated R. pulchellus database represents a mining field for future experiments involving the resolution of time-dependent transcript expression in this tick species, as well as to define novel vaccine targets and discover novel pharmaceuticals. Gender specific proteins may represent different repertoires of pharmacological reagents to assist feeding by each sex, and in males may represent proteins that assist reproduction similarly to seminal proteins in other animals.

Does Haemaphysalis bispinosa (Acari: Ixodidae) really occur in China?

Haemaphysalis bispinosa Neumann has been considered to exist in China, especially in the southern part of the country. However, H. bispinosa referred to in many Chinese research papers may in fact be H. longicornis, which is widely distributed in most regions of China. In order to clarify the occurrence of H. bispinosa, Haemaphysalis ticks collected from 18 of 23 provinces of China (Hebei, Henan, Hubei, Guangxi, Gansu, Yunnan, Xinjiang, Anhui, Zhejiang, Shannxi, Guizhou, Sichuan, Shanxi, Shandong, Ningxia, Fujian, Qinghai and Jiangxi) were examined based on morphological and molecular characteristics. We found no evidence of H. bispinosa being present in China. Our results indicate that all of the so called "H. bispinosa" ticks reported in China are in fact H. longicornis.

The life cycle and occurrence of Haemaphysalis concinna (Acari: Ixodidae) under field conditions

The life cycle and occurrence of Haemaphysalis concinna were investigated under field conditions from April 2012 to March 2013 in Eerguna National Natural Reserve Area situated on the China-Russia border in Inner Mongolia, China. Under natural conditions, the whole life cycle of H. concinna was allowed to complete in a natural tick habitat. With domestic rabbits supplied as hosts, the seasonal occurrence and behaviors of H. concinna were also observed in the field plot which was chosen in a natural tick habitat from April to October 2012. Results indicated that the durations of the life cycle from unfed adults to the next generation unfed adults of H. concinna ranged from 124 to 186 days (average periods of 153.1 days). The incubation time of eggs ranged from 39 to 57 days (average periods of 41.3 days), which is the longest period among the four developmental stages, followed by the premolt periods for larvae (averaged 37.7 days) and nymphs (averaged 26.0 days). The number of eggs was positively correlated with the weight of engorged females (r=0.8562, p<0.001). Eggs were laid in high amounts in the first week, subsequently, the egg amount declined gradually with small peaks occasionally observed. The female reproductive efficiency index (REI) and reproductive fitness index (RFI) was 6.2 and 4.3, respectively. Observations on the occurrence of H. concinna indicated that, in the confined plot under field conditions, larvae appeared in late May and peaked in early July, and nymphs were active during July and August. Therefore, there was an overlap in the occurrence of larvae and nymphs in both June and July.

Cold hardiness and biochemical response to low temperature of the unfed bush tick Haemaphysalis longicornis (Acari: Ixodidae)

Background

The survival of overwintering ticks, is critical for their subsequent population dynamics in the spring, and consequent transmission of tick-borne diseases. Survival is largely influenced by the severity of the winter temperatures and their degree of cold hardiness at the overwintering stage. The bush tick Haemaphysalis longicornis, is widely distributed in China, and can transmit various pathogens that pose serious medical/veterinary problems. In the present study we investigated the effect of low temperature stress to tick survival, super-cooling point and body content of water, glycerol and total protein.

Methods

After various temperature acclimations, the super-cooling point was measured by Ni/CrNi-thermocouples with a precision temperature recorder. Water content was determined from weight loss of the sample exposed to 60°C for 48 h. Glycerol content was determined using Free Glycerol Reagent as directed by the manufacturer, and total protein was determined using the Bradford assay.

Results

The 50% mortality temperatures for the adults and nymphs were -13.7°C and -15.2°C, respectively; and the discriminating temperatures for the adults and nymphs were -16.0°C and -17.0°C, respectively. The super-cooling points of the adults and nymphs were -19.0°C and -22.7°C, respectively. The water content of adult H. longicornis decreased substantially after acclimation at 0°C for 10 d, whereas the nymphs decreased after acclimation at 0°C for 20 d, and the glycerol and proteins of both nymphs and adults were significantly increased (p < 0.01) when stressed at 0°C for 10 d.

Conclusions

In H. longicornis, low temperature stress can enhance its cold hardiness and trigger appropriate responses, including reducing water content, and increasing glycerol and total protein content.

The life cycle of Haemaphysalis qinghaiensis (Acari: Ixodidae) ticks under laboratory conditions

The developmental stages in the life cycle of Haemaphysalis qinghaiensis were investigated under laboratory conditions. The larval, nymphal and adult ticks were fed on sheep at 25-27 °C, 50 % relative humidity (RH) and exposed to daylight. All free-living stages were maintained in an incubator (28 °C with 90 % RH and a 12-h photoperiod). The whole life cycle of H. qinghaiensis was completed in an average of 176 days (range 118-247 days). The average developmental periods were 34.44 days for egg incubation; 5.83, 4.20 and 33.70 days for larval pre-feeding, feeding and pre-molting; and 3.88, 5.30 and 46.50 days for nymphal pre-feeding, feeding and pre-molting. The average times for pre-feeding, feeding, pre-oviposition and oviposition of female adult ticks were 2.60, 11.40, 8.50, and 19.35 days, respectively. The results confirmed the positive correlation between the weight of the engorged female and the egg mass laid (r = 0.557, P < 0.05). The reproductive efficiency index and reproductive fitness index in females were 5.49 and 4.98, respectively. Engorged nymphs moulting to females (4.53 ± 0.16 mg) were significantly heavier (P < 0.001) than those moulting to males (3.45 ± 0.19 mg). The overall sex ratio of the adult ticks was 1:1.1 (M:F).

