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

Metabolic rate does not scale with body size or activity in some tick species

Respiration in ticks is highly efficient and exceptionally low. Ticks can survive years between bloodmeals by having low activity and respiration to conserve energetic resources. Our objective was to compare metabolic (VCO2) and activity rates across 6 tick species. We predicted that VCO2 would be different among species and scale linearly with activity and body mass. Activity and CO2 production were measured for 32 h in 6 tick species: Dermacentor andersoni, D. variabilis, Haemaphysalis longicornis, Rhipicephalus appendiculatus, R. microplus, and R. sanguineus. Individual ticks were measured for 30 min three times to ensure breathing occurred. Absolute and mass-specific VCO2, total activity, body mass, and ventilation patterns were compared among species. As expected, ticks did not always breathe during the 30-minute measurements, especially R. sanguineus. Ventilation patterns differed among species with R. microplus having primarily cyclic patterns and R. appendiculatus having discontinuous gas exchange. VCO2 did not scale with body mass in most species. Haemaphysalis longicornis and R. sanguineus had the lowest VCO2; however, H. longicornis was the second most active species. Life history, including questing behavior and range expansion, could be contributing to differences between species. For instance, H. longicornis had exceptionally low metabolic rates despite above average activity levels, suggesting an energetic advantage which may underlie recently documented range expansions in North America. Our results demonstrate how ticks utilize energetic resources to maximize longevity. Future research describing questing behavior and distribution modeling may help explain differences in metabolic rates and activity and impacts on life history traits.

First detection of Bandavirus dabieense in ticks collected from migratory birds in the Republic of Korea

The causative agent of severe fever with thrombocytopenia syndrome (SFTS) is Bandavirus dabieense, an emerging tick-borne zoonotic pathogen. Migratory birds have often been suggested as potential carriers of ticks that can transmit Bandavirus dabieense; however, their role remains unclear. The Republic of Korea (ROK) holds an important position as a stopover on the East Asian-Australasian Flyway. The present study aimed to investigate the potential involvement of migratory birds in the transmission of the SFTS virus (SFTSV) in the ROK. A total of 4,497 ticks were collected across various regions, including Heuksando and Daecheongdo, in the ROK, from bird migration seasons in 2022 and 2023. Genetic analysis of the SFTSV was performed for 96 ticks collected from 20 different species of migratory birds. Polymerase chain reaction (PCR) fragments of SFTSV were detected in one Haemaphysalis concinna nymph collected from a Black-faced Bunting (Emberiza spodocephala) and one Ixodes turdus nymph collected from an Olive-backed Pipit (Anthus hodgsoni) on Daecheongdo and Heuksando, respectively, during their northward migration in two spring seasons. This finding suggests that migratory birds can be considered as possible carriers and long-distance dispersers of ticks and associated tick-borne diseases. This study highlights the importance of clarifying the role and impact of migratory birds in the rapid expansion of tick-borne diseases, facilitating enhanced preparedness and the development of mitigation measures against emerging SFTS across and beyond East Asia.

Acaricidal activity of Erigeron acer L. root against Haemaphysalis longicornis and phytochemical profiling by liquid chromatography-tandem mass spectrometry

The present study is focused on evaluating acaricidal activity and chemical compositions of Erigeron acer root, which was identified as a promising candidate among fifteen Mongolian plant extracts tested for acaricidal activity. The acaricidal effect was evaluated against Haemaphysalis longicornis, assessed for toxicity to normal human skin fibroblast, and analyzed for its chemical constituents. The acetone extract of E. acer root showed significant activity against H. longicornis, with a lethal concentration (LC50) of 5.31 mg/mL and low toxicity, evidenced by a cytotoxic concentration (CC50) of 267.00 µg/mL. Using liquid chromatography-tandem mass spectrometry and molecular networking, thirteen natural compounds were identified, including pyrrolidines, alkaloids, fatty acids, and flavonoids, highlighting the efficacy of E. acer root extract as an effective acaricide against H. longicornis and offering insights for developing new tick control solutions.

