Prevalence of Severe Fever with Thrombocytopenia Syndrome Virus in Ticks Collected from National Parks in Korea

Molecular detection of Borrelia theileri in cattle in Korea

Bovine borreliosis, caused by Borrelia theileri which is transmitted via hard tick bites, is associated with mild clinical symptoms, such as fever, lethargy, hemoglobinuria, anorexia, and anemia. Borrelia theileri infects various animals, such as cattle, deer, horses, goats, sheep, and wild ruminants, in Africa, Australia, and South America. Notably, no case of B. theileri infection has been reported in Korean cattle to date. In this study, 101 blood samples were collected from a Korean indigenous cattle breed, among which 1.98% tested positive for B. theileri via nested PCR. The obtained sequences exhibited high homology with B. theileri strains identified in other regions. Phylogenetic analysis of 16S rRNA confirmed the B. theileri group affiliation; however, flagellin B sequences exhibited divergence, potentially due to regional evolutionary differences. This study provides the first molecular confirmation of B. theileri infection in Korean livestock. Further isolation and nucleotide sequence analyses are necessary to better understand the presence of B. theileri strains in cows in Korea.

Human Tick-Borne Diseases and Advances in Anti-Tick Vaccine Approaches: A Comprehensive Review

This comprehensive review explores the field of anti-tick vaccines, addressing their significance in combating tick-borne diseases of public health concern. The main objectives are to provide a brief epidemiology of diseases affecting humans and a thorough understanding of tick biology, traditional tick control methods, the development and mechanisms of anti-tick vaccines, their efficacy in field applications, associated challenges, and future prospects. Tick-borne diseases (TBDs) pose a significant and escalating threat to global health and the livestock industries due to the widespread distribution of ticks and the multitude of pathogens they transmit. Traditional tick control methods, such as acaricides and repellents, have limitations, including environmental concerns and the emergence of tick resistance. Anti-tick vaccines offer a promising alternative by targeting specific tick proteins crucial for feeding and pathogen transmission. Developing vaccines with antigens based on these essential proteins is likely to disrupt these processes. Indeed, anti-tick vaccines have shown efficacy in laboratory and field trials successfully implemented in livestock, reducing the prevalence of TBDs. However, some challenges still remain, including vaccine efficacy on different hosts, polymorphisms in ticks of the same species, and the economic considerations of adopting large-scale vaccine strategies. Emerging technologies and approaches hold promise for improving anti-tick vaccine development and expanding their impact on public health and agriculture.

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

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

Research Progress of Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is a new infectious disease first discovered in Ta-pieh Mountains in central China in 2009. It is caused by a novel bunyavirus infection (SFTSV). Since the first discovery of SFTSV, there have been case reports and epidemiological studies on SFTS in several East Asian countries, such as South Korea, Japan, Vietnam and so on. With the rising incidence of SFTS and the rapid spread of the novel bunyavirus around the world, it is clear that the virus has a pandemic potential and may pose a threat to global public health in the future. Early studies have suggested that ticks are an important medium for the transmission of SFTSV to humans; in recent years, it has been reported that there is also human-to-human transmission. In endemic areas, potential hosts include a variety of livestock and wildlife. When people are infected with SFTV, the main clinical manifestations are high fever, thrombocytopenia, leukocytopenia, gastrointestinal symptoms, liver and kidney function damage, and even MODS, with a mortality rate of about 10-30%. This article reviews the latest progress of novel bunyavirus, including virus transmission vector, virus genotypic diversity and epidemiology, pathogenesis, clinical manifestation and treatment.

Haemaphysalis flava ticks as a competent vector of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome virus (SFTSV), a tick-borne Bunyavirus, causes an emerging hemorrhagic fever in humans with a high fatality in Asia. The tick vectors and hosts of SFTSV are not well studied. We evaluated SFTSV transmission in laboratory reared Haemaphysalis flava ticks. RT-PCR demonstrated that after acquisition feeding in SFTSV-infected rabbits, 10 % (4/40) engorged larvae, 25% (5/20) engorged nymphs, and 50% (5/10) engorged females of H. flava became SFTSV RNA positive; after engorged larvae and nymphs molted into nymphs and adults, respectively, 12.5% (3/24) newly molted nymphs and 20% (2/10) newly molted adults were SFTSV RNA positive. Among 30 engorged females that oviposited, 10% (3/30) clutches of eggs and 3.3% (1/30) colonies of larvae were RNA positive for SFTSV. RT-PCR also showed that 6 days after being infested with SFTSV-infected ticks, 100% (3/3) rabbits infested with larvae, 100% (2/2) rabbits infested with nymphs, and 100% (2/2) rabbits infested with adult ticks became SFTSV RNA positive. In conclusion, H. flava can acquire SFTSV from infected rabbits by feeding; there is transstadial and transovarial transmission of the virus and all three stages of H. flava can transmit SFTSV to rabbits by feeding. Thus, H. flava tick is an effective vector of SFTSV and may play a role in the transmission of SFTSV in wild animals and humans.

