Clinical Factors Associated with SFTS Diagnosis and Severity in Cats.

Severe fever with thrombocytopenia syndrome (SFTS) is a potentially fatal tick-borne zoonosis caused by SFTS virus (SFTSV). In addition to tick bites, animal-to-human transmission of SFTSV has been reported, but little is known about feline SFTSV infection. In this study, we analyzed data on 187 cats with suspected SFTS to identify biomarkers for SFTS diagnosis and clinical outcome. Body weight, red and white blood cell and platelet counts, and serum aspartate aminotransferase and total bilirubin levels were useful for SFTS diagnosis, whereas alanine aminotransferase, aspartate aminotransferase and serum SFTSV RNA levels were associated with clinical outcome. We developed a scoring model to predict SFTSV infection. In addition, we performed a phylogenetic analysis to reveal the relationship between disease severity and viral strain. This study provides comprehensive information on feline SFTS and could contribute to the protection of cat owners, community members, and veterinarians from the risk of cat-transmitted SFTSV infection.

Outbreak of Natural Severe Fever with Thrombocytopenia Syndrome Virus Infection in Farmed Minks, China.

We isolated severe fever with thrombocytopenia syndrome virus (SFTSV) from farmed minks in China, providing evidence of natural SFTSV infection in farmed minks. Our findings support the potential role of farmed minks in maintaining SFTSV and are helpful for the development of public health interventions to reduce human infection.

Direct transmission of severe fever with thrombocytopenia syndrome virus from farm-raised fur animals to workers in Weihai, China.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease. SFTS virus (SFTSV) is transmitted by tick bites and contact with the blood or body fluids of SFTS patients. Animal-to-human transmission of SFTS has been reported in Japan, but not in China. In this study, the possible transmission route of two patients who fed and cared for farm-raised fur animals in a mink farm was explored. METHOD: An epidemiological investigation and a genetic analysis of patients, animals and working environment were carried out. RESULTS: It was found that two patients had not been bitten by ticks and had no contact with patients infected with SFTS virus, but both of them had skinned the dying animals. 54.55% (12/22) of the farm workers were positive for SFTS virus antibody. By analyzing the large, medium and small segments sequences, the viral sequences from the two patients, animals and environments showed 99.9% homology. CONCLUSION: It is suspected that the two patients may be directly infected by farm-raised animals, and that the virus may have been transmitted by aerosols when skinning dying animals. Transmission by direct blood contacts or animal bites cannot be ignored.

Suspected Transmission of Severe Fever with Thrombocytopenia Syndrome Virus from a Cat to a Veterinarian by a Single Contact: A Case Report.

A 67-year-old male veterinarian presented with fatigue, anorexia, and diarrhea. Although there were no tick bite marks, we suspected severe fever with thrombocytopenia syndrome (SFTS) due to bicytopenia, mild disturbance of consciousness, and a history of outdoor activities. Thus, we started immunoglobulin therapy immediately. A serum reverse transcription-polymerase chain reaction (RT-PCR) test for SFTS virus (SFTSV) was positive. The patient had treated a cat with thrombocytopenia 10 days prior to admission. The cat's serum SFTSV RT-PCR test result was positive, and the whole genome sequences of the patient's and cat's SFTSV were identical, suggesting the possibility of transmission from the cat to the patient. Other cases of direct cat-to-human SFTV transmission have been reported recently. Mucous membranes should be protected, including eye protection, in addition to standard precautions, when in contact with any cat with suspected SFTS.

Field surveys in Croatia and North Macedonia reveal two novel phleboviruses circulating in sandflies.

