First glimpse into the origin and spread of the Asian longhorned tick, Haemaphysalis longicornis, in the United States

A broadly protective antibody targeting glycoprotein Gn inhibits severe fever with thrombocytopenia syndrome virus infection

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging bunyavirus that causes severe viral hemorrhagic fever and thrombocytopenia syndrome with a fatality rate of up to 30%. No licensed vaccines or therapeutics are currently available for humans. Here, we develop seven monoclonal antibodies (mAbs) against SFTSV surface glycoprotein Gn. Mechanistic studies show that three neutralizing mAbs (S2A5, S1G3, and S1H7) block multiple steps during SFTSV infection, including viral attachment and membrane fusion, whereas another neutralizing mAb (B1G11) primarily inhibits the viral attachment step. Epitope binning and X-ray crystallographic analyses reveal four distinct antigenic sites on Gn, three of which have not previously been reported, corresponding to domain I, domain II, and spanning domain I and domain II. One of the most potent neutralizing mAbs, S2A5, binds to a conserved epitope on Gn domain I and broadly neutralizes infection of six SFTSV strains corresponding to genotypes A to F. A single dose treatment of S2A5 affords both pre- and post-exposure protection of mice against lethal SFTSV challenge without apparent weight loss. Our results support the importance of glycoprotein Gn for eliciting a robust humoral response and pave a path for developing prophylactic and therapeutic antibodies against SFTSV infection.

New report of Haemaphysalis longicornis (Ixodida: Ixodidae) in Mecklenburg County, Virginia from field collections

Haemaphysalis longicornis (Neumann) was first established in New Jersey and has rapidly spread across most of the eastern United States. This tick has the potential to infest a wide variety of hosts and can reproduce quickly via parthenogenesis, presenting a new threat to animal health. Here we report the first record of a single H. longicornis tick in Mecklenburg County, Virginia, from incidental field collections of ticks. In addition to H. longicornis, we collected 787 Amblyomma americanum, 25 Dermacentor variabilis, 6 Ixodes affinis, 1 Haemaphysalis leporispalustris, and 1 Amblyomma maculatum using standard dragging and flagging techniques. The expansion of H. longicornis will have economic consequences for livestock producers in south-central Virginia, who must now manage this species. Enhanced surveillance is needed to fully understand its growing geographic distribution in the United States and the subsequent consequences of its spread.

Surveillance and detection of Haemaphysalis longicornis (Acari: Ixodidae) in protected areas from Georgia, USA

The invasion of the Asian longhorned tick, Haemaphysalis longicornis Neumann, into the United States poses a significant ecological, veterinarian, and public health threat. We conducted a comprehensive tick survey using standard tick flagging protocol for collection over 3 field seasons, March-August, and 56 surveyed sites to identify the presence of H. longicornis in the native ecosystem and prove its establishment according to USDA criteria. Of the total 56 state parks and wildlife management areas (WMA) surveyed, only one was found to be invaded by H. longicornis; detection of H. longicornis occurred at Buck Shoals Wildlife Management area in White County, GA. This site is maintained by the state of Georgia, has no agricultural animals present, and hosts a large white-tailed deer population. After the initial detection of H. longicornis in 2022, an additional field season occurred in 2023, where H. longicornis was confirmed as established based on USDA criteria. The increase in H. longicornis populations from 2021 to 2023 at Buck Shoals WMA points to the rapid spread of this tick within the environment. Our findings provide evidence of the rapid establishment of H. longicornis in the southern edge of suitability for this tick and within the native ecosystem beyond farmlands and private land.

Haemaphysalis longicornis (Acari: Ixodidae) does not transmit Babesia bovis, a causative agent of cattle fever

The Asian longhorned tick (Haemaphysalis longicornis) was first reported in the United States in 2017 and has since been detected in at least 17 states. This tick infests cattle and can produce large populations quickly due to its parthenogenetic nature, leading to significant livestock mortalities and economic losses. While H. longicornis has not been detected in Texas, species distribution models have identified southern Texas as a possible hospitable region for this tick. Southern Texas is currently home to the southern cattle tick (Rhipicephalus microplus), which can transmit the causative agent of cattle fever (Babesia bovis). With the potential for H. longicornis and B. bovis to overlap in southern Texas and their potential to negatively impact the national and global livestock industry, it is imperative to identify the role H. longicornis may play in the cattle fever disease system. A controlled acquisition and transmission experiment tested whether H. longicornis is a vector for B. bovis, with the R. microplus-B. bovis system used as a positive control. Transstadial (nymphs to adults) and transovarial (adults to larvae) transmission and subsequent transstadial maintenance (nymphs and adults) routes were tested in this study. Acquisition-fed, splenectomized animals were used to increase the probability of tick infection. Acquisition nymphs were macerated whole and acquisition adults were dissected to remove midguts and ovaries at five time points (4, 6, 8, 10, and 12 days post-repletion), with 40 ticks processed per time point and life stage. The greatest percentage of nymphs with detectable B. bovis DNA occurred six days post-repletion (20.0 %). For adults, the percentage of positive midguts and ovaries increased as days post-repletion progressed, with day 12 having the highest percentage of positive samples (67.5 % and 60.0 %, respectively). When egg batches were tested in triplicate, all H. longicornis egg batches were negative for B. bovis, while all R. microplus egg batches were positive for B. bovis. During the transmission phase, the subsequent life stages for transstadial (adults) and transovarial transmission/transstadial maintenance (larvae, nymphs, and adults) were fed on naïve, splenectomized calves. All life stages of H. longicornis ticks tested during transmission were negative for B. bovis. Furthermore, the transmission fed animals were also negative for B. bovis and did not show signs of bovine babesiosis during the 45-day post tick transmission period. Given the lack of successful transstadial or transovarial transmission, it is unlikely that H. longicornis is a vector for B. bovis.

Transboundary Tick and Tick-Borne Pathogen Threats to Cattle

Transboundary incursions of ticks and tick-borne pathogens are ever present concerns for US cattle industries. Global trade in livestock and wildlife, historic and emerging transboundary issues with endemic tick populations and pathogens, and migratory bird flyways are pathways of concern. Transboundary challenges are presented for the Asian long-horned tick and Theileria orientalis Ikeda, for 2 cattle fever tick species [Rhipicephalus (Boophilus) annulatus and R (B) microplus] and Babesia bigemina and B bovis, and for the tropical bont tick and Ehrlichia ruminantium.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Single dose, dual antigen RNA vaccines protect against lethal Crimean-Congo haemorrhagic fever virus infection in mice

BACKGROUND

Crimean-Congo Haemorrhagic Fever Virus is a tick-borne bunyavirus prevalent across Asia, Africa, the Middle East, and Europe. The virus causes a non-specific febrile illness which may develop into severe haemorrhagic disease. To date, there are no widely approved therapeutics. Recently, we reported an alphavirus-based replicon RNA vaccine which expresses the CCHFV nucleoprotein (repNP) or glycoprotein precursor (repGPC) and is protective against lethal disease in mice.

METHODS

Here, we evaluated engineered GPC constructs to find the minimal enhancing epitope of repGPC and test two RNA vaccine approaches to express multiple antigens in vivo to optimize protective efficacy of our repRNA.

FINDINGS

Vaccination with repNP and a construct expressing just the Gc antigen (repGc-FL) resulted in equivalent immunogenicity and protective efficacy compared to original repNP + repGPC vaccination. This vaccine was protective when prepared in either of two vaccine approaches, a mixed synthesis reaction producing two RNAs in a single tube and a single RNA expressing two antigens.