Whole-genome sequencing and genetic diversity of severe fever with thrombocytopenia syndrome virus using multiplex PCR-based nanopore sequencing, Republic of Korea

Background

Whole-genome sequencing plays a critical role in the genomic epidemiology intended to improve understanding the spread of emerging viruses. Dabie bandavirus, causing severe fever with thrombocytopenia syndrome (SFTS), is a zoonotic tick-borne virus that poses a significant public health threat. We aimed to evaluate a novel amplicon-based nanopore sequencing tool to obtain whole-genome sequences of Dabie bandavirus, also known as SFTS virus (SFTSV), and investigate the molecular prevalence in wild ticks, Republic of Korea (ROK).

Principal findings

A total of 6,593 ticks were collected from Gyeonggi and Gangwon Provinces, ROK in 2019 and 2020. Quantitative polymerase chain reaction revealed the presence of SFSTV RNA in three Haemaphysalis longicornis ticks. Two SFTSV strains were isolated from H. longicornis captured from Pocheon and Cheorwon. Multiplex polymerase chain reaction-based nanopore sequencing provided nearly full-length tripartite genome sequences of SFTSV within one hour running. Phylogenetic and reassortment analyses were performed to infer evolutionary relationships among SFTSVs. Phylogenetic analysis grouped SFTSV Hl19-31-4 and Hl19-31-13 from Pocheon with sub-genotype B-1 in all segments. SFTSV Hl20-8 was found to be a genomic organization compatible with B-1 (for L segment) and B-2 (for M and S segments) sub-genotypes, indicating a natural reassortment between sub-genotypes.

Conclusion/Significance

Amplicon-based next-generation sequencing is a robust tool for whole-genome sequencing of SFTSV using the nanopore platform. The molecular prevalence and geographical distribution of SFTSV enhanced the phylogeographic map at high resolution for sophisticated prevention of emerging SFTS in endemic areas. Our findings provide important insights into the rapid whole-genome sequencing and genetic diversity for the genome-based diagnosis of SFTSV in the endemic outbreak.

SFTSV infection in rodents and their ectoparasitic chiggers

SFTSV, a tick-borne bunyavirus causing a severe hemorrhagic fever termed as severe fever with thrombocytopenia syndrome (SFTS). To evaluate the potential role of rodents and its ectoparasitic chiggers in the transmission of SFTSV, we collected wild rodents and chiggers on their bodies from a rural area in Qingdao City, Shandong Province, China in September 2020. PCR amplification of the M and L segments of SFTSV showed that 32.3% (10/31) of rodents and 0.2% (1/564) of chiggers (Leptotrombidium deliense) from the rodents were positive to SFTSV. Our results suggested that rodents and chiggers may play an important role in the transmission of SFTSV, although the efficiency of chiggers to transmit SFTSV needs to be further investigated experimentally.

Molecular Detection of Anaplasma phagocytophilum and Ehrlichia Species in Ticks Removed from Humans in the Republic of Korea

Human granulocytic anaplasmosis (HGA) and human monocytic ehrlichiosis (HME) are zoonotic tick-borne diseases transmitted via tick bites. To determine the state of human Anaplasma and Ehrlichia infections caused by tick bites in the Republic of Korea (ROK), we conducted a nationwide investigation of human cases of tick bites in 2020. A total of 180 ticks were obtained, comprising Haemaphysalis longicornis (70.0%), Amblyomma testudinarium (17.8%), Ixodes nipponensis (6.1%), H. flava (4.4%), and I. persulcatus (1.7%). In three cases (1.7%; 95% CI: 0.3-4.9), A. phagocytophilum was detected in Ixodes ticks using primers for Anaplasma-specific genes (16s rRNA, ankA, and msp4). Conversely, Ehrlichia sp. was only detected in H. longicornis, in two cases (1.1%; 95% CI: 0.1-4.0). To the best of our knowledge, this is the first record of Ehrlichia sp. in ticks parasitizing humans in the ROK. As concerns remain about the possibility of HGA and HME transmission, continuous monitoring and management of the pathogens and vectors are necessary.