Sandfly-borne phleboviruses are distributed widely throughout the Mediterranean Basin, presenting a threat to public health in areas where they circulate. However, the true diversity and distribution of pathogenic and apathogenic sandfly-borne phleboviruses remains a key issue to be studied. In the Balkans, most published data rely on serology-based studies although virus isolation has occasionally been reported. Here, we report the discovery of two novel sandfly-borne phleboviruses, provisionally named Zaba virus (ZABAV) and Bregalaka virus (BREV), which were isolated in Croatia and North Macedonia, respectively. This constitutes the first isolation of phleboviruses in both countries. Genetic analysis based on complete coding sequences indicated that ZABAV and BREV are distinct from each other and belong to the genus Phlebovirus, family Phenuiviridae. Phylogenetic and amino acid modelling of viral polymerase shows that ZABAV and BREV are new members of the Salehabad phlebovirus species and the Adana phlebovirus species, respectively. Moreover, sequence-based vector identification suggests that ZABAV is mainly transmitted by Phlebotomus neglectus and BREV is mainly transmitted by Phlebotomus perfiliewi. BREV neutralizing antibodies were detected in 3.3% of human sera with rates up to 16.7% in certain districts, demonstrating that BREV frequently infects humans in North Macedonia. In vitro viral growth kinetics experiments demonstrated viral replication of both viruses in mammalian and mosquito cells. In vivo experimental studies in mice suggest that ZABAV and BREV exhibit characteristics making them possible human pathogens.

Further Characterization of Rio Grande Virus and Potential for Cross Reactivity with Rift Valley Fever Virus Assays.

Phleboviruses (genus Phlebovirus, family Phenuiviridae) are emerging pathogens of humans and animals. Sand-fly-transmitted phleboviruses are found in Europe, Africa, the Middle East, and the Americas, and are responsible for febrile illness and nervous system infections in humans. Rio Grande virus (RGV) is the only reported phlebovirus in the United States. Isolated in Texas from southern plains woodrats, RGV is not known to be pathogenic to humans or domestic animals, but serologic evidence suggests that sheep (Ovis aries) and horses (Equus caballus) in this region have been infected. Rift Valley fever virus (RVFV), a phlebovirus of Africa, is an important pathogen of wild and domestic ruminants, and can also infect humans with the potential to cause severe disease. The introduction of RVFV into North America could greatly impact U.S. livestock and human health, and the development of vaccines and countermeasures is a focus of both the CDC and USDA. We investigated the potential for serologic reagents used in RVFV diagnostic assays to also detect cells infected with RGV. Western blots and immunocytochemistry assays were used to compare the antibody detection of RGV, RVFV, and two other New World phlebovirus, Punta Toro virus (South and Central America) and Anhanga virus (Brazil). Antigenic cross-reactions were found using published RVFV diagnostic reagents. These findings will help to inform test interpretation to avoid false positive RVFV diagnoses that could lead to public health concerns and economically costly agriculture regulatory responses, including quarantine and trade restrictions.

Phylogenetic Analysis of Massilia phlebovirus in Portugal.

In the last two decades, molecular surveys of arboviruses have enabled the identification of several new viruses, contributing to the knowledge of viral diversity and providing important epidemiological data regarding possible new emerging viruses. A combination of diagnostic assays, Illumina sequencing and phylogenetic inference are here used to characterize two new Massilia phlebovirus strains isolated from sandflies collected in the Arrábida region, Portugal. Whole genome sequence analysis enabled their identification as reassortants and the recognition of genomic variants co-circulating in Portugal. Much is still unknown about the life cycle, geographic range, evolutionary forces and public health importance of these viruses in Portugal and elsewhere, and more studies are needed.

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

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

Clinically Important Phleboviruses and Their Detection in Human Samples.

The detection of phleboviruses (family: Phenuiviridae) in human samples is challenged by the overall diversity and genetic complexity of clinically relevant strains, their predominantly nondescript clinical associations, and a related lack of awareness among some clinicians and laboratorians. Here, we seek to inform the detection of human phlebovirus infections by providing a brief introduction to clinically relevant phleboviruses, as well as key targets and approaches for their detection. Given the diversity of pathogens within the genus, this report focuses on diagnostic attributes that are generally shared among these agents and should be used as a complement to, rather than a replacement of, more detailed discussions on the detection of phleboviruses at the individual virus level.

Serological Evidence of Phleboviruses in Domestic Animals on the Pre-Apennine Hills (Northern Italy).