Morphological, biological and molecular characteristics of bisexual and parthenogenetic Haemaphysalis longicornis

The reproductive mechanism of Haemaphysalis longicornis is quite different from many other animal species. In this article, several characteristics of parthenogenetic and bisexual populations of H. longicornis were analyzed, including some important micro-structures, synchronized life cycle feature and sequences of mitochondrial 16S rRNA gene. The results suggested even though many observations of the two populations were similar to each other, some important differences also existed. The genital apron of parthenogenetic females was wider than that of bisexual females. Parthenogenetic individuals (except engorged females) were significantly larger in weight than bisexual individuals (p<0.01; unfed nymph p<0.05); the difference of nymphal premoulting, female feeding and preoviposition, and egg incubation periods between the two populations were significant (p<0.01); hatch percentage of parthenogenesis was lower than that of bisexual population (69% and 73%, respectively); parthenogenetic individuals had a slightly longer development cycle than bisexual individuals (134 and 129 days, respectively). Hybridization attempts failed between them. Comparing to the two strains of bisexual H. longicornis, parthenogenetic strain of H. longicornis inserted two nucleotides of thymine, though the genetic distance of 16S rDNA between the bisexual and parthenogenetic populations was 0. In order to clarify the relationships of the two reproductive populations of H. longicornis, the sequences of 16S rDNA of four strains of two other species were also analyzed. The divergence between Hebei and Xinjiang strains of Rhipicephalus sanguineus was 0, and the sequences were totally identical between them. The divergence between the two subspecies of Hyalomma asiaticum was 0.01. The results indicated that the relationship between bisexual and parthenogenetic H. longicornis was certainly closer than that between subspecies, but farther than that between the same reproductive populations of conspecies.

Life cycle of Haemaphysalis doenitzi (Acari: Ixodidae) under laboratory conditions and its phylogeny based on mitochondrial 16S rDNA

The paper investigated the life cycle of the hard tick Haemaphysalis doenitzi under laboratory conditions and its phylogeny based on mitochondrial 16S rDNA. The results revealed that the complete life cycle of H. doenitzi requires a mean duration of 109.6 days ranging from 91 to 137 days and the average prefeeding, feeding and premoulting periods of larvae, nymphs and females and the eggs hatching period are 18.7, 26.9, 38.9, and 25.1 days, respectively. In addition, the weight of engorged females is highly correlated with the number of egg masses laid (r = 0.936, P < 0.001). The female reproductive efficiency index and reproductive fitness index are 13.4 and 12.8, respectively. The mean weight of the engorged nymphs (2.77 mg) moulting to females is much higher than those (1.68 mg) moulting to males, which could be used as an index to predict sexes in this species. The ratio of male to female is 1:1.01. Moreover, multisequence alignments and phylogenetic tree constructed based on the mitochondrial 16S rDNA sequences suggest that H. doenitzi is genetically close to H. longicornis.

Seasonal abundance and activity of the hard tick Haemaphysalis longicornis (Acari: Ixodidae) in North China

Seasonal abundance and activity of all the three post-embryogenic stages of Haemaphysalis longicornis, both feeding and free-living phases, were evaluated over a period of 2 years, from February 2008 to January 2010, in North China. Feeding ticks were removed weekly from head and ears of domestic sheep and the attachment sites of this tick were assessed co-instantaneously; free-living ticks were collected weekly in four habitat types by flag-dragging. The results suggested that H. longicornis mainly resides in shrubs and completes one generation per year with population attrition between stages. Infestation of nymphs was detected from March to September with highest peak between late April and early May; adults were detected from April to September with highest peak between late June and July, and an overwintering male population was found during late September to March; infestation of larvae was observed from June to October and peaked between middle August and early September. Most of this tick (91%) attached to head and ears of hosts. Additionally, we captured rodents from April to September 2008, but only a negligible number of nymphs were detected. This result suggested that rodents are not the principal hosts for this tick in the study area.

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

Biological characteristics of Hyalomma rufipes parasitising on rabbits and sheep were compared under laboratory conditions in Gansu, China. Mature ticks could parasitize both rabbits and sheep, while immature ticks only fed on rabbits successfully. Adults sucked blood on sheep significantly longer than on rabbits (16 and 13 days, respectively). Other adult parasite characteristics fed on the two hosts were similar, including the weight of engorged adult, female daily oviposition, and the weight and amount of the egg mass laid. Those indicated that this tick species showed little host specificity between sheep and rabbits during its adult stage. In total, the life cycle of H. rufipes was completed in an average period of 179 days. The average developmental periods were 59 days for egg incubation, 3 and 21 days for immature tick prefeeding and feeding, 2, 12 and 40 days for adult prefeeding, female preoviposition and oviposition. The longer female fed for engorgement, the shorter preoviposition period of engorged female needed, although when the feeding period was less than 15 days, this relationship was not obvious. The results confirmed the correlation between the weight of the engorged female and the number of eggs laid (r = 0.909). The reproductive efficiency index (REI) and reproductive fitness index (RFI) in females was 10.63 and 7.22, respectively. Engorged nymphs moulting to females were significantly heavier (27.6 ± 0.89 mg) than those moulting to males (22.3 ± 0.52 mg). Males outnumbered females by 1.4:1.