Comparative Analysis of Bisexual and Parthenogenetic Populations in Haemaphysalis Longicornis

Haemaphysalis longicornis, a three-host tick with a wide host range, is widely distributed in different countries and regions. It stands out among ticks due to its unique feature of having both parthenogenetic and bisexual populations. Despite their morphological resemblance, the characteristics of the parthenogenetic population have been overlooked. In this comprehensive study, we systematically compared the similarities and differences between these two populations. Our investigation revealed that the parthenogenetic H. longicornis, widely distributed in China, was found in ten provinces, surpassing the previously reported distribution. Notably, individuals from the parthenogenetic population exhibited a prolonged blood-feeding duration during the larval and nymph stages compared to their bisexual counterparts. Additionally, the life cycle of the parthenogenetic population was observed to be longer. A flow cytometry analysis indicated a DNA content ratio of approximately 2:3 between the bisexual and parthenogenetic populations. A phylogenetic analysis using whole mitochondrial genome sequences resulted in the separation of the phylogenetic tree into two distinct branches. A molecular analysis unveiled a consistent single T-base deletion at nucleotide 8497 in the parthenogenetic population compared to the bisexual population. Both populations displayed high viral infection capability and significant resistance to ivermectin. Intriguingly, despite these differences, the parthenogenetic population exhibited a similar life cycle to the bisexual population, retaining the ability to transmit pathogens such as Severe fever with thrombocytopenia syndrome virus (SFTSV) and Heartland Virus (HRTV). These findings contribute to a deeper understanding of the distinct characteristics and similarities between different populations of H. longicornis, laying the foundation for future research in this field.

Acquisition of Rickettsia rickettsii (Rickettsiales: Rickettsiaceae) by Haemaphysalis longicornis (Acari: Ixodidae) through co-feeding with infected Dermacentor variabilis (Acari: Ixodidae) in the laboratory

Haemaphysalis longicornis (Neumann) is an invasive ixodid tick originating from eastern Asia which recently has become established in the United States. In its native range, this tick can transmit several pathogens to animals and humans, but little is known about its ability to acquire and transmit pathogens native to the United States. Geographic overlap with ticks such as Dermacentor variabilis (Say), a known vector of Rickettsia rickettsii, makes investigation into the interactions between H. longicornis and D. variabilis of interest to the public health community. Previous studies have shown that H. longicornis can serve as a competent vector of R. rickettsii under laboratory settings, but there is little information on its ability to acquire this pathogen via other biologically relevant routes, such as co-feeding. Here, we assess the ability of H. longicornis nymphs to acquire R. rickettsii through co-feeding with infected D. variabilis adults on a vertebrate animal model under laboratory conditions. The median infection prevalence in engorged H. longicornis nymphs across 8 cohorts was 0% with an interquartile range (IQR) of 4.13%. Following transstadial transmission, the median infection prevalence in flat females was 0.7% (IQR = 2.4%). Our results show that co-feeding transmission occurs at low levels in the laboratory between these 2 species. However, based on the relatively low transmission rates, this may not be a likely mechanism of R. rickettsii introduction to H. longicornis.

Emerging Tick-Borne Dabie bandavirus: Virology, Epidemiology, and Prevention

Severe Fever with Thrombocytopenia Syndrome (SFTS), caused by Dabie bandavirus (SFTSV), is an emerging infectious disease first identified in China. Since its discovery, infections have spread throughout East Asian countries primarily through tick bites but also via transmission between animals and humans. The expanding range of ticks, the primary vectors for SFTSV, combined with migration patterns of tick-carrying birds, sets the stage for the global spread of this virus. SFTSV rapidly evolves due to continuous mutation and reassortment; currently, no approved vaccines or antiviral drugs are available. Thus, the threat this virus poses to global health is unmistakable. This review consolidates the most recent research on SFTSV, including its molecular characteristics, transmission pathways through ticks and other animals, as well as the progress in antiviral drug and vaccine development, encompassing animal models and clinical trials.

Description of a novel Babesia sp. genotype from a naturally infected Eurasian lynx (Lynx lynx) in Anatolia, Turkey, with remarks on its morphology and phylogenetic relation to other piroplasmid species

There are very limited data on Babesia species infecting lynx species worldwide, and almost nothing is known about babesias in the Eurasian lynx, the most widely distributed wild feline species in the Palearctic geography. This study describes a novel Babesia sp. genotype in a free-living Eurasian lynx in Turkey, named tentatively as 'Babesia sp. lynx', and its integrated genetic and morphological features. Phylogenetic analyses of piroplasmids with the novel Babesia sp. genotype in the current study indicated that this genotype falls into the 'carnivore clade A' of Babesia sensu stricto (true babesias), at the level of different genes (mainly 18S rRNA, ITS1, ITS2, and cyt b) and is monophyletic with the Babesia sp. Ankara genotype, previously observed in Turkey. Additionally, the constructed phylogenetic trees showed that the Babesia sp. lynx genotype infecting the Eurasian lynx is closely related to certain domestic and wild carnivore babesias, mainly Babesia rossi, Babesia presentii, and Babesia pisicii, at the level of different genes. This study also genetically barcoded the lynx infected with the Babesia sp. lynx and Haemaphysalis erinacei, and specimens collected from the animal revealed significant genetic variations between the sample Ha. erinacei and Babesia sp. Ankara-related Ha. erinacei that persists with sympatric populations in Central Anatolia. The lynx infected with the Babesia sp. lynx genotype was also found to be coinfected with Hepatozoon felis, an adeleorinid tick-borne protozoan parasite infecting wild and domestic felids, confirming for the first time its presence in a lynx species. Therefore, this study is the first to describe a potential novel Babesia sp. using its both morphological and phylogenetic characteristics in a lynx species. Adding the Babesia sp. lynx genotype to the phylogeny of feline piroplasmids significantly expands our knowledge of feline babesias in the Palearctic geography and their putative coevolution with their vertebrate hosts.