Severe Fever with Thrombocytopenia Syndrome Virus in Ticks in the Republic of Korea

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a zoonotic, tick-borne RNA virus of the genus Bandavirus (Family Phenuiviridae), mainly reported in China, Japan, and the Republic of Korea (Korea). For the purpose of this study, a total of 3,898 adult and nymphal ticks of species Haemaphysalis longicornis (94.2%), Haemaphysalis flava (5.0%), Ixodes nipponensis (0.8%), and 1 specimen of Ixodes ovatus, were collected from the Deogyusan National Park, Korea, between April 2016 and June 2018. A single-step reverse transcriptase–nested PCR was performed, targeting the S segment of the SFTSV RNA. Total infection rate (IR) of SFTSV in individual ticks was found to be 6.0%. Based on developmental stages, IR was 5.3% in adults and 6.0% in nymphs. The S segment sequences obtained from PCR were divided into 17 haplotypes. All haplotypes were phylogenetically clustered into clades B-2 and B-3, with 92.7% sequences in B-2 and 7.3% in B-3. These observations indicate that the Korean SFTSV strains were closer to the Japanese than the Chinese strains. Further epidemiological studies are necessary to better understand the characteristics of the Korean SFTSV and its transmission cycle in the ecosystem.

Serological evidence of Anaplasma spp., Borrelia burgdorferi and Ehrlichia canis in dogs from the Republic of Korea by rapid diagnostic test kits

Background

Emergent and re-emergent canine tick-borne infections are attracting increasing attention worldwide. The rise in pet ownership and the close relationship between dogs and their owners are the most concerning factors because dogs may act as competent reservoirs for human tick-transmitted infectious agents.

Objectives

This study contributes to the epidemiological surveillance of canine tick-transmitted infections with zoonotic risk in the Republic of Korea (ROK) by investigating the seroprevalence of the pathogens, Anaplasma spp., Borrelia burgdorferi, and Ehrlichia canis.

Methods

Four hundred and thirty whole blood samples from domestic dogs were collected in seven metropolitan cities and nine provinces in the ROK and tested using SensPERT Ab test kits (VetAll Laboratories®) to detect seroreactive animals.

Results

The seroprevalence rates identified were 9.8% (42/430) for Anaplasma spp., 2.8% (12/430) for B. burgdorferi, and 1.4% (6/430) for E. canis. The risk factors evaluated in this study that could be associated with the development of a humoral immune response, such as sex, age, and history of tick exposure, were similar. There was only one exception for dogs seroreactive to Anaplasma spp., where the risk factor “tick exposure” was statistically significant (p = 0.047).

Conclusions

This serological survey exhibited the widespread presence of Anaplasma spp., B. burgdorferi, and E. canis throughout the ROK. Hence, dogs may play a key role as the sentinel animals of multiple zoonotic infectious agents in the country.

Cloning, expression, and function of ferritins in the tick Haemaphysalis flava

The full-length cDNA of two ferritins of Haemaphysalis flava were cloned after which recombinant Hf-FER1 and Hf-FER2 were expressed and their function was analyzed. In addition, RNA interference (RNAi) based on the injection of Hf-fer1 or Hf-fer2 dsRNA into fully engorged female ticks was performed. The cDNA encoding Hf-FER1 is 834 bp in length. It contains an iron-responsive element in the 5' untranslated region and encodes 174 amino acid residues. The full-length cDNA of Hf-FER2 contains 696 bp and encodes 199 amino acids, including a putative signal peptide sequence. Hf-FER1 and Hf-FER2 both have the ferroxidase iron center and the ferrihydrite nucleation center. The evolutionary relationship of Hf-FER1 and Hf-FER2 was established, and the predicted quaternary structures were assembled as typical spherical shells composed of 24 subunits which was demonstrated by nature PAGE. Real-time PCR showed that Hf-fer1 and Hf-fer2 were expressed in all developmental stages, with the highest expression in fully engorged females. The expression of Hf-fer1 and Hf-fer2 were relatively high in unfed larvae. Hf-fer1 was expressed in all tissues and was especially abundant in the salivary glands of fully engorged females. In contrast, the highest levels of Hf-fer2 were found in the midgut of fully engorged females, and no expression was found in the salivary glands of this life stage. Both recombinant Hf-FER1 and Hf-FER2 had iron-binding capabilities. Silencing of both Hf-fer1 and Hf-fer2 affected fecundity. Compared to the control, the percentage of ticks that laid eggs in the Hf-fer1 and Hf-fer2 RNAi groups was 73.3% and 66.7%, respectively. The silenced ticks that laid eggs had lower egg weight to body weight ratios, and the eggs had abnormal morphologies. The hatchability of eggs with normal morphology in the Hf-fer1 and Hf-fer2 silenced groups was 47.8% and 22.8%, respectively, which was significantly different from the control group (P < 0.005). These findings indicate that Hf-FER1 and Hf-FER2 play important roles in the iron storage of H. flava.