Phleboviruses are arboviruses transmitted by sand flies, mosquitoes and ticks. Some sand fly-borne phleboviruses cause illnesses in humans, such as the summer fevers caused by the Sicilian and Naples viruses or meningitis caused by the Toscana virus. Indeed, traces of several phleboviral infections have been serologically detected in domestic animals, but their potential pathogenic role in vertebrates other than humans is still unclear, as is the role of vertebrates as potential reservoirs of these viruses. In this study, we report the results of a serological survey performed on domestic animals sampled in Northern Italy, against four phleboviruses isolated from sand flies in the same area. The sera of 23 dogs, 165 sheep and 23 goats were tested with a virus neutralization assay for Toscana virus, Fermo virus, Ponticelli I virus and Ponticelli III virus. Neutralizing antibodies against one or more phleboviruses were detected in four out of 23 dogs, 31 out of 165 sheep and 12 out of 23 goats. This study shows preliminary evidence for the distribution pattern of phleboviral infections in different animal species, highlighting the potential infection of the Toscana virus in dogs and the Fermo virus in goats.

Severe Fever with Thrombocytopenia Syndrome in Cats and Its Prevalence among Veterinarian Staff Members in Nagasaki, Japan.

In this study, we investigated severe fever with thrombocytopenia syndrome (SFTS) virus (SFTSV) infection in cats in Nagasaki, Japan. In total, 44 of 133 (33.1%) cats with suspected SFTS were confirmed to be infected with SFTSV. Phylogenetic analyses of SFTSV isolates from cats indicated that the main genotype in Nagasaki was J1 and that unique reassortant strains with J2 (S segment) and unclassified genotypes (M and L segments) were also present. There were no significant differences in virus growth in cell cultures or fatality in SFTSV-infected mice between the SFTSV strains that were isolated from recovered and fatal cat cases. Remarkably, SFTSV RNAs were detected in the swabs from cats, indicating that the body fluids contain SFTSV. To evaluate the risk of SFTSV infection when providing animal care, we further examined the seroprevalence of SFTSV infection in veterinarian staff members; 3 of 71 (4.2%) were seropositive for SFTSV-specific antibodies. Our results provide useful information on the possibility of using cats as sentinel animals and raised concerns of the zoonotic risk of catching SFTSV from animals.

Unraveling the Underlying Interaction Mechanism Between Dabie bandavirus and Innate Immune Response.

The genus Bandavirus consists of seven tick-borne bunyaviruses, among which four are known to infect humans. Dabie bandavirus, severe fever with thrombocytopenia syndrome virus (SFTSV), poses serious threats to public health worldwide. SFTSV is a tick-borne virus mainly reported in China, South Korea, and Japan with a mortality rate of up to 30%. To date, most immunology-related studies focused on the antagonistic role of SFTSV non-structural protein (NSs) in sequestering RIG-I-like-receptors (RLRs)-mediated type I interferon (IFN) induction and type I IFN mediated signaling pathway. It is still elusive whether the interaction of SFTSV and other conserved innate immune responses exists. As of now, no specific vaccines or therapeutics are approved for SFTSV prevention or treatments respectively, in part due to a lack of comprehensive understanding of the molecular interactions occurring between SFTSV and hosts. Hence, it is necessary to fully understand the host-virus interactions including antiviral responses and viral evasion mechanisms. In this review, we highlight the recent progress in understanding the pathogenesis of SFTS and speculate underlying novel mechanisms in response to SFTSV infection.

Taxonomy of Phleboviruses, Emphasizing Those That Are Sandfly-Borne.

Sandfly-borne phleboviruses (phylum Negarnavaricota, realm Riboviria, kingdom Orthornavirae, genus Phlebovirus) comprise three genome segments of ribonucleic acid (RNA) and which encode an RNA-dependent RNA polymerase, which they use to transcribe the viral RNA genome into messenger RNA and to replicate the genome. At least some of these viruses cause mild 3-day fevers in humans but some also have been associated with more severe illnesses in humans. The 67 recognized phleboviruses are listed here in a table composed by the authors from International Committee on Taxonomy of Viruses reports as well as the scientific literature.