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.

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.

Association of the invasive Haemaphysalis longicornis tick with vertebrate hosts, other native tick vectors, and tick-borne pathogens in New York City, USA

Haemaphysalis longicornis, the Asian longhorned tick, is an invasive ixodid tick that has rapidly spread across the northeastern and southeastern regions of the United States since first reported in 2017. The emergence of H. longicornis presents a potential threat for livestock, wildlife, and human health as the host associations and vector potential of this invasive pest in the United States are poorly understood. Previous field data from the United States has shown that H. longicornis was not associated with natural populations of small mammals or birds, but they show a preference for medium sized mammals in laboratory experiments. Therefore, medium and large sized mammals were sampled on Staten Island, New York, United States, to determine H. longicornis host associations and vector potential for a range of human and veterinary pathogens. A total of 97 hosts were sampled and five species of tick (Amblyomma americanum, Dermacentor variabilis, H. longicornis, Ixodes scapularis, Ixodes cookei) were found feeding concurrently on these hosts. Haemaphysalis longicornis was found in the highest proportions compared with other native tick species on raccoons (55.4%), Virginia opossums (28.9%), and white-tailed deer (11.5%). Tissue, blood, and engorged larvae were tested for 17 different pathogens using a nanoscale PCR platform. Infection with five pathogens (Borrelia burgdorferi, Anaplasma phagocytophilum, Rickettsia spp., Mycoplasma haemocanis, and Bartonella spp.) was detected in host samples, but no pathogens were found in any larval samples. These results suggest that although large and medium sized mammals feed large numbers of H. longicornis ticks in the environment, there is presently a low potential for H. longicornis to acquire pathogens from these wildlife hosts.

Comparison of Habitat Suitability Models for Haemaphysalis longicornis Neumann in North America to Determine Its Potential Geographic Range

Haemaphysalis longicornis Neumann, 1901 is a vector of many pathogens of public and veterinary health importance in its native range in East Asia and introduced range in Oceania. In North America, this tick was first detected in New Jersey in 2017. Currently, this tick has been reported from 15 states of the United States. In this study, we modeled the habitat suitability of H. longicornis using the MaxEnt modeling approach. We separated occurrence records from the published literature from four different geographical regions in the world and developed MaxEnt models using relevant environmental variables to describe the potential habitat suitability of this tick in North America. The predictive accuracy of the models was assessed using the U.S. county locations where this tick species has been reported. Our best model predicted that the most suitable North American areas for geographic expansion of H. longicornis are from Arkansas–South Carolina to the south of Quebec–Nova Scotia in the east, and from California to the coast of British Columbia in the west. Enhanced surveillance and further investigation are required to gain a better understanding of the role that this tick might play in the transmission of diseases to humans and animals in North America.

A metagenomic examination of the pathobiome of the invasive tick species, Haemaphysalis longicornis, collected from a New York City borough, USA

Haemaphysalis longicornis, the Asian longhorned tick, is an invasive tick species that has spread rapidly across the northeastern and southeastern regions of the United States in recent years. This invasive pest species, known to transmit several tick-borne pathogens in its native range, is a potential threat to wildlife, livestock, domestic animals, and humans. Questing larval (n = 25), nymph (n = 10), and adult (n = 123), along with host-derived adult (n = 25) H. longicornis ticks were collected from various locations on Staten Island, NY. The pathobiome of each specimen was examined using two different high throughput sequencing approaches, virus enrichment and shotgun metagenomics. An average of 45,828,061 total reads per sample were recovered from the virus enriched samples and an average of 11,381,144 total reads per sample were obtained using shotgun metagenomics. Aside from endogenous viral sequences, no viruses were identified through either approach. Through shotgun metagenomics, Coxiella-like bacteria, Legionella, Sphingomonas, and other bacterial species were recovered. The Coxiella-like agent was ubiquitous and present at high abundances in all samples, suggesting it may be an endosymbiont. The other bacterial agents are not known to be transmitted by ticks. From these analyses, H. longicornis do not appear to host any endemic human tick-borne pathogens in the New York City region.