Vectors, Hosts, and the Possible Risk Factors Associated with Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is a disease caused by infection with the SFTS virus (SFTSV). SFTS has become a crucial public health concern because of the heavy burden, lack of vaccines, effective therapies, and high-fatality rate. Evidence suggests that SFTSV circulates between ticks and animals in nature and is transmitted to humans by tick bites. In particular, ticks have been implicated as vectors of SFTSV, where domestic or wild animals may play as the amplifying hosts. Many studies have identified antigens and antibodies against SFTSV in various animals such as sheep, goats, cattle, and rodents. Besides, person-to-person transmission through contact with blood or mucous of an infected person has also been reported. In this study, we reviewed the literature and summarized the vectors and hosts associated with SFTS and the possible risk factors.

Seroepidemiologic survey of emerging vector-borne infections in South Korean forest/field workers

With global warming and lush forest change, vector-borne infections are expected to increase in the number and diversity of agents. Since the first report of severe fever with thrombocytopenia syndrome (SFTS) in 2013, the number of reported cases has increased annually in South Korea. However, although tick-borne encephalitis virus (TBEV) was detected from ticks and wild rodents, there is no human TBE case report in South Korea. This study aimed to determine the seroprevalence of TBEV and SFTS virus (SFTSV) among forest and field workers in South Korea. From January 2017 to August 2018, a total 583 sera were obtained from the forest and field workers in South Korea. IgG enzyme-linked immunosorbent assay (ELISA) and neutralization assay were conducted for TBEV, and indirect immunofluorescence assay (IFA) and neutralization assay were performed for SFTSV. Seroprevalence of TBEV was 0.9% (5/583) by IgG ELISA, and 0.3% (2/583) by neutralization assay. Neutralizing antibody against TBEV was detected in a forest worker in Jeju (1:113) and Hongcheon (1:10). Only 1 (0.2%) forest worker in Yeongju was seropositive for SFTSV by IFA (1:2,048) and neutralizing antibody was detected also. In conclusion, this study shows that it is necessary to raise the awareness of physicians about TBEV infection and to make efforts to survey and diagnose vector-borne diseases in South Korea.

Characterization of AV422 from Haemaphysalis flava ticks in vitro

Ticks are hematophagous ectoparasites and cause a major public health threat worldwide. Development of anti-tick vaccines is regarded to be an optimal alternative for tick control. AV422, a unique protein in ticks, is secreted into hosts during blood-feeding, but its roles are not confirmed in Haemaphysalis flava ticks. We retrieved a gene fragment encoding AV422 from a transcriptome dataset of H. flava, and based on it, we reconstructed the full length of AV422 from H. flava (Hf-AV422) by rapid amplification of cDNA ends. Expression profiles of Hf-AV422 in whole ticks and organs of different engorgement levels were determined by qPCR. Then its opening reading frame (ORF) was expressed in Escherichia coli strain BL21 (DE3). The prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) assays were conducted to test anticoagulant activities of the purified recombinant protein (rHf-AV422). The full length of AV422 was 1152 bp. Hf-AV422 showed to be conserved as indicated by multiple sequence alignment. Expression of Hf-AV422 was significantly higher in salivary glands and cuticles than in ovaries. Its expression in whole ticks decreased during engorgement with the highest levels in 1/4 engorged ticks. rHf-AV422 prolonged PT, APTT and TT when incubated with rabbit plasma. Our data demonstrated that Hf-AV422 is a conserved salivary protein with anticoagulant activity. Further studies are needed to test in detail its functional properties to ensure it an adequate antigen candidate for the development of broad-spectrum vaccines against ticks.

