Publications by authors named "Ryusei Kuwata"

Article Synopsis
  • Getah virus (GETV) is a mosquito-borne virus that affects horses and pigs, causing symptoms like fever and rash, and has been reported in outbreaks primarily in Asia and Oceania.
  • A new strain of GETV (22IH8) was isolated from mosquitoes in Nagasaki, Japan in 2022, and genetic analysis shows it is more closely related to strains from China than those found in Japan in the past.
  • The current vaccine for horses in Japan (MI-110) is effective against the new strain, suggesting that existing vaccination efforts can still combat this emerging threat.
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Orientia tsutsugamushi (OT) is an obligate intracellular bacterium transmitted by larval trombiculid mites, responsible for scrub typhus in humans. In Japan, approximately 500 human cases are reported annually, with six major serotypes identified as Kato, Karp, Gilliam, Irie/Kawasaki, Shimokoshi, and Hirano/Kuroki. However, the prevalence of OT in Yamaguchi prefecture remains largely unknown.

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  • Cervus nippon (sika deer) are common in eastern Asia and have antibodies against zoonotic pathogens, serving as potential reservoirs for diseases.
  • This study focused on developing and analyzing cultured cells from sika deer testicular tissue, confirming their origin from Japanese sika deer and their characteristics as a mixed cell population.
  • The cultured cells showed susceptibility to various arthropod-borne viruses in Japan, supporting their utility in understanding sika deer as a source of zoonoses and aiding research at the cellular and molecular levels.
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It is extremely rare that a single virus crosses host barriers across multiple kingdoms. Based on phylogenetic and paleovirological analyses, it has previously been hypothesized that single members of the family could cross multiple kingdoms. accommodates members characterized by their simple bisegmented double-stranded RNA genome; asymptomatic infections of host organisms; the absence of an extracellular route for entry in nature; and collectively broad host range.

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  • * SAYAV was not able to be cultured in lab settings but was studied by creating single-round infectious virus particles (SRIP) using its gene sequence, which helped in examining its endemic status.
  • * The presence of neutralizing antibodies against SAYAV in sika deer and wild boars indicates it is widespread in Japan, and phylogenetic analysis shows it evolved separately from other known flaviviruses, highlighting an innovative approach to studying uncultured viruses.
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  • Getah virus (GETV), which is spread by mosquitoes and affects various animals, causes fever, rash, and leg edema in infected horses.
  • The study focused on Noma horses, a native breed in Japan, to investigate the occurrence of GETV infections among them.
  • Serum tests revealed that anti-GETV antibody levels in Noma horses were significantly higher in samples from 2017 compared to those from 2012, indicating an epidemic of GETV in Japan around 2012.
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Severe fever with the thrombocytopenia syndrome virus (SFTSV) causes fatal disease in humans, cats, and cheetahs. In this study, the information on seven dogs with SFTS was summarized. All dogs showed anorexia, high fever, leukopenia, and thrombocytopenia, two dogs showed vomiting and loose stool, and five dogs had tick parasites.

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Article Synopsis
  • * A retrospective surveillance revealed that a significant percentage of the tested animals had antibodies against SFTSV: 510 out of 789 sika deer and 199 out of 517 wild boars.
  • * The findings suggest that SFTSV had been present in wild animals prior to 2012, with a noticeable increase in infection rates in sika deer from 2010-2013 to 2015-2020, indicating a gradual spread of the virus in the area
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The Culex vishnui subgroups, particularly Culex tritaeniorhynchus, are considered the primary vectors of the Japanese encephalitis virus (JEV) in Asia. Recent molecular phylogenetic analyses of JEV isolates from Asian countries have shown that JEVs with diverse genetic variants are present in Asia. Furthermore, some JEV strains have been found to have crossed the East China Sea and been introduced into Japan.

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In Japan, hepatitis E virus (HEV) causes hepatitis in humans through the consumption of raw or undercooked meat, including game meat. In the present study, nationwide surveillance of HEV infection among a total of 5,557 wild animals, including 15 species, was conducted in Japan. The prevalence of anti-HEV antibodies in wild boar was 12.

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Article Synopsis
  • Japanese encephalitis virus (JEV) is primarily transmitted in the Asian-Pacific region through Culex tritaeniorhynchus mosquitoes and affects humans severely.
  • Researchers discovered JEV in unfed Haemaphysalis flava ticks collected in Japan, even during months when the main mosquito vector was not active.
  • The findings include detection of JEV RNA in ticks and some evidence of viral replication, but there’s still uncertainty whether ticks serve as a reservoir for the virus since no infectious JEV was isolated.
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Oz virus is a novel thogotovirus isolated from ticks that causes lethal infection in mice. We conducted serosurveillance of Oz virus infection among humans and wild mammals in Japan using virus-neutralization tests and ELISAs. Results showed that Oz virus may be naturally infecting humans and other mammalian hosts.