Newly identified viral genomes in pangolins with fatal disease

Epizootic pathogens pose a major threat to many wildlife species, particularly in the context of rapidly changing environments. Pangolins (order Pholidota) are highly threatened mammals, in large part due to the trade in illegal wildlife. During July to August 2018 four sick wild pangolins (three Manis javanica and one Manis pentadactyla) exhibiting a variety of clinical symptoms were rescued by the Jinhua Wildlife Protection Station in Zhejiang province, China. Although three of these animals died, fortunately one recovered after 2 weeks of symptomatic treatment. Using meta-transcriptomics combined with reverse transcription polymerase chain reaction (RT-PCR), we identified two novel RNA viruses in two of the dead pangolins. Genomic analysis revealed that these viruses were most closely related to pestiviruses and coltiviruses, although still highly genetically distinct, with more than 48 and 25 per cent sequence divergence at the amino acid level, respectively. We named these Dongyang pangolin virus (DYPV) and Lishui pangolin virus (LSPV) based on the sampling site and hosts. Although coltiviruses (LSPV) are known to be transmitted by ticks, we found no evidence of LSPV in ticks sampled close to where the pangolins were collected. In addition, although DYPV was present in nymph ticks (Amblyomma javanense) collected from a diseased pangolin, they were not found in the local tick population. Epidemiological investigation revealed that both novel viruses might have been imported following the illegal international trade of pangolins. Hence, these data indicate that illegal wildlife trafficking not only threatens the status of pangolin populations, but may also spread epizootic pathogens.

Molecular Characterization of Haemaphysalis Species and a Molecular Genetic Key for the Identification of Haemaphysalis of North America

Haemaphysalis longicornis (Acari: Ixodidae), the Asian longhorned tick, is native to East Asia, but has become established in Australia and New Zealand, and more recently in the United States. In North America, there are other native Haemaphysalis species that share similar morphological characteristics and can be difficult to identify if the specimen is damaged. The goal of this study was to develop a cost-effective and rapid molecular diagnostic assay to differentiate between exotic and native Haemaphysalis species to aid in ongoing surveillance of H. longicornis within the United States and help prevent misidentification. We demonstrated that restriction fragment length polymorphisms (RFLPs) targeting the 16S ribosomal RNA and the cytochrome c oxidase subunit I (COI) can be used to differentiate H. longicornis from the other Haemaphysalis species found in North America. Furthermore, we show that this RFLP assay can be applied to Haemaphysalis species endemic to other regions of the world for the rapid identification of damaged specimens. The work presented in this study can serve as the foundation for region specific PCR-RFLP keys for Haemaphysalis and other tick species and can be further applied to other morphometrically challenging taxa.

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.

Theileria orientalis Ikeda Genotype in Cattle, Virginia, USA

Theileria orientalis Ikeda genotype is a parasite that causes a disease in cattle that results in major economic issues in Asia, New Zealand, and Australia. The parasite is transmitted by Haemaphysalis longicornis ticks, which have recently been reported in numerous states throughout the eastern United States. Concurrently, cattle in Virginia showed clinical signs consistent with a hemoprotozoan infection. We used amplicons specific for the major piroplasm surface protein and small subunit rDNA of piroplasms to test blood samples from the cattle by PCR. Bidirectional Sanger sequencing showed sequences with 100% identity with T. orientalis Ikeda genotype 2 sequences. We detected the parasite in 3 unrelated herds and from various animals sampled at 2 time points. Although other benign T. orientalis genotypes are endemic to the United States, detection of T. orientalis Ikeda genotype might represent a risk for the cattle industry in Virginia.