Nationwide Temporal and Geographical Distribution of Tick Populations and Phylogenetic Analysis of Severe Fever with Thrombocytopenia Syndrome Virus in Ticks in Korea, 2020

Since 2010, the Korea Disease Control and Prevention Agency has established centers at 16 locations to monitor disease vectors and pathogens. Here, we examined tick populations to understand the geographical and temporal distribution of severe fever with thrombocytopenia syndrome virus (SFTSV) vectors in 2020. From April to November, 63,376 ticks were collected from traps to monitor tick populations, with a trap index of 41.3. Tick incidence varied from April to October, with population peaks observed for nymphs in May, adults in July, and larvae in September. The predominant tick species were Haemaphysalis longicornis, Haemaphysalis spp., H. flava, Ixodes spp., Amblyomma testudinarium, and Ixodes nipponensis. Approximately 50% of the collected ticks were pooled into 2973 groups to detect the rate of SFTSV infection in ticks. The minimum infection rate (MIR) of SFTSV was 0.2%, and Andong had the highest MIR for SFTSV (4.0%). The B3 genotype was the most prevalent (52.2%) followed by B2 (28.6%), B5 (15.9%), B4 (1.6%), and B6 (1.6%). We identified widely distributed tick species and a high degree of diversity in SFTSV strains in ticks from different geographical regions. The results may provide a basis for future epidemiological studies and risk assessments for tick-borne diseases.

Significance of peripheral blood indexes in differential diagnoses of SARS-CoV-2 and New Bunia virus

We aimed to provide a laboratory basis for differential diagnosis of COVID-19 and severe fever with thrombocytopenia syndrome (SFTS). Clinical data were collected from 32 COVID-19 patients (2019-nCoV group), 31 SFTS patients (SFTS group) and 30 healthy controls (control group). For each group of hospitalized patients, a retrospective analysis was performed on specific indices, including cytokines, T-lymphocyte subsets, routine blood parameters, C-reactive protein (CRP) and procalcitonin (PCT), and receiver operating characteristic (ROC) curves for the indices revealed the differences among groups. Compared with the 2019-nCoV group, the SFTS group had a significantly and greatly decreased counts of WBC, absolute lymphocyte, PLT and absolute CD4⁺ T lymphocyte (P < 0.05); the IL-6, TNF-α, D-D and PCT levels of the SFTS group were higher than those of the 2019-nCoV group (P < 0.05). Compared with those of the SFTS group, the CRP and FIB levels of the 2019-nCoV group were greatly increased (P < 0.05). The ROC curves showed that area under the curves (AUCs) for FIB, PLT and TNF-α were greater than 0.85, demonstrating high diagnostic value. At the initial stage of SARS-CoV-2 or SFTS virus infection, PLT, FIB and TNF-α have definitive clinical value for the early and differential diagnosis of these two infections.

Hard Ticks as Vectors Tested Negative for Severe Fever with Thrombocytopenia Syndrome in Ganghwa-do, Korea during 2019-2020

This study aimed to characterize the seasonal abundance of hard ticks that transmit severe fever with thrombocytopenia syndrome virus from April to November 2019 and 2020 on Ganghwa-do, Incheon Metropolitan City, Korea. The ticks were collected at grassland, grave site, copse and mountain road using a collection trap method. The ixodid hard ticks comprising three species (Haemaphysalis longicornis, H. flava, and Ixodes nipponensis) collected were 6,622 in 2019 and 3,811 in 2020. H. longicornis was the most frequent (97.9% in 2019 and 96.0% in 2020), followed by H. flava (2.0% and 3.0% in 2019 and 2020, respectively) and I. nipponensis (less than 0.1%). Our study demonstrated that seasonal patterns of the tick populations examined for two years were totally unsimilar. The hard ticks tested using RT-qPCR were all negative for severe fever with thrombocytopenia syndrome virus.

Severe fever with thrombocytopenia syndrome virus: emerging novel phlebovirus and their control strategy

An emerging infectious disease first identified in central China in 2009, severe fever with thrombocytopenia syndrome (SFTS) was found to be caused by a novel phlebovirus. Since SFTSV was first identified, epidemics have occurred in several East Asian countries. With the escalating incidence of SFTS and the rapid, worldwide spread of SFTSV vector, it is clear this virus has pandemic potential and presents an impending global public health threat. In this review, we concisely summarize the latest findings regarding SFTSV, including vector and virus transmission, genotype diversity and epidemiology, probable pathogenic mechanism, and clinical presentation of human SFTS. Ticks most likely transmit SFTSV to animals including humans; however, human-to-human transmission has been reported. The majority of arbovirus transmission cycle includes vertebrate hosts, and potential reservoirs include a variety of both domestic and wild animals. Reports of the seroprevalence of SFTSV in both wild and domestic animals raises the probability that domestic animals act as amplifying hosts for the virus. Major clinical manifestation of human SFTS infection is high fever, thrombocytopenia, leukocytopenia, gastrointestinal symptoms, and a high case-fatality rate. Several animal models were developed to further understand the pathogenesis of the virus and aid in the discovery of therapeutics and preventive measures.