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.

Isolation and Identification of a Novel Phlebovirus, Hedi Virus, from Sandflies Collected in China.

We report the isolation of a newly recognized phlebovirus, Hedi virus (HEDV), from Phlebotomus chinensis sandflies collected in Shanxi Province, China. The virus' RNA is comprised of three segments. The greatest amino acid sequence similarity of the three gene segments between this virus and previously recognized phleboviruses is 40.85-63.52%, and the RNA-dependent RNA polymerase (RdRp) amino acid sequence has the greatest similarity (63.52%) to the Rift Valley fever virus (RVFV) ZH-548 strain. Phylogenetic analysis of the amino acid sequence of the virus RdRp indicated that HEDV is close to RVFV and distinct from other phleboviruses, forming its own evolutionary branch. We conclude that it is necessary to increase the monitoring of phleboviruses carried by sandflies in China.

Thirteen Years of Phleboviruses Circulation in Lombardy, a Northern Italy Region.

Phleboviruses transmitted by phlebotomine sandflies are endemic in the Mediterranean basin. Toscana phlebovirus (TOSV), Sicilian phlebovirus (SFSV), and Naples phlebovirus (SFNV) are responsible of summer fever, with well-known pathogenic potential for humans ranging from asymptomatic to mild fever, in addition to neuro-invasive infections during summer. Although TOSV, in particular, is a significant and well-known human pathogen, SFVs remain neglected, with many gaps in the relevant knowledge. Sero-epidemiological studies and case reports recently showed a geographical wider distribution than previously considered, although the real incidence of phleboviruses infections in the Mediterranean area is still unknown. Here we retrospectively evaluated the circulation of phleboviruses during summer seasons between 2007 and 2019 in 649 patients showing neurological symptoms using both molecular and serological approaches. We found that 42/649 (6.5%) subjects experienced phlebovirus infection and only 10/42 cases were detected by molecular assays, whereas the other 32/42 were identified using serological approaches, including neutralization assays. During the 2013 summer, an outbreak in the Lombardy region is described because the prevalence of phlebovirus infection reached 37.2% (19/51 subjects). Interestingly, only 5/19 (26.5%) reported traveling in endemic areas. Of note, no cross-neutralization was observed between different strains tested, showing the possibility to be reinfected by newly discovered phlebovirus strains. In conclusion, phlebovirus infections are still inadequately considered by physicians and are generally underestimated. However, based on our results, sandfly fever viruses should be routinely included in diagnostic panels during summer period, including in Northern Italy.

Changes in peripheral blood cytokines in patients with severe fever with thrombocytopenia syndrome.

Severe fever with thrombocytopenia syndrome (SFTS) is recognized as an emerging infectious disease. This study aimed to investigate the pathogenic mechanism of SFTS. A total of 100 subjects were randomly included in the study. Cytokine levels were detected by enzyme-linked immunosorbent assay and the viral load was detected by micro drop digital PCR. The results showed that levels of interleukin-6 (IL-6), IL-8, IL-10, IFN-inducible protein-10 (IP-10), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α), transforming growth factor-ß1 (TGF-ß1), and regulated upon activation normal T cell expressed and secreted factor (RANTES) differed significantly among the SFTS patient group, healthy people group, and asymptomatic infection group (p < .05). Compared to the healthy people group, the patient group had increased cytokine levels (IL-6, IL-10, IP-10, MCP-1, and IFN-γ) but reduced levels of IL-8, TGF-ß1, and RANTES (p < .0167). IL-6, IL-8, IL-10, IP-10, MCP-1, MIP-1α, TGF-ß1, and the RANTES levels had different trends after the onset of the disease. IL-6, IL-10, IP-10, and MCP-1 levels in severe patients were higher than those in mild patients (p < .05). There was a positive correlation between viral load and IL-6 and IP-10 but a negative correlation between viral load and RANTES. SFTSV could cause a cytokine change: the cytokine levels of patients had different degrees of fluctuation after the onset of the disease. The levels of IL-6 and IL-8 in the asymptomatic infection group were found between the SFTS patients group and the healthy people group. The levels of IL-6, IL-10, IP-10, and MCP-1 in the serum could reflect the severity of the disease, and the levels of IL-6, IP-10, and RANTES were correlated with the viral load.