The Complete Mitochondrial Genome and Expression Profile of Mitochondrial Protein-Coding Genes in the Bisexual and Parthenogenetic Haemaphysalis longicornis

The tick Haemaphysalis longicornis is widely distributed in eastern Asia, New Zealand and Australia, and is well-known as a vector of multiple zoonotic pathogens. This species exhibits two reproductive strategies, bisexual and obligate parthenogenetic reproduction. Hence, in the current study, the complete mitochondrial genomes of the bisexual and parthenogenetic populations were assembled and analyzed, and the expression of the mitochondrial protein-coding genes was evaluated and compared between the two reproductive populations. The results indicated that the length of the mitochondrial genomes of the two reproductive populations is 14,694 and 14,693 bp in the bisexual and parthenogenetic populations, respectively. The AT content in the mitochondrial genome of the bisexual and obligate parthenogenetic population reached 77.22 and 77.34%, respectively. The phylogenetic tree was constructed combining 13 protein-coding genes, which showed that the genetic distance between the bisexual and parthenogenetic populations was less than that between the subspecies. The expression of the mitochondrial protein-coding genes was quantitatively analyzed at different feeding status for the bisexual and parthenogenetic populations, and the results showed significant differences in the expression patterns of these genes, suggesting that they might trigger specific energy utilization mechanisms due to their different reproductive strategies and environmental pressures.

Mitochondrial Gene Heterogeneity and Population Genetics of Haemaphysalis longicornis (Acari: Ixodidae) in China

INTRODUCTION

Haemaphysalis longicornis is an important ectoparasite of domestic and wild animals that can transmit many pathogens including viruses, fungi, bacteria and protozoa.

MATERIALS AND METHODS

In this study, we examined genetic variation and population genetics in three mitochondrial (mt) genes [cox1 (cytochrome c subunit 1), rrnL (large subunit ribosomal RNA) and nad5 (NADH dehydrogenase 5)] among four H. longicornis populations from China.

RESULTS

The sizes of the partial sequences of cox1, rrnL and nad5 were 776 bp, 409 bp, 510 bp, respectively. Among the obtained sequences, we identified 22 haplotypes for cox1, 2 haplotypes for rrnL and 17 haplotypes for nad5. Low gene flow and significant genetic differentiation (66.2%) were detected among H. longicornis populations. There was no rapid expansion event in the demographic history of four H. longicornis populations in China. In addition, phylogenetic analyses confirmed that all the Haemaphysalis isolates were H. longicornis which were segregated into two major clades.

CONCLUSION

The mt DNA genes provide a potential novel genetic marker for molecular epidemiology of H. longicornis and assist in the control of tick and tick-borne diseases in humans and animals.

Distribution, Host-Seeking Phenology, and Host and Habitat Associations of Haemaphysalis longicornis Ticks, Staten Island, New York, USA

Haemaphysalis longicornis, an invasive Ixodid tick, was recently reported in the eastern United States. The emergence of these ticks represents a potential threat for livestock, wildlife, and human health. We describe the distribution, host-seeking phenology, and host and habitat associations of these ticks on Staten Island, New York, a borough of New York City.

Annotated List of the Hard Ticks (Acari: Ixodida: Ixodidae) of New Jersey

Standardized tick surveillance requires an understanding of which species may be present. After a thorough review of the scientific literature, as well as government documents, and careful evaluation of existing accessioned tick collections (vouchers) in museums and other repositories, we have determined that the verifiable hard tick fauna of New Jersey (NJ) currently comprises 11 species. Nine are indigenous to North America and two are invasive, including the recently identified Asian longhorned tick, Haemaphysalis longicornis (Neumann, 1901). For each of the 11 species, we summarize NJ collection details and review their known public health and veterinary importance and available information on seasonality. Separately considered are seven additional species that may be present in the state or become established in the future but whose presence is not currently confirmed with NJ vouchers. We compare our list of hard ticks in NJ with those from neighboring states (Connecticut, New York, Pennsylvania, Delaware, and Maryland), discuss the importance of vouchers in tick research and surveillance, and examine the likelihood and public health consequences of additional hard tick species becoming established in NJ.

A countrywide molecular survey leads to a seminal identification of the invasive cattle tick Rhipicephalus (Boophilus) microplus in Cameroon, a decade after it was reported in Cote d'Ivoire

The cattle tick Rhipicephalus microplus is the most important arthropod vector of livestock diseases globally. Since its introduction in West Africa a decade ago, it has been reported in Ivory Coast, Benin, Togo, Mali, Burkina Faso and Nigeria with potentially far-reaching adverse impacts on the livestock sector in the region. Cameroon is located on a major route for transboundary cattle trade between Central and West Africa and it is therefore at risk from R. microplus invasion. This study investigated the occurrence of R. microplus in Cameroon, the genetic polymorphism of the tick and population structure of isolates from different regions of the country to provide data that underpin the design of future vector control programs.