INTERPRETATION

Overall, our data illustrate two vaccine approaches to deliver two antigens in a single immunization. Both approaches induced protective immune responses against CCHFV in this model. These approaches support their continued development for this and future vaccine candidates for CCHFV and other vaccines where inclusion of multiple antigens would be optimal.

FUNDING

This work was supported by the Intramural Research Program, NIAID/NIH, HDT Bio and MCDC Grant #MCDC2204-011.

Data release: targeted systematic literature search for tick and tick-borne pathogen distributions in six countries in sub-Saharan Africa from 1901 to 2020

BACKGROUND

Surveillance data documenting tick and tick-borne disease (TBD) prevalence is needed to develop risk assessments and implement control strategies. Despite extensive research in Africa, there is no standardized, comprehensive review.

METHODS

Here we tackle this knowledge gap, by producing a comprehensive review of research articles on ticks and TBD between 1901 and 2020 in Chad, Djibouti, Ethiopia, Kenya, Tanzania, and Uganda. Over 8356 English language articles were recovered. Our search strategy included 19 related MeSH terms. Articles were reviewed, and 331 met inclusion criteria. Articles containing mappable data were compiled into a standardized data schema, georeferenced, and uploaded to VectorMap.

RESULTS

Tick and pathogen matrixes were created, providing information on vector distributions and tick-pathogen associations within the six selected African countries.

CONCLUSIONS

These results provide a digital, mappable database of current and historical tick and TBD distributions across six countries in Africa, which can inform specific risk modeling, determine surveillance gaps, and guide future surveillance priorities.

A survey of knowledge, attitudes, and practices of veterinary professionals regarding ticks and tick-borne diseases: Insights from Ohio, USA

Globally, ticks are becoming more problematic as agricultural pests and vectors of tick-borne diseases (TBDs), many of which are shared between animals and people. Veterinary professionals, including veterinarians and non-veterinarians, are considered a vulnerable group through occupational exposure. To inform educational interventions at the intrapersonal level, a common approach is to first assess knowledge, attitudes, and practices (KAP) of target populations. Thus, our objective was to assess KAP of veterinary professionals in Ohio, a state faced with expanding and invading ticks of medical and veterinary concern. Using a convenience sample, we surveyed 178 veterinary professionals across Ohio with an electronic questionnaire that covered knowledge, attitudes, practices, exposures, demography, education, and surveillance regarding ticks and TBDs. We found that veterinary professionals had cautionary attitudes towards ticks and TBDs and practiced prevention for themselves and their patients, even when tick exposures were infrequently reported. However, veterinary professionals significantly lacked in knowledge regarding tick biology and local TBD epidemiology. Furthermore, we found that knowledge regarding tick biology and attitudes towards ticks and TBDs did not associate with practices. Instead, we found that veterinarian status and routine tick checks of patients were associated with frequent discussions of tick prevention with clients. Our findings emphasize that most tick exposures of veterinary professionals are occupational, and thus prevention should start at the workplace. Cultivating knowledge of veterinary professionals regarding tick biology and local TBD epidemiology may lead to greater motivation and confidence with identifying ticks and testing for TBDs, which may also increase the diagnostic capacity of veterinary professionals for tick and TBD surveillance. Because veterinary professionals typically interact with both animals and their owners, improving their KAP regarding ticks and TBDs, can in turn promote animal, human, and environmental health within a "One Health" context.

Ticks (Acari: Ixodida) on synanthropic small and medium-sized mammals in areas of the northeastern United States infested with the Asian longhorned tick, Haemaphysalis longicornis

The northeastern United States (US) is a hotspot for tick-borne diseases. Adding to an already complex vector landscape, in 2017 large populations of the invasive Haemaphysalis longicornis, the Asian longhorned tick, were detected in New Jersey (NJ) and later found to be widespread from Connecticut to Georgia. In its native range in northeastern Asia, H. longicornis is considered an important vector of deadly pathogens to humans, companion animals, and livestock. To identify the primary hosts of H. longicornis, we surveyed synanthropic small and medium-sized mammals in three different sites in suburban New Brunswick, NJ. Specifically, we collected approximately 9,000 tick specimens belonging to nine species from 11 different species of mammals sampled between May and September 2021. We found that H. longicornis feeds more frequently on rodents than previously thought, and that this invasive tick is likely exposed to important enzootic and zoonotic pathogens. Overall, we obtained detailed information about the seasonal dynamics and feeding patterns of six tick species common in the northeastern US, Haemaphysalis longicornis, Amblyomma americanum, Dermacentor variabilis, Ixodes scapularis, Ixodes texanus and Ixodes cookei. We found that unlike I. scapularis that feeds on mammals of all sizes, H. longicornis feeds on hosts following the general pattern of A. americanum, favoring larger species such as skunks, groundhogs, and raccoons. However, our survey revealed that unlike A. americanum, H. longicornis reaches high densities on Virginia opossum. Overall, the newly invasive H. longicornis was the most numerous tick species, both on multiple host species and in the environment, raising significant questions regarding its role in the epidemiology of tick-borne pathogens, especially those affecting livestock, companion animals and wildlife. In conclusion, our findings provide valuable insights into the tick species composition on mammalian hosts in NJ and the ongoing national expansion of H. longicornis.

Comparison of the initial and residual speed of Ixodes scapularis kill on dogs treated with a single dose of Bravecto® Chew (25 mg/kg fluralaner) or Simparica TRIO® (1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel)

BACKGROUND

Compliant ectoparasiticide product use is a comprehensive way to control ticks and reduce the risk of tick-borne pathogen transmission to dogs. Because the systemically acting isoxazoline ectoparasiticides require tick attachment for drug delivery, fast speed of kill is essential to minimize tick-borne pathogen transmission risk.

METHODS

Dogs of satisfactory tick-carrying capacity were randomly allocated to treatment groups and administered, per label instructions, Bravecto® Chews (minimum 25 mg/kg fluralaner), Simparica TRIO® (minimum 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel), or no treatment. Dogs were infested with approximately 50 unfed adult (35 female, 15 male) Ixodes scapularis on Day -2, 21 and 28. Live tick counts were performed at 4, 8, 12 and 24 h post-treatment (Day 0) and post-infestation on Day 21 and 28. Tick control efficacy was determined by comparing live tick means for each product-treated group to the untreated control group and each other at all time points using a linear mixed model. The percent of dogs free of live ticks was analyzed using the Fisher's exact test for treatment group comparison.

RESULTS

The untreated control group maintained adequate tick infestations throughout the study. Using geometric means, an existing I. scapularis infestation was controlled by 99.7% and 93.0% 12 h post-treatment and by 100% and 99.5% 24 h post-treatment, for Bravecto® and Simparica TRIO®-treated dogs, respectively. Ixodes scapularis infestations were controlled more quickly for Bravecto®- compared to Simparica TRIO®-treated dogs on Day 21 at 8 h (efficacy 74.0% vs. 0.0%, p = 0.003) and 12 h (efficacy 99.2% vs. 39.4%, p < 0.001) post-infestation and Day 28 at 8 h (efficacy 92.2% vs. 0.0%, p < 0.001) and 12 h (efficacy 99.6% vs. 27.7%, p < 0.001) post-infestation. On Day 28 post-treatment, the efficacy of Bravecto® and Simparica TRIO® to control a new I. scapularis infestation was 100% and 96.6%, respectively, by 24 h post-infestation. Of product-treated dogs, 100% of Bravecto®-treated dogs were free of live ticks by 24 h post-treatment or post-infestation. No treatment-related adverse reactions occurred during the study.