Invasive pulmonary aspergillosis is a frequent complication in patients with severe fever with thrombocytopenia syndrome: A retrospective study

OBJECTIVES

Invasive pulmonary aspergillosis (IPA) usually occurs in immunocompromised hosts. It has recently been reported that patients with severe fever with thrombocytopenia syndrome (SFTS) can also develop IPA. The aim of this study was to determine the incidence of IPA in SFTS patients and to investigate the relevant clinical, imaging, and laboratory characteristics.

METHODS

A retrospective review was conducted of all patients with SFTS admitted to Nanjing Drum Tower Hospital, a tertiary hospital in Nanjing City, China, between January 2016 and December 2019. The patients were divided into two groups according to whether they had IPA: the IPA group and the non-IPA group. Data on clinical manifestations, laboratory findings, imaging characteristics, treatments, and outcomes were collected and analysed.

RESULTS

A total of 91 SFTS patients were included, of whom 29 (31.9%) developed IPA. In-hospital mortality (22.0%) was higher in the IPA group than in the non-IPA group. Univariate logistic regression showed that diabetes, cough, wheezing, amylase level, vasopressor use, encephalopathy, and intensive care unit transfer were risk factors for the development of IPA. Multivariate logistic regression analysis identified wheezing as an independent predictor of IPA in SFTS patients.

CONCLUSIONS

SFTS combined with IPA is associated with high morbidity and mortality. It is necessary to strengthen screening for fungal infections after admission in SFTS patients. However, whether early antifungal prophylaxis should be administered needs further investigation.

Detection of Multiple Intracellular Bacterial Pathogens in Haemaphysalis flava Ticks Collected from Hedgehogs in Central China

Tickborne intracellular bacterial pathogens including Anaplasma, Coxiella burnetti, Ehrlichia, and Rickettsia cause emerging infectious diseases worldwide. PCR was used to amplify the genes of these pathogens in Haemaphysalis flava ticks collected from hedgehogs in Central China. Among 125 samples including 20 egg batches, 24 engorged females, and 81 molted male and female adult ticks, the DNA sequences and phylogenetic analysis showed that the minimum infection rate of the ticks was 4% (5/125) for A. bovis, 3.2% (4/125) for C. burnetti, 9.6%, (12/125) for E. ewingii, and 5.6% for Rickettsia including R.japonica (3.2%, 4/125) and R. raoultii (2.4%, 3/125), respectively. The prevalence of these pathogens was significantly higher in dead engorged females (83.3%, 20/24) than in eggs (5%, 1/20) and molted ticks (8.6%, 7/81). Our study indicated that H. flava ticks could be infected with multiple species of tickborne pathogens including Anaplasma, C. burnetti, Ehrlichia, and Rickettsia in Central China, and the prevalence of these pathogens was reduced during transovarial and transstadial transmission in ticks, suggesting that ticks may not be real reservoirs but only vectors for these tickborne pathogens.

A life stage-targeted acaricide application approach for the control of Haemaphysalis longicornis

Haemaphysalis longicornis Neumann is an invasive tick species that has recently been detected in the eastern United States. We designed field studies to monitor the population dynamics of H. longicornis over a year (2019) in New Jersey, and to assess the efficacy of a pyrethroid acaricide (lambda-cyhalothrin) in controlling this tick using a stage-treatment approach. Nymphs were the most abundant life stage found host-seeking from May through early July, followed by a brief period of high adult activity in mid-July, and a very high larval peak extending from late July through October. Overall, 542 adults, 1910 nymphs, and 69,238 larvae were recorded during the sampling. In the present study, the efficacy of acaricide treatments to suppress host-seeking ticks was assessed by applying lambda-cyhalothrin once during each of the three periods of activity for nymphs (June), adults (July), and larvae (August), or sequentially during all three months. Control plots were left untreated and used for phenology studies. Applications in June and July provided 100 % control of all life stages, including the dominant nymphal and adult stages for 42 and 35 d, respectively. Ticks re-established at normal or reduced levels following applications in June or July, respectively, compared to untreated controls. The application in August provided 100 % control for 49 d, and a high level of suppression (>99 % control) remained through the end of the tick season in October. This study therefore supports that single pyrethroid applications can provide 100 % control of H. longicornis for up to 7 wk, and a single late-summer application towards the end of host-seeking adult activity can provide near complete control of the larval population. An evaluation of single applications over the course of the season revealed that treatments in July or August did not lead to significant reductions in the nymphal population. However, multiple sequential treatments targeting all life stages provided 66 %, 97 %, and >99 % control of adults, nymphs, and larvae, respectively through the season of H. longicornis activity.