A cross-sectional survey was conducted in which ticks were collected from cattle at 54 sites across the five Agroecological zones (AEZs) within Cameroon. Tick identity (sex and species) was assigned using taxonomic keys. Species identity was confirmed through amplification and sequencing of the mitochondrial COI and 16S rRNA genes. A total of 7091 ticks were collected out of which 1112 (15.6%) were morphologically identified as R. microplus. The presence of R. microplus was confirmed in 4 out of 5 agroecological zones. Only two haplotypes were identified by both COI and 16S rRNA genes, indicating a very low divergence in the genetic structure of the R. microplus population in Cameroon. 16S rRNA sequence analysis revealed a new haplotype specific to Cameroon. Phylogenetic trees revealed that all isolates of R. microplus from Cameroon were grouped into the previously described Africa/Americas clade. Application of a niche modelling algorithm to R. microplus distribution in Cameroon predicted that suitable habitat for the tick extended into southern Nigeria.

This study demonstrated for the first time the presence of R. microplus in Cameroon. Genetic diversity tests indicate that the tick has not evolved significantly since the initial introduction to West Africa. We suggest further longitudinal studies to better define the spatial and temporal expansion of the range of the tick and the drivers of this spread.

High genetic diversity in hard ticks from a China-Myanmar border county

Background

Many tick species have great morphological similarity and are thus grouped into species complexes. Molecular methods are therefore useful in the classification and identification of ticks. However, little is known about the genetic diversity of hard ticks in China, especially at the subspecies level. Tengchong is one of the epidemic foci of tick-borne diseases in China, but the tick species inhabiting the local area are still unknown.

Methods

Eighteen villages in Tengchong County, China, were selected for sampling carried out from September to October 2014. Infesting hard ticks were removed from the body surface of domestic animals and questing ticks were collected from grazing fields. After morphological identification, molecular characteristics of each tick species were analyzed based on both 16S rRNA and cytochrome c oxidase subunit 1 (cox1) gene fragments.

Results

Six tick species were identified based on morphology: Rhipicephalus microplus, R. haemaphysaloides, Ixodes ovatus, Haemaphysalis longicornis, H. shimoga and H. kitaokai. Phylogenetic analysis using the cox1 gene revealed that R. microplus ticks from the present study belong to clade C. For tick samples of both R. haemaphysaloides and I. ovatus, three phylogenetic groups were recognized, and the intergroup genetic distances exceeded the usual tick species boundaries. Haemaphysalis longicornis ticks were clustered into two separate clades based on the cox1 gene. For ticks from both H. shimoga and H. kitaokai, two phylogenetic groups were recognized based on the phylogenetic analysis of the 16S rRNA gene, and the intergroup genetic distances also exceeded the known boundaries for closely related tick species.

Conclusions

According to molecular analyses, new species or subspecies closely related to R. haemaphysaloides, I. ovatus, H. shimoga and H. kitaokai probably exist in the China-Myanmar border Tengchong County, or these ticks form species complexes with highly divergent mitochondrial lineages. Morphological comparisons are warranted to further confirm the taxonomic status of these tick species.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3048-5) contains supplementary material, which is available to authorized users.

Life cycle of Spinose ear tick, Otobius megnini (Acari: Argasidae) infesting the race horses in Nuwara Eliya, Sri Lanka

Otobius megnini infests mainly domesticated and wild animals and occasionally humans. It has been identified as an agent of human and horse otoacariasis in Sri Lanka. The number of nymphal stages in the life cycle of O. megnini varies from one to three in different geographic regions. The present study determined the life cycle of O. megnini infesting the racehorses in Nuwara Eliya. A tick colony was initiated from fully engorged nymphs collected from horses and maintained at 10°C, 22°C and 28°C. Immature stages were reared on New Zealand rabbits. Only the larvae weighing more than 0.9mg (84.9%) moulted to nymphs with a pre-moulting period of 5.6(±1.7) days. None of the larvae maintained at 10±1°C moulted. Larval survival was significantly higher at 28±1°C (44.2±4.3days) than at 22±1°C (35.6±9days). At 28±1°C, majority of nymphs (95.6%) weighing over 10mg moulted into adults within 12.5(±3.1) days. Nymphs kept at 10±1°C underwent diapause for 81.1(±72.0) days. Larger females (>13mg; 93.0%) laid eggs for of 44.6(±17.8) days with a mean pre-oviposition period of 10.3(±5.1) days. Females survived longer (369.8±128.3days) than males (210.4±54.1days; Student's t-test; t=5.9, p=0.001). Some females laid eggs without mating. Otobius megnini successfully completed the life cycle within 123days and has only one nymphal instar similar to the Neotropical population. Currently, O. megnini infestation is a serious problem to horses in the Nuwara Eliya racecourse and may pose a risk of spreading to dairy farms close by owing to its dynamic nature of the life cycle.