CONCLUSIONS

Ixodes scapularis infestations are controlled more quickly 21 and 28 days post-treatment for dogs administered a single dose of Bravecto® compared to dogs administered a single dose of Simparica TRIO®.

Describing the experience of livestock producers from Ohio, USA with ticks and associated diseases

BACKGROUND

As tick ranges expand across North America, the risk of tick bites and tick-borne diseases (TBDs, i.e. diseases or syndromes associated with ticks) rises for humans and animals, making prevention critical. Several U.S. studies have examined knowledge, attitudes, and practices regarding ticks and TBDs for various cohorts of people. However, among occupational groups with high exposure risk from ticks and TBDs are livestock producers, of which we know little about. To help address this gap, an electronic questionnaire was distributed to livestock producers in Ohio, U.S, a state with a robust agricultural sector.

METHODS

We generated descriptive statistics and conducted a multiple correspondence analysis followed by hierarchical clustering on principal components to identify producers with similar response profiles.

RESULTS

Responses from 57 producers showed that most (52.6%) think the American dog tick (Dermacentor variabilis) is found in Ohio but are unsure about other species. Although several TBDs are present in Ohio, most (> 50%) producers were unsure or unaware of their presence. Interestingly, most (54.4%) thought ticks pose major health risks for their livestock but fewer (49.1%) thought the same for humans. Regardless, most producers did employ at least one prevention method for themselves (96.5%) and their animals (82.5%). Cluster analysis (n = 48) identified three groups: the largest (n = 21) was considered "aware and cautious" consisting primarily of farm owners. The others generally practiced less prevention and consisted primarily of farm employees.

CONCLUSIONS

Our findings indicate that producers in Ohio practice prevention for themselves and their livestock, but demonstrate gaps in knowledge (e.g., TBD occurrence) and attitudes (e.g., health risks) that could be addressed via educational formats we found producers preferred (e.g., extension materials), to encourage informed prevention. This is especially important for farm employees that may practice less prevention because of lower awareness. Our study can guide others in regions faced with similar tick and TBD risks to protect occupational and livestock health.

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.

Baseline susceptibility of Haemaphysalis longicornis to organophosphate, carbamate, and pyrethroid acaricides

BACKGROUND

The Asian longhorned tick, Haemaphysalis longicornis, continues to expand its range in North America, and synthetic acaricides are likely to play an increasing role in managing this species. Acaricide resistance is common in some tick species that infest livestock. However, baseline acaricide susceptibility has not previously been examined in this invasive tick.

RESULTS

We used a standard larval packet test to evaluate the susceptibility of the Asian longhorned tick to acaricides currently or formerly used in tick control: propoxur, carbaryl, bifenthrin, permethrin, and coumaphos. Discriminating concentrations were estimated at 6.5, 27.9, 988, 2242, and 808 ppm, respectively. The half-maximal lethal concentration (LC50 ) values for propoxur, carbaryl, permethrin and coumaphos were compared with data available for other tick species and showed that H. longicornis was more susceptible to propoxur, carbaryl and coumaphos, and had a similar susceptibility to permethrin.

CONCLUSIONS

The results indicate that resistance to these acaricides is not currently a concern for H. longicornis in the United States. However, responsible integrated management and early detection of resistance can help ensure the long-term efficacy of products used for controlling this tick species. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Transfusion-transmitted Babesia spp.: a changing landscape of epidemiology, regulation, and risk mitigation

Babesia spp. are tick-borne parasites with a global distribution and diversity of vertebrate hosts. Over the next several decades, climate change is expected to impact humans, vectors, and vertebrate hosts and change the epidemiology of Babesia. Although humans are dead-end hosts for tick-transmitted Babesia, human-to-human transmission of Babesia spp. from transfusion of red blood cells and whole blood-derived platelet concentrates has been reported. In most patients, transfusion-transmitted Babesia (TTB) results in a moderate-to-severe illness. Currently, in North America, most cases of TTB have been described in the United States. TTB cases outside North America are rare, but case numbers may change over time with increased recognition of babesiosis and as the epidemiology of Babesia is impacted by climate change. Therefore, TTB is a concern of microbiologists working in blood operator settings, as well as in clinical settings where transfusion occurs. Microbiologists play an important role in deploying blood donor screening assays in Babesia endemic regions, identifying changing risks for Babesia in non-endemic areas, investigating recipients of blood products for TTB, and drafting TTB policies and guidelines. In this review, we provide an overview of the clinical presentation and epidemiology of TTB. We identify approaches and technologies to reduce the risk of collecting blood products from Babesia-infected donors and describe how investigations of TTB are undertaken. We also describe how microbiologists in Babesia non-endemic regions can assess for changing risks of TTB and decide when to focus on laboratory-test-based approaches or pathogen reduction to reduce TTB risk.

Ticks and tick-borne microbes identified through passive and active surveillance in Alaska

Rapid environmental change in Alaska and other regions of the Arctic and sub-Arctic has raised concerns about increasing human exposure to ticks and the pathogens they carry. We tested a sample of ticks collected through a combination of passive and active surveillance from humans, domestic animals, and wildlife hosts in Alaska for a panel of the most common tick-borne pathogens in the contiguous United States to characterize the diversity of microbes present in this region. We tested 189 pooled tick samples collected in 2019-2020 for Borrelia spp., Anaplasma spp., Ehrlichia spp., and Babesia spp. using a multiplex PCR amplicon sequencing assay. We found established populations of Ixodes angustus Neumann (Acari: Ixodidae), Ixodes uriae White (Acari: Ixodidae), and Haemaphysalis leporispalustris Packard (Acari: Ixodidae) in Alaska, with I. angustus found on a variety of hosts including domestic companion animals (dogs and cats), small wild mammals, and humans. Ixodes angustus were active from April through October with peaks in adult and nymphal activity observed in summer months (mainly July). Although no known human pathogens were detected, Babesia microti-like parasites and candidatus Ehrlichia khabarensis were identified in ticks and small mammals. The only human pathogen detected (B. burgdorferi s.s.) was found in a tick associated with a dog that had recently traveled to New York, where Lyme disease is endemic. This study highlights the value of a combined passive and active tick surveillance system to detect introduced tick species and pathogens and to assess which tick species and microbes are locally established.

Rabbits as Animal Models for Anti-Tick Vaccine Development: A Global Scenario

Studies evaluating candidate tick-derived proteins as anti-tick vaccines in natural hosts have been limited due to high costs. To overcome this problem, animal models are used in immunization tests. The aim of this article was to review the use of rabbits as an experimental model for the evaluation of tick-derived proteins as vaccines. A total of 57 tick proteins were tested for their immunogenic potential using rabbits as models for vaccination. The most commonly used rabbit breeds were New Zealand (73.8%), Japanese white (19%), Californians (4.8%) and Flemish lop-eared (2.4%) rabbits. Anti-tick vaccines efficacy resulted in up to 99.9%. Haemaphysalis longicornis (17.9%) and Ornithodoros moubata (12.8%) were the most common tick models in vaccination trials. Experiments with rabbits have revealed that some proteins (CoAQP, OeAQP, OeAQP1, Bm86, GST-Hl, 64TRP, serpins and voraxin) can induce immune responses against various tick species. In addition, in some cases it was possible to determine that the vaccine efficacy in rabbits was similar to that of experiments performed on natural hosts (e.g., Bm86, IrFER2, RmFER2, serpins and serine protease inhibitor). In conclusion, results showed that prior to performing anti-tick vaccination trials using natural hosts, rabbits can be used as suitable experimental models for these studies.