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  • Jingmen tick virus (JMTV) and Alongshan virus are emerging tick-borne viruses linked to human infections, found in various mammals and invertebrates, but their transmission cycles are not fully understood.
  • Recent surveillance in Japan identified JMTV and a new related virus, Takachi virus (TAKV), showing JMTV's widespread presence and persistence in certain regions over multiple years.
  • Evidence suggests that JMTV may be transmitted vertically in ticks, highlighting the need for further research to understand the infection risks associated with jingmenviruses in Japan.
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Rabbit hepatitis E virus (HEV) has been detected among rabbits and recently isolated from immunocompromised patients, suggesting zoonotic transmission. In this study, HEV infection among feral rabbits (Oryctolagus cuniculus) was assessed by detection of anti-HEV antibodies and HEV RNA. The prevalence of anti-HEV antibodies in sera was of 33 % (20/60) and HEV RNA was detected from only one of fecal swabs (1.

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The family is a nonenveloped virus group with a double-stranded (ds) RNA genome comprising 9 to 12 segments. In the family , the genera , , , , and contain virus species having 12-segmented dsRNA genomes. Reverse genetics systems used to generate recombinant infectious viruses are powerful tools for investigating viral gene function and for developing vaccines and therapeutic interventions.

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  • Researchers have identified novel quaranjavirus-like sequences in ticks from Ehime Prefecture, Japan, hinting at new viruses that could infect humans.
  • The viruses were related to previously detected viruses such as Zambezi tick virus 1 from Africa and Uumaja virus from Europe, suggesting a potential new group within the Quaranjavirus genus.
  • This discovery marks the first detection of a quaranjavirus-like virus in East Asia and highlights the need for further studies to understand their risks and effects on human and animal health.
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Ticks are important vector arthropods that transmit various pathogens to humans and other animals. Tick-borne viruses are of particular concern to public health as these are major agents of emerging and re-emerging infectious diseases. The Phenuiviridae family of tick-borne viruses is one of the most diverse groups and includes important human pathogenic viruses such as severe fever with thrombocytopenia syndrome virus.

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Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tickborne infectious disease caused by SFTS virus (SFTSV). We report 7 cases of spontaneous fatal SFTS in felines. Necropsies revealed characteristic lesions, including necrotizing lymphadenitis in 5 cases and necrotizing splenitis and SFTSV-positive blastic lymphocytes in all cases.

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Getah virus (GETV) is a mosquito-borne RNA virus belonging to the family Togaviridae, genus Alphavirus. GETV infection causes diarrhoea and death in piglets, and reproductive failure and abortion in sows. This study conducted a serological survey of GETV infection among domestic pig populations in Thailand.

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In this study, we examined the role of the eastern bent-winged bat (Miniopterus fuliginosus) in the dispersion of bat adenovirus and bat alphacoronavirus in east Asia, considering their gene flows and divergence times (based on deep-sequencing data), using bat fecal guano samples. Bats in China moved to Jeju Island and/or Taiwan in the last 20,000 years via the Korean Peninsula and/or Japan. The phylogenies of host mitochondrial D-loop DNA was not significantly congruent with those of bat adenovirus (m2XY = 0.

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Mosquitoes are generally considered one of the most important vectors of arboviruses, with Aedes aegypti regarded as the most important in transmission of yellow fever and dengue viruses. To investigate why there are differences in the incidence of dengue fever and Zika in different geographical areas and an absence of outbreaks in Ghana in spite of an abundance of A. aegypti mosquitoes, we established a continuous cell line from embryonic cells of A.

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Mosquitoes transmit many kinds of arboviruses (arthropod-borne viruses), and numerous arboviral diseases have become serious problems in Indonesia. In this study, we conducted surveillance of mosquito-borne viruses at several sites in Indonesia during 2016-2018 for risk assessment of arbovirus infection and analysis of virus biodiversity in mosquito populations. We collected 10,015 mosquitoes comprising at least 11 species from 4 genera.

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During 2016-2018, we conducted surveillance for Japanese encephalitis virus (JEV) in mosquitoes and pigs in Japan, Thailand, the Philippines, and Indonesia. Phylogenetic analyses demonstrated that our isolates (genotypes Ia, Ib, III, IV) were related to JEV isolates obtained from the same regions many years ago. Indigenous JEV strains persist in Asia.

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Ticks are one of the arthropods that play an important role in the transmission of numerous pathogens to livestock and humans. We investigated the presence of tick-borne bacteria in 23 Amblyomma varanense that fed on a water monitor (Varanus salvator) in Indonesia. Anaplasmataceae and borreliae were detected by PCR in 17.

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Tick-borne encephalitis virus (TBEV), a flavivirus that causes severe neurological symptoms in humans, has been found in Hokkaido, Japan. In the present study, we detected sequences from a novel tick-borne flavivirus, designated Yamaguchi virus (YGV), in liver and serum samples obtained from a wild boar in the Yamaguchi prefecture, Japan. Phylogenetic analysis revealed that YGV belongs to the TBEV complex and is closely related to Langat virus (LGTV).

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