New molecular data shed light on the global phylogeny and species limits of the Rhipicephalus sanguineus complex

The Rhipicephalus sanguineus complex is a group of closely related tick species distributed all around the world. In this study, using mitochondrial 16S ribosomal DNA, new specimens of R sanguineus sensu lato from Turkey and Rhipicephalus camicasi from Kenya, were evaluated together with available sequences of this complex in GenBank. Our objectives were to delimit the complex, re-evaluate its global phylogeny and develop a reconstruction of its biogeographic history. Given Turkey's geographical location and its neighboring status within Africa, Asia and Europe, molecular information of R. sanguineus s.l. species from this region could have important implications both on a regional and global scale. Phylogenetic trees obtained with three methods (Bayesian, Maximum Likelihood and Maximum Parsimony) were highly similar and consensus trees gave the same branching patterns and similar node support values. A total of four different clades with up to 9 Operational Taxonomic Units formed strong monophyletic groups. Biogeographic reconstructions demonstrated the importance of populations in Middle East (Turkey) in the spread of the group from Europe to Africa and Asia. Data supported previous conclusions on the existence of two species of R. sanguineus s.l. in South America and the strong molecular similarity between R. camicasi and the so-called tropical lineage of R. sanguineus s.l. These results point to the need of a re-evaluation of most specimens designated as R. sanguineus s.l. in East Europe, Middle East, Africa and Asia after an adequate re-description of this taxon.

Identification of piroplasm infection in questing ticks by RLB: a broad range extension of tick-borne piroplasm in China?

Sensitive and specific diagnostic method for rapid and simultaneous detection and discrimination of the different species is needed for an effective control of piroplasmosis. Here, a reverse line blot (RLB) assay was developed for piroplasm detection. A general pair of primer based on 18S ribosomal RNA (rRNA) gene was used to amplify V4 region of 18S rRNA gene. General and specific probes for 13 piroplasm species were cited from previous publications or designed according to the alignment of 18S rRNA gene sequences. For sensitivity test of RLB assay, serially diluted plasmids of the different species were used to access the sensitivity of the RLB. Four hundred and fifty tick samples collected from grass from different provinces of China were then detected. The result indicated that the RLB assay is highly specific and sensitive, detecting up to 10(2) copies/μl of recombinant plasmid DNA. Multiple piroplasms were detected as single or mixed infection from tick species. Eight piroplasm species, most of which were Theileria annulata (33/450, 7.3 %) or Babesia sp. Xinjiang (30/450, 6.7 %), were found to infect with 89 tick samples in four tick species; no infections with Babesia major, Babesia ovata, Babesia bigemina, Theileria sergenti, or Theileria equi were detected. The piroplasms species-specific RLB assay may have potential clinical application in the simultaneous detection and differentiation of Babesia and Theileria species.

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.

Purification of vitellin and dynamics of vitellogenesis in the parthenogenetic tick Haemaphysalis longicornis (Acari: Ixodidae)

Vitellin (Vt) was purified from eggs of parthenogenetic bush tick Haemaphysalis longicornis by gel filtration and ion exchange chromatography. Our results revealed that only one single Vt existed in parthenogenetic bush tick, and the purified Vt was proved to be a hemoglycolipoprotein consisting of nine polypeptides with molecular weights of 203, 147, 126, 82, 74, 70, 61, 47 and 31 kDa, respectively. Polyclonal antibody and monoclonal antibody against Vt were produced using the purified Vt. The change in vitellogenin (Vg) and Vt levels over time of the parthenogenetic H. longicornis was established, and the Vg content in haemolymph and Vt in ovary at different feeding or engorgement statuses was also determined using a double antibody sandwich enzyme-linked immunosorbent assay. The Vg level in haemolymph was distinctly increased on the day of engorgement (1.785 mg/mL) and continued to increase until 2nd day post-engorgement (5.611 mg/mL). There was a slight decrease in Vg level after 4 days of engorgement, and a second peak was observed on day 2 post-oviposition (10.774 mg/mL). Subsequently, Vg content continuously decreased and reached a low level on the 10th day post-oviposition. The Vt content in ovary continuously increased once the female reached its critical weight (0.024 mg per female), and reached the maximum level on day 2 post-oviposition (1.942 mg per female). Afterwards, Vt content rapidly decreased.

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.