Detection of multiple tick-borne pathogens in Ixodes scapularis from Hunterdon County, NJ, USA

Several human pathogens vectored by the blacklegged tick (Ixodes scapularis Say; Acari: Ixodidae) are endemic in the state of New Jersey. Disease incidence data suggest that these conditions occur disproportionately in the northwestern portion of the state, including in the county of Hunterdon. We conducted active surveillance at three forested sites in Hunterdon County during 2020 and 2021, collecting 662 nymphal and adult I. scapularis. Ticks were tested for five pathogens by qPCR/qRT-PCR: Anaplasma phagocytophilum, Babesia microti, Borrelia burgdorferi, Borrelia miyamotoi, and Powassan virus (POWV) lineage 2. Over 2 years, 25.4% of nymphs and 58.4% of adults were found infected with at least one pathogen, with 10.6% of all ticks infected with more than one pathogen. We report substantial spatial and temporal variability of A. phagocytophilum and B. burgdorferi, with high relative abundance of the human-infective A. phagocytophilum variant Ap-ha. Notably, POWV was detected for the first time in Hunterdon, a county where human cases have not been reported. Based on comparisons with active surveillance initiatives in nearby counties, further investigation of non-entomological factors potentially influencing rates of tick-borne illness in Hunterdon is recommended.

Draft genome sequence data of Haemaphysalis longicornis Oita strain

Haemaphysalis longicornis Neumann, 1901 is one of the most well-known hard ticks because of its medical and veterinary importance. Haemaphysalis longicornis transmit a wide range of pathogens among vertebrates, affecting humans and animals in Asia and Oceania. In Japan, the tick species is a major pest of cattle because it can spread a protozoan parasite Theileria orientalis, which causes theileriosis and produces economic losses to the livestock industry (Yokoyama et al. 2012 [1]). Apart from bovine theileriosis, H. longicornis is a vector of bovine babesiosis caused by Babesia ovata, canine babesiosis caused by Babesia gibsoni, and rickettsiosis and viral diseases in humans. Its habitats are mainly Japan, Australia, New Zealand, New Caledonia, the Fiji Islands, Korea, China, and Russia (Oliver et al. 1973 [2]). In the United States, heavy H. longicornis infestations on cattle and white-tailed deer were reported in 2019, making it now one of the tick species to be an increasing threat to livestock animals and humans globally. Ticks reproduce offspring after mating with female and male ticks, however, interestingly, there are two races of H. longicornis: bisexual (diploid) and parthenogenetic (triploid) races [2]. Parthenogenetic H. longicornis is distributed throughout Japan, while the northern limit of the bisexual race is believed to be Fukushima Prefecture on Honshu Island (Fujita et al. 2013 and Kitaoka et al. 1961 [3,4]). This tick species is also considered to be of great scientific importance, and the parthenogenetic race collected in Okayama prefecture has been reared since 1961, while the bisexual race collected in Oita prefecture has been reared since 2008 under laboratory conditions in Japan (Boldbaatar et al. 2010 and Fujisaki et al. 1976 [5,6]). Namely, the "Okayama strain" and "Oita strain" of H. longicornis have been maintained for more than six decades and 15 years, respectively, stably under laboratory conditions. To obtain reference data of bisexual H. longicornis, we sequenced unfed females with haploid genomes using Illumina and MinION Q20 kit then obtained a draft genome consisting of 2.48 Gbp. The number of the contig was 98,529 and N50 was 46.5 Kb. Genome information derived from our laboratory colony of bisexual H. longicornis ticks would provide fundamental insight into understanding how different reproductive lineages occur within the same species of the tick.

Identification and Characterization of Rhipicephalus microplus ATAQ Homolog from Haemaphysalis longicornis Ticks and Its Immunogenic Potential as an Anti-Tick Vaccine Candidate Molecule

Although vaccines are one of the environmentally friendly means to prevent the spread of ticks, there is currently no commercial vaccine effective against Haemaphysalis longicornis ticks. In this study, we identified, characterized, localized, and evaluated the expression patterns, and tested the immunogenic potential of a homologue of Rhipicephalus microplus ATAQ in H. longicornis (HlATAQ). HlATAQ was identified as a 654 amino acid-long protein present throughout the midgut and in Malpighian tubule cells and containing six full and one partial EGF-like domains. HlATAQ was genetically distant (homology < 50%) from previously reported ATAQ proteins and was expressed throughout tick life stages. Its expression steadily increased (p < 0.001) during feeding, reached a peak, and then decreased slightly with engorgement. Silencing of HlATAQ did not result in a phenotype that was significantly different from the control ticks. However, H. longicornis female ticks fed on a rabbit immunized with recombinant HlATAQ showed significantly longer blood-feeding periods, higher body weight at engorgement, higher egg mass, and longer pre-oviposition and egg hatching periods than control ticks. These findings indicate that the ATAQ protein plays a role in the blood-feeding-related physiological processes in the midgut and Malpighian tubules and antibodies directed against it may affect these tissues and disrupt tick engorgement and oviposition.

Rapid invasion and expansion of the Asian longhorned tick (Haemaphysalis longicornis) into a new area on Long Island, New York, USA

Since its discovery in the United States in 2017, the Asian longhorned tick (Haemaphysalis longicornis) has been detected in most eastern states between Rhode Island and Georgia. Long Island, east of New York City, a recognized high-risk area for tick-borne diseases, is geographically close to New Jersey and New York sites where H. longicornis was originally found. However, extensive tick surveys conducted in 2018 did not identify H. longicornis on Long Island. In stark contrast, our 2022 tick survey suggests that H. longicornis has rapidly invaded and expanded in multiple surveying sites on Long Island (12 out of 17 sites). Overall, the relative abundance of H. longicornis was similar to that of lone star ticks, Amblyomma americanum, a previously recognized tick species abundantly present on Long Island. Interestingly, our survey suggests that H. longicornis has expanded within the Appalachian forest ecological zone of Long Island's north shore compared to the Pine Barrens located on the south shore of Long Island. The rapid invasion and expansion of H. longicornis into an insular environment are different from the historical invasion and expansion of two native tick species, Ixodes scapularis (blacklegged tick or deer tick) and A. americanum, in Long Island. The implications of H. longicornis transmitting or introducing tick-borne pathogens of public health importance remain unknown.

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.