Two Different Strains of Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) in North and South Osaka by Phylogenetic Analysis of Evolutionary Lineage: Evidence for Independent SFTSV Transmission.

Severe fever with thrombocytopenia syndrome (SFTS) is a novel tick-borne infectious disease, therefore, the information on the whole genome of the SFTS virus (SFTSV) is still limited. This study demonstrates a nearly whole genome of the SFTSV identified in Osaka in 2017 and 2018 by next-generation sequencing (NGS). The evolutionary lineage of two genotypes, C5 and J1, was identified in Osaka. The first case in Osaka belongs to suspect reassortment (L:C5, M:C5, S:C4), the other is genotype J1 (L: J1, M: J1, S: J1) according to the classification by a Japanese group. C5 was identified in China, indicating that C5 identified in this study may be transmitted by birds between China and Japan. This study revealed that different SFTSV genotypes were distributed in two local areas, suggesting the separate or focal transmission patterns in Osaka.

The NF-κB inhibitor, SC75741, is a novel antiviral against emerging tick-borne bandaviruses.

Severe fever with thrombocytopenia syndrome virus (SFTSV) and Heartland virus (HRTV) cause viral hemorrhagic fever-like illnesses in humans due to an aberrant host inflammatory response, which contributes to pathogenesis. Here, we established two separate minigenome (MG) systems based on the M-segment of SFTSV and HRTV. Following characterization of both systems for SFTSV and HRTV, we used them as a platform to screen potential compounds that inhibit viral RNA synthesis. We demonstrated that the NF-κB inhibitor, SC75741, reduces viral RNA synthesis of SFTSV and HRTV using our MG platform and validated these results using infectious SFTSV and HRTV. These results may lead to the use of MG systems as potential screening systems for the identification of antiviral compounds and yield novel insights into host-factors that could play role in bandavirus transcription and replication.

Phlebovirus sequences detected in ticks collected in Russia: Novel phleboviruses, distinguishing criteria and high tick specificity.

Phlebovirus is an abundant and rather heterogeneous genus within the Phenuiviridae family (order Bunyavirales). The genus Phlebovirus is divided into two antigenic complexes, which also correspond to the main vector: sandflies/mosquitoes and ticks. Previously, only sandfly/mosquito-borne phleboviruses were associated with human disease, such as Rift Valley fever virus, Toscana virus, Sicilian and Naples Sandfly fever viruses and others. Until recently, tick-borne phleboviruses were not considered as human pathogens. After the discovery of severe fever with thrombocytopenia syndrome, interest to tick-borne phleboviruses has increased dramatically. In the last decade, many novel phleboviruses have been reported in different regions. Despite this, the diversity, ecology and pathogenicity of these viruses still remain obscure. The aim of this work was to study the diversity of phleboviruses in ticks collected in several regions of Russia. We used pan-phlebovirus RT-PCR assays based on multiple degenerate primers targeting the polymerase gene fragment. Arthropod specimens were collected from 2005 to 2018. A total of 5901 Ixodidae ticks combined into 1116 pools were screened. A total of 160 specific amplicons were produced. In three cases RT-PCR assays amplified two distinct viruses from same tick pools. Direct sequencing of amplicons and subsequent phylogenetic analysis revealed twelve representatives of divergent phlebovirus groups. Based on the distribution of pairwise nucleotide sequence identity values, a cut-off (88%) was suggested to distinguish tick-borne phleboviruses. According to this provisional criterion, two viruses found here could be termed novel, while ten viruses have been described in previous studies. Detected phleboviruses demonstrated almost perfect specificity to a tick species or, at least, a genus. The same pattern was observed for tick-borne phleboviruses found in different studies around the world. Viruses that grouped together on a phylogenetic tree and differed less than this sequence identity threshold suggested above were hosted by ticks from the same genus.