Role of three tick species in the maintenance and transmission of Severe Fever with Thrombocytopenia Syndrome Virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel phlebovirus in the Bunyaviridae family, causing SFTS with high mortality rate. Haemaphysalis longicornis ticks has been demonstrated as a competent vector of SFTSV by experimental transmission study and field study. However, there has been query whether other tick species that infest human beings in the SFTS endemic regions are capable of transmitting the pathogen. Here by performing experimental transmission study, we compared the capable of transmitting SFTSV among Ixodes sinensis, Ixodes persulcatus and Dermacentor silvarum ticks. The transovarial transmission was seen in the I. sinensis ticks with a rate of 40%, but neither in I. persulcatus nor in D. silvarum ticks. I. sinensis ticks also have the ability to transmit SFTSV horizontally to uninfected mice at 7 days after feeding, but not for I. persalcatus or D. silvarum ticks. In the transstadial transmission of I. persulcatus and D. silvarum ticks, I. persulcatus ticks were tested negative from larvae to adults. But the D. silvarum ticks were tested positive from larvae to nymphs, with the positive rate of 100% (10/10) for engorged larval ticks and 81.25% (13/16) for molted nymphs. However, the mice bitten by SFTSV-infected D. silvarum nymphs were negative for SFTSV detection. Therefore, there is not enough evidence to prove the transstadial transmission of SFTSV in I. persalcatus and D. silvarum ticks.

Due to its wide distribution and high fatality rate (16%-30%), severe fever with thrombocytopenia syndrome (SFTS) has been listed in the top 10 priority diseases blueprint by the world health organization (WHO) in 2017. SFTSV is a novel phlebovirus in the Bunyaviridae family, and Haemaphysalis longicornis tick has been demonstrated as a competent vector of SFTSV by experimental transmission study and field study. However, there are many other tick species that infest human beings in the SFTS endemic regions. Therefore, it’s neccessary to query whether these tick species are capable of transmitting SFTSV. The authors found that in addition to H. longicornis ticks, Ixodes sinensis ticks also served as an efficient vector capable of transovarial transmitting SFTSV, therefore posing as a potential threat in causing the circulation of SFTSV. In contrast, Dermacentor silvarum and Ixodes persulcatus ticks might not serve as an efficient vector of transmitting SFTSV. This research will provide important reference for the surveillance of SFTSV and the disease prevention and control.

Scalp eschar and neck lymphadenopathy after tick bite (SENLAT) caused by Bartonella henselae in Korea: a case report

Background

Tick-borne lymphadenopathy (TIBOLA) is an infectious disease, mainly caused by species from the spotted fever group rickettsiae and is characterized by enlarged lymph nodes following a tick bite. Among cases of TIBOLA, a case of scalp eschar and neck lymphadenopathy after tick bite (SENLAT) is diagnosed when an eschar is present on the scalp, accompanied by peripheral lymphadenopathy (LAP). Only a few cases of SENLAT caused by Bartonella henselae have been reported.

Case presentation

A 58-year-old male sought medical advice while suffering from high fever and diarrhea. Three weeks before the visit, he had been hunting a water deer, and upon bringing the deer home discovered a tick on his scalp area. Symptoms occurred one week after hunting, and a lump was palpated on the right neck area 6 days after the onset of symptoms. Physical examination upon presentation confirmed an eschar-like lesion on the right scalp area, and cervical palpation revealed that the lymph nodes on the right side were non-painful and enlarged at 2.5 × 1.5 cm. Fine needle aspiration of the enlarged lymph nodes was performed, and results of nested PCR for the Bartonella internal transcribed spacer (ITS) confirmed B. henselae as the causative agent.

Conclusion

With an isolated case of SENLAT and a confirmation of B. henselae in Korea, it is pertinent to raise awareness to physicians in other Asian countries that B. henselae could be a causative agent for SENLAT.