Microhabitat modeling of the invasive Asian longhorned tick (Haemaphysalis longicornis) in New Jersey, USA

The Asian longhorned tick (Haemaphysalis longicornis) is a vector of multiple arboviral and bacterial pathogens in its native East Asia and expanded distribution in Australasia. This species has both bisexual and parthenogenetic populations that can reach high population densities under favorable conditions. Established populations of parthenogenetic H. longicornis were detected in the eastern United States in 2017 and the possible range of this species at the continental level (North America) based on climatic conditions has been modeled. However, little is known about factors influencing the distribution of H. longicornis at geographic scales relevant to local surveillance and control. To examine the importance of local physiogeographic conditions such as geology, soil characteristics, and land cover on the distribution of H. longicornis we employed ecological niche modeling using three machine learning algorithms - Maxent, Random Forest (RF), and Generalized Boosting Method (GBM) to estimate probability of finding H. longicornis in a particular location in New Jersey (USA), based on environmental predictors. The presence of H. longicornis in New Jersey was positively associated with Piedmont physiogeographic province and two soil types - Alfisols and Inceptisols. Soil hydraulic conductivity was the most important predictor explaining H. longicornis habitat suitability, with more permeable sandy soils with higher hydraulic conductivity being less suitable than clay or loam soils. The models were projected over the state of New Jersey creating a probabilistic map of H. longicornis habitat suitability at a high spatial resolution of 90×90 meters. The model's sensitivity was 87% for locations sampled in 2017-2019 adding to the growing evidence of the importance of soil characteristics to the survival of ticks. For the 2020-2022 dataset the model fit was 57%, suggestive of spillover to less optimal habitats or, alternatively, heterogeneity in soil characteristics at the edges of broad physiographic zones. Further modeling should incorporate abundance and life-stage information as well as detailed characterization of the soil at collection sites. Once critical parameters that drive the survival and abundance of H. longicornis are identified they can be used to guide surveillance and control strategies for this invasive species.

Tick Control in a Connected World: Challenges, Solutions, and Public Policy from a United States Border Perspective

Ticks are able to transmit the highest number of pathogen species of any blood-feeding arthropod and represent a growing threat to public health and agricultural systems worldwide. While there are numerous and varied causes and effects of changes to tick-borne disease (re)emergence, three primary challenges to tick control were identified in this review from a U.S. borders perspective. (1) Climate change is implicated in current and future alterations to geographic ranges and population densities of tick species, pathogens they can transmit, and their host and reservoir species, as highlighted by Ixodes scapularis and its expansion across southern Canada. (2) Modern technological advances have created an increasingly interconnected world, contributing to an increase in invasive tick species introductions through the increased speed and frequency of trade and travel. The introduction of the invasive Haemaphysalis longicornis in the eastern U.S. exemplifies the challenges with control in a highly interconnected world. (3) Lastly, while not a new challenge, differences in disease surveillance, control, and management strategies in bordering countries remains a critical challenge in managing ticks and tick-borne diseases. International inter-agency collaborations along the U.S.-Mexico border have been critical in control and mitigation of cattle fever ticks (Rhipicephalus spp.) and highlight the need for continued collaboration and research into integrated tick management strategies. These case studies were used to identify challenges and opportunities for tick control and mitigation efforts through a One Health framework.

First Detection of the Invasive Asian Longhorned Tick (Acari: Ixodidae) on Migratory Passerines in the Americas

The Asian longhorned tick (Haemaphysalis longicornis Neumann), native to East Asia, was first reported in the United States in 2017 and is now established in at least 17 states. Haemaphysalis longicornis feeds on birds in its range outside of the United States, and migratory birds disperse this tick and tick-borne pathogens. However, early studies in the United States did not find H. longicornis on migrating passerine birds. The transport of the parthenogenetic H. longicornis on birds has the potential to greatly expand its range. We report the first discovery of H. longicornis on migratory passerine birds in the Americas.

Human social conditions predict the risk of exposure to zoonotic parasites in companion animals in East and Southeast Asia

Background

A recent dramatic surge in pet ownership has been observed across metropolitan areas in Asia. To date, there is a dearth of information on the risk associated with pet ownership for the transmission of parasites on a large scale in Asia, despite this continent giving rise to the largest burden of zoonotic infections worldwide.

Methods

We explored the nature and extent of zoonotic internal (endo-) and external (ecto-) parasites and arthropod-borne pathogens in 2381 client-owned dogs and cats living in metropolitan areas of eight countries in East and Southeast Asia using reliable diagnostic tests and then undertook extensive statistical analyses to define predictors of exposure to zoonotic pathogens.

Results

The estimated ORs for overall parasite infections are 1.35 [95% CIs 1.07;1.71] in young animals and 4.10 [1.50;11.2] in the animal group older than 15 years as compared with adult animals, 0.61 [0.48;0.77] in neutered animals as compared to unneutered animals, 0.36 [0.26;0.50] in animals living in urban areas as compared with rural areas, 1.14 [1.08;1.21] for each 1 °C increase of annual mean temperature which varies from 12.0 to 28.0 °C, and 0.86 [0.78;0.95] for each year of life expectancy which varies from 70.9 to 83.3 years.

Conclusions

Here we highlight the influence of human life expectancy and the neutering status of the animals, which reflect increased living standards through access to education and human and veterinary health care, to be both strongly associated with exposure to zoonotic parasites. An integrated approach of local and international authorities to implement and manage educational programs will be crucial for the control of zoonotic infections of companion animals in Asia.

Parasites live on or inside animals or humans and can cause disease. Companion animals (pets) with parasites present a potential risk to the health of their owners, as certain kinds of parasites (known as zoonotic parasites) can affect both animal and human health. Here, we investigated whether human social conditions are associated with zoonotic parasite infections in companion animals in East and Southeast Asia. We found that higher human life expectancy and neutering of the companion animals were associated with fewer zoonotic parasite infections in the animals. These findings highlight the need for an enhanced commitment of local authorities to establish prevention campaigns, including education programs, against zoonotic pathogens. These measures will play a crucial role in alleviating the impact of these diseases in companion animals and humans in Asia.

Colella, Wongnak et al. test pet dogs and cats from metropolitan areas of eight countries in East and Southeast Asia for zoonotic parasites. The authors identify factors associated with potential exposure to zoonotic parasites, including animal characteristics and human living conditions.

Can restoration of fire-dependent ecosystems reduce ticks and tick-borne disease prevalence in the eastern United States?

Over the past century, fire suppression has facilitated broad ecological changes in the composition, structure, and function of fire-dependent landscapes throughout the eastern US, which are in decline. These changes have likely contributed mechanistically to the enhancement of habitat conditions that favor pathogen-carrying tick species, key wildlife hosts of ticks, and interactions that have fostered pathogen transmission among them and to humans. While the long-running paradigm for limiting human exposure to tick-borne diseases focuses responsibility on individual prevention, the continued expansion of medically important tick populations, increased incidence of tick-borne disease in humans, and emergence of novel tick-borne diseases highlights the need for additional approaches to stem this public health challenge. Another approach that has the potential to be a cost-effective and widely applied but that remains largely overlooked is the use of prescribed fire to ecologically restore degraded landscapes that favor ticks and pathogen transmission. We examine the ecological role of fire and its effects on ticks within the eastern United States, especially examining the life cycles of forest-dwelling ticks, shifts in regional-scale fire use over the past century, and the concept that frequent fire may have helped moderate tick populations and pathogen transmission prior to the so-called fire-suppression era that has characterized the past century. We explore mechanisms of how fire and ecological restoration can reduce ticks, the potential for incorporating the mechanisms into the broader strategy for managing ticks, and the challenges, limitations, and research needs of prescribed burning for tick reduction.

The wild life of ticks: Using passive surveillance to determine the distribution and wildlife host range of ticks and the exotic Haemaphysalis longicornis, 2010-2021

Background

We conducted a large-scale, passive regional survey of ticks associated with wildlife of the eastern United States. Our primary goals were to better assess the current geographical distribution of exotic Haemaphysalis longicornis and to identify potential wild mammalian and avian host species. However, this large-scale survey also provided valuable information regarding the distribution and host associations for many other important tick species that utilize wildlife as hosts.