Dermacentor everestianus Hirst, 1926 (Acari: Ixodidae): phylogenetic status inferred from molecular characteristics

Dermacentor everestianus Hirst, 1926, is only reported in Northwestern China and Nepal. Few researches about this species have been involved, especially for molecular characteristics. The taxonomy studies of D.everestianus are mainly based on morphological features, and its taxonomic status is an ongoing controversy. To clarify the molecular characteristics and phylogenetic status of D.everestianus and other related species, the sequences of mitochondrial 16S ribosomal DNA (rDNA) and cox1 fragments were analyzed in the present study. Analysis of 16S rDNA and cox1 sequences showed 99.3-100% identity within D.everestianus individuals, with the genetic divergence among them was 0-0.0086. The interspecific distance of 16S rDNA and cox1 between D.everestianus and some other Palaearctic species including D. silvarum, D. nuttalli, and D. marginatus was much smaller than that between D.everestianus and Nearctic Dermacentor ticks (D.albipictus, D.nitens, and D.variabilis). Such relationships of these ticks were also verified in the phylogenetic analysis. Two major clades were recovered within Dermacentor spp. with more than 90% bootstrap support in the phylogenetic trees. D.everestianus together with D.silvarum, D.nuttalli, and D.marginatus were included in the clade I (Eurasia lineage). Other analyzed tick species including D.variabilis, D.nitens, and D.albipictus formed clade II, which are distributed in Nearctic realm. These indicated that the genus Dermacentor was at least composed of two lineages. Thus, further researches including additionally molecular markers on all Dermacentor species globally should be taken to precisely resolve relationships within Dermacentor.

Multiple lines of evidence on the genetic relatedness of the parthenogenetic and bisexual Haemaphysalis longicornis (Acari: Ixodidae)

As an obligate hematophagous ectoparasite, the hard tick Haemaphysalis longicornis exhibits two reproductive strategies, bisexual reproduction, and obligate parthenogenesis, which have attracted a widespread attention. However, the speciation of parthenogenetic population remained ambiguous due to its similarity in morphology but the remarkable differences in cytogenetics as compared with those of the bisexual ones. In the present study, we explored several new lines of genetic evidence to resolve this controversial issue. The number of the chromosomes in two lineages was checked by classical methods and their total DNA levels were determined utilizing flowcytometry. In addition, the sequences of 12S rDNA, 16S rDNA, cytochrome c oxidase I and II (COI, COII) and internal transcribed spacer-2 (ITS-2) genes were used to assess their phylogenetic relationship. We observed that the chromosome ploidy of bisexual and parthenogenetic H. longicornis collected by our laboratory was diploid and triploid, respectively. Flowcytometry analysis indicated a ratio close to 2:3 in the DNA contents of bisexual to parthenogenetic H. longicornis. Although the chromosome ploidy is different, their gene sequences are extremely similar. Analogous to the intra-species genetic difference of other invertebrates, sequence differences of all loci examined are below 2%. Phylogenetic trees constructed from 12S rDNA, 16S rDNA, COI, and ITS-2 genes revealed that they were all in the same monophyletic clade instead of splitting independently into evolutional branches. Moreover, according to 4× Rule, the K/θ ratio of two reproductive populations calculated based on COI was much smaller than four, strongly supporting that they belong to the same species. Therefore, we conclude that the evolutionary process just disturbs the chromosome ploidy and the sexual determination of parthenogenetic population and that it would be better to consider parthenogenetic H. longicornis as a metapopulation rather than a cryptic species.

Characterization of Haemaphysalis flava (Acari: Ixodidae) from Qingling subspecies of giant panda (Ailuropoda melanoleuca qinlingensis) in Qinling Mountains (Central China) by morphology and molecular markers

Tick is one of important ectoparasites capable of causing direct damage to their hosts and also acts as vectors of relevant infectious agents. In the present study, the taxa of 10 ticks, collected from Qinling giant pandas (Ailuropoda melanoleuca qinlingensis) in Qinling Mountains of China in April 2010, were determined using morphology and molecular markers (nucleotide ITS2 rDNA and mitochondrial 16S). Microscopic observation demonstrated that the morphological features of these ticks were similar to Haemaphysalis flava. Compared with other Haemaphysalis species, genetic variations between Haemaphysalis collected from A. m. qinlingensis and H. flava were the lowest in ITS2 rDNA and mitochondrial 16S, with sequence differences of 2.06%–2.40% and 1.30%–4.70%, respectively. Phylogenetic relationships showed that all the Haemaphysalis collected from A. m. qinlingensis were grouped with H. flava, further confirmed that the Haemaphysalis sp. is H. flava. This is the first report of ticks in giant panda by combining with morphology and molecular markers. This study also provided evidence that combining morphology and molecular tools provide a valuable and efficient tool for tick identification.