Severe Fever with Thrombocytopenia Syndrome Associated with Manual De-Ticking of Domestic Dogs

Background: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease. SFTS is caused by the SFTS virus, a novel phlebovirus, and is spread by ticks. Methods: A 50-year-old man was admitted to our hospital with the chief complaint of fever and was diagnosed with confirmed SFTS. An epidemiological investigation was conducted, and immunofluorescent antibody assays (IFAs) were performed to determine the role of the patient's three dogs in the transmission. PCR assays were performed using ticks that were collected with the dragging and flagging method from the patient's dogs and home. Results: PCR results were positive, and IFA confirmed an increased antibody titer. Although the reverse transcription PCR results of the three dogs were negative for SFTS virus, one dog had an elevated SFTS IFA immunoglobulin G (IgG) titer of 1:1,024. Moreover, a number of ticks were observed in the area surrounding the dog cages. Based on the findings of the patient interview, the patient was likely to have acquired SFTS by blood splash because he removed or burst ticks from the dogs with his bare hands. Although no tick bites were reported, tick transmission could not be ruled out. Studies have shown that only one in three individuals with a diagnosis of SFTS recalls a tick bite; thus, a definite exclusion of tick transmission in this case was not possible. Conclusions: The epidemiological findings of our case suggest a possible relationship between tick infestation in domestic dogs and SFTS virus transmission to humans. However, there is no direct evidence supporting this viral transmission route. Future studies are needed to further investigate a potential route of SFTS transmission by exposure to engorged tick blood or pet dogs.

A survey of proteins in midgut contents of the tick, Haemaphysalis flava, by proteome and transcriptome analysis

Tick blood meals are stored and digested in their midguts. Blood digestion is complex, and many proteins are involved. Study of the tick-derived proteins in the midgut content may aid in the discovery of active molecules that would be useful for anti-tick vaccines. We analyzed the midgut content proteomes of partially engorged female Haemaphysalis flava, fully engorged female H. flava, and hedgehog serum using liquid chromatography tandem-mass spectrometry and label-free quantitation. In this study, high-confidence protein profiling of tick midgut content was determined. Based on the search against our in-house transcriptome database, the 28 high-confidence proteins were identified. Of these, 17 were identified as tick-derived, and the rest were of unspecified origin (proteins that could not be differentiated as host-derived or tick-derived proteins). The function of these midgut content proteins identified here may involve nutrient transportation, anti-coagulation, erythrocyte lysis, detoxification, lipid metabolism, and immunization. The presence of hemoglobin suggested that the red blood cells were lysed in the gut lumen. The midgut contents contain a large amount of fibrinogen and it has the ability to clot immediately. The midgut contained mostly host-derived proteins, and these host proteins provide rich nutrients for tick development and reproduction. However, some intracellular proteins were also identified, suggesting the possibility of shedding of the midgut epithelium and ingestion of saliva during feeding. This finding advances our understanding of the digestive mechanism and will be useful in the screening of vaccine antigens.

[Arthropod-borne viruses (arboviruses)]

"Arbovirus" is a term for a virus transmitted to mammals by hematophagous arthropods; arboviruses; replicate in both mammals and arthropods. Since the life cycle of arboviruses is highly dependent on arthropods, control of the arthropods (vectors) is generally considered important for the control of arbovirus infection. Various pathogens that cause diseases in the medical and veterinary fields are grouped into arboviruses with a history of their discoveries since the early 20th century. Furthermore, because of recent advances in sequencing technology, new arboviruses have been discovered one after another. Here we would like to overview the known arboviruses and their infections.

Four Year Surveillance of the Vector Hard Ticks for SFTS, Ganghwa-do, Republic of Korea

The seasonal abundance of hard ticks that transmit severe fever with thrombocytopenia syndrome virus was monitored with a collection trap method every April to November during 2015–2018 and with a flagging method every July and August during 2015–2018 in Ganghwa-do (island) of Incheon Metropolitan City, Republic of Korea. This monitoring was performed in a copse, a short grass field, coniferous forest and broad-leaved forest. A total of 17,457 ticks (8,277 larvae, 4,137 nymphs, 3,389 females, and 1,654 males) of the ixodid ticks comprising 3 species (Haemaphysalis longicornis, H. flava, and Ixodes nipponensis) were collected with collection traps. Of the identified ticks, H. longicornis was the most frequently collected ticks (except larval ticks) (94.26%, 8,653/9,180 ticks (nymphs and adults)), followed by H. flava (5.71%, 524/9,180) and Ix. nipponensis (less than 0.04%, 3/9,180). The ticks collected with collecting traps were pooled and assayed for the presence of SFTS virus with negative results. In addition, for monitoring the prevalence of hard ticks, a total of 7,461 ticks (5,529 larvae, 1,272 nymphs, 469 females, and 191 males) of the ixodid ticks comprising 3 species (H. longicornis, H. flava, and Ix. nipponensis) were collected with flagging method. H. longicornis was the highest collected ticks (except larval ticks) (99.53%, 1,908/1,917 ticks (nymphs and adults)), followed by H. flava (1.15%, 22/1,917).