Methods

Ticks were opportunistically collected by cooperating state and federal wildlife agencies. All ticks were placed in the supplied vials and host information was recorded, including host species, age, sex, examination date, location (at least county and state), and estimated tick burden. All ticks were identified to species using morphology, and suspect H. longicornis were confirmed through molecular techniques.

Results

In total, 1940 hosts were examined from across 369 counties from 23 states in the eastern USA. From these submissions, 20,626 ticks were collected and identified belonging to 11 different species. Our passive surveillance efforts detected exotic H. longicornis from nine host species from eight states. Notably, some of the earliest detections of H. longicornis in the USA were collected from wildlife through this passive surveillance network. In addition, numerous new county reports were generated for Amblyomma americanum, Amblyomma maculatum, Dermacentor albipictus, Dermacentor variabilis, and Ixodes scapularis.

Conclusions

This study provided data on ticks collected from animals from 23 different states in the eastern USA between 2010 and 2021, with the primary goal of better characterizing the distribution and host associations of the exotic tick H. longicornis; however, new distribution data on tick species of veterinary or medical importance were also obtained. Collectively, our passive surveillance has detected numerous new county reports for H. longicornis as well as I. scapularis. Our study utilizing passive wildlife surveillance for ticks across the eastern USA is an effective method for surveying a diversity of wildlife host species, allowing us to better collect data on current tick distributions relevant to human and animal health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05425-1.

Recovery of Partially Engorged Haemaphysalis longicornis (Acari: Ixodidae) Ticks from Active Surveillance

The invasive Asian longhorned tick, Haemaphysalis longicornis, has rapidly spread across the northeastern United States and is associated with pathogens of public health and veterinary concern. Despite its importance in pathogen dynamics, H. longicornis blood-feeding behavior in nature, specifically the likelihood of interrupted feeding, remains poorly documented. Here, we report the recovery of partially engorged, questing H. longicornis from active tick surveillance in Pennsylvania. Significantly more engorged H. longicornis nymphs (1.54%) and adults (3.07%) were recovered compared to Ixodes scapularis nymphs (0.22%) and adults (zero). Mean Scutal Index difference between unengorged and engorged nymph specimens was 0.65 and 0.42 for I. scapularis and H. longicornis, respectively, suggesting the questing, engorged H. longicornis also engorged to a comparatively lesser extent. These data are among the first to document recovery of engorged, host-seeking H. longicornis ticks and provide initial evidence for interrupted feeding and repeated successful questing events bearing implications for pathogen transmission and warranting consideration in vector dynamics models.

The Gulf Coast Tick, Amblyomma maculatum (Ixodida: Ixodidae), and Spotted Fever Group Rickettsia in the Highly Urbanized Northeastern United States

We report the multi-year collection of the Gulf Coast tick, Amblyomma maculatum Koch (Acaridae: Ixodida: Ixodidae) in Staten Island, New York City (NYC) as well as their detection in Brooklyn, NYC, and in Atlantic and Cumberland counties in southern New Jersey, USA. The first and most common detections were of adults, however in Freshkills Park on Staten Island larvae were also collected in a following year. The presence of larvae indicates that adults are successfully finding hosts in Staten Island. While it is still unknown how A. americanum reached Staten Island, immatures of this species often parasitize migratory birds, which are now often seen in Freshkills Park. We describe the landscape features of the area in Staten Island where populations were highest and larvae were detected, which could have facilitated the establishment of A. maculatum. Notably, we also report the presence of human pathogens Rickettsia parkeri in 5/10 (50%) of adults tested and R. felis in 1/24 (4.17%) of larvae tested. In addition to established populations in Staten Island we found evidence of A. maculatum in NJ and other NYC boroughs, suggesting current or future establishment is possible. The failure thus far to detect established populations in these areas may be due to inherent difficulties in detecting low density, spatially heterogeneous incipient populations, which could require targeted surveillance efforts for this species. We discuss the consequences to public health of the establishment of A. maculatum and detection of two additional rickettsial pathogens in the densely populated northeastern United States.

Development of a Taqman Real-Time PCR for the Identification of Haemaphysalis longicornis (Acari: Ixodidae)

Haemaphysalis longicornis Neumann, a vector of various pathogens with medical and veterinary importance, is a recent invasive species in the United States. Like many tick species, discerning H. longicornis from congeners can be a challenge. To overcome the difficulty of morphological identification, a Taqman quantitative real-time PCR based on the internal transcribed spacer gene (ITS2) was developed for quick and accurate identification of H. longicornis with a detection limit of as low as 19.8 copies. We also applied the assay to 76,004 archived ticks and found 37 ticks were H. longicornis. One H. longicornis was submitted from Warren, Somerset County, New Jersey in June 2015, 2 yr earlier than the initial report from the United States. None of these 37 H. longicornis was positive for Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato, B. miyamotoi, B. mayonii, Babesia microti, or Ehrlichia muris-like agent.

Will new ticks invade North America? How to identify future invaders

Invasive tick species and the pathogens they transmit pose increasing threats to human and animal health around the world. Little attention has been paid to the characteristics enabling tick species to invade. Here we analyze examples of tick invasion events in North America to identify factors that facilitated the invasion. Commonalities among invasive ticks are that they thrive in anthropogenically modified habitats, feed on either domestic animals or wildlife occurring in high density, and can survive across a broad range of climatic conditions. Invasive tick species varied widely in life history and reproductive habits, suggesting that invasion occurs when multiple characteristics converge. The combination of potential characteristics leading to invasion, however, improves our ability to predict future invaders and inform surveillance.

Seasonality of Ticks and Prevalence of Rickettsiae Species in Dermacentor variabilis and Amblyomma maculatum Across Oklahoma Pastures

Tick-borne diseases are an increasing concern for people and companion animals in the United States, but there is a need for continued vigilance regarding livestock in pasture systems. The south-central United States has some of the highest incidences of tick-borne diseases, and there is a need to re-examine the ecology of tick vectors in relation to pasture systems and livestock. The objective of this study was to establish a baseline of seasonal activity for tick species in diverse regional Oklahoma pastures and screen for important pathogens in Dermacentor variabilis (Say) and Amblyomma maculatum Koch group that may impact livestock and human health. Between 2015 and 2017, transects in five pastures across Oklahoma were visited each month. DNA extracted from adult D. variabilis and A. maculatum group was tested for the presence of bacterial pathogens. We found that tick communities in pastures across Oklahoma differ by season, abundance, and bacterial presence and prevalence. The peak abundance of Amblyomma americanum (L.) adults and nymphs occurred a month earlier over the 2 yr of the study compared with historical studies in the same regions. Additionally, we observed notable differences in peak activity between A. americanum adults and nymphs collected in pastures in central Oklahoma (April) versus pastures in northern part of the state (May). We detected Rickettsia parkeri, R. bellii, and Anaplasma sp. DNA in D. variabilis from pastures across the state. These results potentially have important ramifications for human and livestock risk of encountering infected ticks in pastures across the southern Great Plains.

The distribution of Dermacentor reticulatus in the Czech Republic re-assessed: citizen science approach to understanding the current distribution of the Babesia canis vector

Background

The range of the ornate dog tick Dermacentorreticulatus is rapidly expanding in Europe. This tick species is the vector of canine babesiosis, caused by Babesiacanis, and also plays a role in the transmission of Theileriaequi and Babesiacaballi in equids.

Methods

The geographic range of D.reticulatus in the Czech Republic was re-assessed, and an up-to-date distribution map is presented based on material and data obtained during a nationwide citizen science campaign. Received and flagged individuals of D.reticulatus were also analysed for the presence of B.canis DNA.

Results

In striking contrast to historical records, D.reticulatus was found in all regions of the Czech Republic, with most reports coming from the southeast and northwest of the country. Between February 2018 and June 2021, the project team received 558 photo reports of ticks and 250 packages containing ticks. Of the former, 71.1% were identified as Dermacentor sp. with the remainder identified as Ixodes sp., Haemaphysalis sp., Argas sp. or Hyalomma sp. The majority of specimens in the subset of ticks that were received (N = 610) were D.reticulatus (N = 568, 93.7%), followed by Ixodesricinus and Hyalomma spp. A total of 783 adult D.reticulatus, either received (568) or collected by flagging (215), were tested for the presence of B.canis DNA using species-specific nested PCR targeting part of the 18S rRNA gene; B.canis DNA was demonstrated in 22 samples (2.81%).

Conclusions

The continuous spread of D.reticulatus in the Czech Republic was documented in this study. In addition, DNA of B.canis was also detected in a number of ticks, suggesting the establishment of B.canis in the Czech Republic. These results suggest that veterinarians need to consider the possibility of canine babesiosis even in dogs without a history of travel.

Graphical Abstract

Transovarial Transmission of Heartland Virus by Invasive Asian Longhorned Ticks under Laboratory Conditions

We demonstrated experimental acquisition and transmission of Heartland bandavirus by Haemaphysalis longicornis ticks. Virus was detected in tick salivary gland and midgut tissues. A total of 80% of mice exposed to 1 infected tick seroconverted, suggesting horizontal transmission. H. longicornis ticks can transmit the virus in the transovarial mode.

Rapid Spread of Severe Fever with Thrombocytopenia Syndrome Virus by Parthenogenetic Asian Longhorned Ticks

Severe fever with thrombocytopenia syndrome virus (SFTSV) is spreading rapidly in Asia. This virus is transmitted by the Asian longhorned tick (Haemaphysalis longicornis), which has parthenogenetically and sexually reproducing populations. Parthenogenetic populations were found in ≥15 provinces in China and strongly correlated with the distribution of severe fever with thrombocytopenia syndrome cases. However, distribution of these cases was poorly correlated with the distribution of populations of bisexual ticks. Phylogeographic analysis suggested that the parthenogenetic population spread much faster than bisexual population because colonization is independent of sexual reproduction. A higher proportion of parthenogenetic ticks was collected from migratory birds captured at an SFTSV-endemic area, implicating the contribution to the long-range movement of these ticks in China. The SFTSV susceptibility of parthenogenetic females was similar to that of bisexual females under laboratory conditions. These results suggest that parthenogenetic Asian longhorned ticks, probably transported by migratory birds, play a major role in the rapid spread of SFTSV.

First detection of human pathogenic variant of Anaplasma phagocytophilum in field-collected Haemaphysalis longicornis, Pennsylvania, USA

The Asian longhorned tick, Haemaphysalis longicornis, an invasive species associated with human pathogens, has spread rapidly across the eastern USA. Questing H. longicornis ticks recovered from active surveillance conducted from 1 May to 6 September, 2019 throughout Pennsylvania were tested for rickettsial pathogens. Of 265 ticks tested by PCR for pathogens, 4 (1.5%) were positive for Anaplasma phagocytophilum. Sequence analysis of the 16S rRNA gene confirmed two positives as A. phagocytophilum-human agent variant. This is the first reported detection of A. phagocytophilum-human pathogenic strain DNA in exotic H. longicornis collected in the USA.

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.

Spray and Pour-On Acaricides Killed Tennessee (United States) Field-Collected Haemaphysalis longicornis Nymphs (Acari: Ixodidae) in Laboratory Bioassays

Haemaphysalis longicornis Neumann (Asian longhorned tick) is an exotic and invasive tick species presenting a health and economic threat to the United States (U.S.) cattle industry due to its ability to transmit pathogens and infest hosts in large numbers. The objective of this study was to evaluate available products at causing H. longicornis mortality in a laboratory bioassay. The efficacy of products was evaluated at label rates using H. longicornis nymphs collected from a cattle farm in eastern Tennessee in two different bioassays (spray or dip) against untreated controls. After exposure, ticks were transferred to clean petri dishes and checked for mortality at 0, 1, 2, 3, 4, 21, 24, and 48 h post exposure. No mortality occurred in the untreated controls, whereas all treated ticks were dead within 24 h of exposure (P < 0.0001). These findings support the hypothesis that currently available spray and pour-on products are effective at causing H. longicornis mortality. We conclude that these acaricides can be used as a component to prevent H. longicornis dispersal and for control in the U.S.

Effect of Vegetation on the Abundance of Tick Vectors in the Northeastern United States: A Review of the Literature

Tick-borne illnesses have been on the rise in the United States, with reported cases up sharply in the past two decades. In this literature review, we synthesize the available research on the relationship between vegetation and tick abundance for four tick species in the northeastern United States that are of potential medical importance to humans. The blacklegged tick (Ixodes scapularis) (Say; Acari: Ixodidae) is found to be positively associated with closed canopy forests and dense vegetation thickets, and negatively associated with open canopy environments, such as grasslands or old agricultural fields. The American dog tick (Dermacentor variabilis) (Say; Acari: Ixodidae) has little habitat overlap with I. scapularis, with abundance highest in grasses and open-canopy fields. The lone star tick (Amblyomma americanum) (Linnaeus; Acari: Ixodidae) is a habitat generalist without consistent associations with particular types of vegetation. The habitat associations of the recently introduced Asian longhorned tick (Haemaphysalis longicornis) (Neumann; Acari: Ixodidae) in the northeastern United States, and in other regions where it has invaded, are still unknown, although based on studies in its native range, it is likely to be found in grasslands and open-canopy habitats.

First Record of Established Populations of the Invasive Pathogen Vector and Ectoparasite Haemaphysalis longicornis (Acari: Ixodidae) in Connecticut, United States

A number of invasive tick species capable of transmitting pathogens have been accidentally introduced into the U.S. in recent years. The invasion and further range expansion of these exotic ticks have been greatly facilitated by frequent global travel and trade as well as increases in legal and illegal importation of animals. We describe the discovery of the first established populations of Haemaphysalis longicornis Neumann and the first fully engorged human parasitizing specimen documented through passive tick surveillance in Fairfield County, Connecticut, U.S. We also report several individual specimens of this invasive arthropod and vector of multiple pathogens of medical and veterinary importance collected through active tick surveillance from three counties (Fairfield, New Haven, and New London). Considering the potential for invasive ticks to transmit numerous native and emerging pathogens, the implementation of comprehensive surveillance programs will aid in prompt interception of these ticks and reduce the risk of infection in humans and wildlife.

Highlights of Medical Entomology, 2020

Medical Entomology as a field is inherently global - thriving on international and interdisciplinary collaborations and affected dramatically by arthropod and pathogen invasions and introductions. This past year also will be remembered as the year in which the SARS-CoV-2 COVID-19 pandemic affected every part of our lives and professional activities and impacted (or changed, sometimes in good ways) our ability to collaborate and detect or respond to invasions. This incredible year is the backdrop for the 2020 Highlights in Medical Entomology. This article highlights the broad scope of approaches and disciplines represented in the 2020 published literature, ranging from sensory and chemical ecology, population genetics, impacts of human-mediated environmental change on vector ecology, life history and the evolution of vector behaviors, to the latest developments in vector surveillance and control.

Data from expressed sequence tags from the organs and embryos of parthenogenetic Haemaphysalis longicornis

Objectives

Haemaphysalis longicornis is the most important tick species in Japan and has a wide range of vector capacity. Due to its veterinary and medical importance, this tick species has been used as a model for tick/vector biological studies. To identify the key molecules associated with physiological processes during blood feeding and embryogenesis, full-length cDNA libraries were constructed using the fat body, hemocytes-containing hemolymph, midgut, ovary and salivary glands of fed females and embryos of the laboratory colony of parthenogenetic H. longicornis. The sequences of cDNA from the salivary glands had been already released. However, the related information is still poor, and the other expressed sequence tags have not yet been deposited.

Data description

A total of 39,113 expressed sequence tags were obtained and deposited at the DNA DataBank of Japan. There were 7745 sequences from embryos, 7385 from the fat body, 8303 from the hemolymph including hemocytes, 7385 from the midgut, and 8295 from the ovary. The data, including expressed sequence tags from the salivary glands was summarized into Microsoft Excel files. Sharing this data resource with the tick research community will be valuable for the identification of novel genes and advance the progress of tick research.

The first detection of Anaplasma capra, an emerging zoonotic Anaplasma sp., in erythrocytes

An emerging infectious disease caused by “Anaplasma capra” was reported in a 2015 survey of 477 hospital patients with a tick-bite history in China. However, the morphological characteristics and parasitic location of this pathogen are still unclear, and the pathogen has not been officially classified as a member of the genus Anaplasma. Anaplasma capra-positive blood samples were collected, blood cells separated, and DNA of whole blood cells, erythrocytes, and leukocytes extracted. Multiplex PCR detection assay was used to detect whole blood cell, erythrocytes and leukocytes, DNA samples, and PCR identification, nucleic acid sequencing, and phylogenetic analyses based on A. capra groEL, 16S rRNA, gltA, and msp4 genes. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Wright–Giemsa staining, chromogenic in situ hybridization (CISH), immunocytochemistry, and indirect immunofluorescence assay (IFA) were used to identify the location and morphological characteristics of A. capra. Multiple gene loci results demonstrated that erythrocyte DNA samples were A. capra-positive, while leukocyte DNA samples were A. capra-negative. Phylogenetic analysis showed that A. capra is in the same clade with the A. capra sequence reported previously. SEM and TEM showed one or more pathogens internally or on the outer surface of erythrocytes. Giemsa staining, CISH, immunocytochemistry, and IFA indicated that erythrocytes were A. capra-positive. This study is the first to identify the novel zoonotic tick-borne Anaplasma sp., “Anaplasma capra,” in host erythrocytes. Based on our results, we suggest revision of Genus Anaplasma and formally name “A. capra” as Anaplasma capra sp. nov.

Rapid Discovery and Detection of Haemaphysalis longicornis through the Use of Passive Surveillance and Collaboration: Building a State Tick-Surveillance Network

Between March 2019 and February 2020, Asian long-horned ticks (Haemaphysalis longicornis Neumann, 1901) were discovered and collected for the first time in one middle and seven eastern Tennessee counties, facilitated by a newly developed passive and collaborative tick-surveillance network. Network collaborators included federal, state, county, university, and private resource personnel working with companion animals, livestock, and wildlife. Specimens were collected primarily from dogs and cattle, with initial detections of female adult stage ticks by stakeholders associated with parasitology positions (e.g., entomologists and veterinary parasitologists). Initial county tick detections were confirmed with morphological and molecular identifications, and then screened for the presence of animal-associated pathogens (Anaplasma marginale, Babesia species, Ehrlichia species, and Theileria orientalis), for which all tests were negative. Herein, we describe the identification and confirmation of these tick specimens as well as other results of the surveillance collaboration.

Complete mitochondrial genome of Asian longhorned tick, Haemaphysalis longicornis, Neumann, 1901 (Acari: Ixodida: Ixodidae) identified in the United States

Haemaphysalis longicornis (Ixodida: Ixodidae), the Asian longhorned tick, which is native to temperate East Asia, has been recently detected in the northeastern region of the United States, drawing concerns about its potential impact on the US animal and public health sectors. Knowledge about the genetic features of H. longicornis found in the US is limited. Therefore, we sequenced the complete mitochondrial genome (mt-genome) from two H. longicornis ticks recently collected in the State of New York, USA, in 2020. These ticks were morphologically identified and tested for tick-borne pathogens at the Connecticut Veterinary Medical Diagnostic Laboratory (Storrs, CT). The mt-genome was 14,694 bp in length and encoded 37 genes, including 13 protein-coding genes, 22 transfer RNAs, and two ribosomal RNAs. Phylogenetic analysis showed that the mt-genome clustered with those of other H. longicornis identified in China. The mt-genome sequence was 99.7% identical to a H. longicornis mt-genome (GenBank: MK439888) collected in China. The cox1 gene haplotype in these ticks belonged to the H1 type, which is the dominant haplotype present in central NJ and Staten Island, NY. The complete mt-genome data are needed to provide insights into genetic changes and phylogenetic studies of H. longicornis ticks.

A multi-seasonal study investigating the phenology, host and habitat associations, and pathogens of Haemaphysalis longicornis in Virginia, U.S.A

Understanding the abiotic and biotic variables affecting tick populations is essential for studying the biology and health risks associated with vector species. We conducted a study on the phenology of exotic Haemaphysalis longicornis (Asian longhorned tick) at a site in Albemarle County, Virginia, United States. We also assessed the importance of wildlife hosts, habitats, and microclimate variables such as temperature, relative humidity, and wind speed on this exotic tick's presence and abundance. In addition, we determined the prevalence of infection with selected tick-borne pathogens in host-seeking H. longicornis. We determined that the seasonal activity of H. longicornis in Virginia was slightly different from previous studies in the northeastern United States. We observed nymphal ticks persist year-round but were most active in the spring, followed by a peak in adult activity in the summer and larval activity in the fall. We also observed a lower probability of collecting host-seeking H. longicornis in field habitats and the summer months. In addition, we detected H. longicornis on several wildlife hosts, including coyote (Canis latrans), eastern cottontail (Sylvilagus floridanus), raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), white-tailed deer (Odocoileus virginianus), woodchuck (Marmota monax), and a Peromyscus sp. mouse. This latter record is the first detection of a larval H. longicornis on a North American rodent host important to the enzootic maintenance of tick-borne pathogens of humans and animals. Finally, we continued to detect the exotic piroplasm parasite, Theileria orientalis Ikeda, in H. longicornis as well as other pathogens, including Rickettsia felis, Anaplasma phagocytophilum (AP-1), and a Hepatozoon sp. previously characterized in Amblyomma americanum. These represent some of the first detections of arthropod-borne pathogens native to the United States in host-seeking H. longicornis. These data increase our understanding of H. longicornis biology in the United States and provide valuable information into the future health risks associated with this tick and pathogens.