Publications by authors named "Hiroko Ejiri"

Ticks are blood-sucking arthropods that transmit many pathogens, including arboviruses. Arboviruses transmitted by ticks are generally referred to as tick-borne viruses (TBVs). TBVs are known to cause diseases in humans, pets, and livestock.

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  • Tick-borne viruses are increasingly being identified globally, with advancements in high-throughput sequencing technology aiding their discovery.
  • This study utilized the Illumina MiniSeq to analyze the RNA virome of questing ticks from Japan, resulting in the isolation of several novel viruses, including two phleboviruses, one coltivirus, and one iflavirus.
  • Phylogenetic analysis indicated that certain recently discovered phleboviruses may be deficient in a specific genome segment, offering new insights into their evolution and potential as emerging pathogens.
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In 2014 in Japan, 162 autochthonous dengue cases were reported for the first time in nearly 70 years. Here, we report the results of the detection and isolation of dengue virus (DENV) from mosquitoes collected in Tokyo Metropolis in 2014 and 2015. The phylogenetic relationship among DENV isolates from mosquitoes and from patients based on both the entire envelope gene and whole coding sequences was evaluated.

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  • The Thogotovirus genus includes tick-borne viruses like Thogoto and Dhori viruses, and a new virus called Oz virus (OZV) has been isolated from ticks in Japan.
  • OZV has shown efficient replication in various cell types and can cause high mortality in young mice when introduced to the brain.
  • Genetic analysis reveals that OZV is closely related to the Bourbon virus, highlighting the importance of studying its ecology and potential health risks.
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In Japan, indigenous tick-borne phleboviruses (TBPVs) and their associated diseases first became evident in 2013 by reported human cases of severe fever with thrombocytopenia syndrome (SFTS). In this study, we report a novel member of the genus Phlebovirus designated as Kabuto Mountain virus (KAMV), which was isolated from the ixodid tick Haemaphysalis flava in Hyogo, Japan. A complete viral genome sequencing and phylogenetic analyses showed that KAMV is a novel member of TBPVs, which is closely related to the Uukuniemi and Kaisodi group viruses.

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  • - Three similar isolates of a novel virus, named Tarumizu tick virus (TarTV), were discovered from hard ticks in Japan, showing they are closely related yet distinct strains.
  • - TarTV has a genome consisting of 12 double-stranded RNA segments, with 10 segments exhibiting similarities to proteins of other known tick-borne viruses, indicating it may belong to the Coltivirus genus.
  • - Electron microscopy revealed TarTV has a non-enveloped icosahedral structure, and while it can replicate in mammalian cells, it does not cause symptoms in infected mice, highlighting its potential for further study on genetic diversity within the Coltivirus family.
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  • Getah virus (GETV) is a mosquito-borne virus affecting horses and pigs, with a notable outbreak in racehorses in Japan in 2014, the first in about 30 years.
  • Researchers had previously collected mosquito samples in Nagasaki and sequenced a GETV strain (12IH26), which turned out to be nearly identical (99.9%) to the strains from the 2014 outbreak.
  • Phylogenetic analysis indicated that recent GETV strains in Japan are more similar to those from China and South Korea, implying that the virus might have been introduced to Japan via infected mosquitoes or migratory birds.
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  • Researchers have identified a new tick-borne orbivirus from Ixodes turdus ticks in Japan, naming it Muko virus (MUV), which is part of the Great Island virus species.
  • MUV was found to replicate in various cell lines and caused high mortality in suckling mice when injected.
  • The full genome analysis reveals that MUV shares significant similarities with Tribeč virus, contributing to the understanding of genetic diversity and evolution within the Great Island virus species.
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An orbivirus was isolated from a sample from the ornithophilic mosquito Culex sasai in Japan. The virus, designated Koyama Hill virus (KHV), replicated to high titer in a mosquito cell line and to a low titer in an avian cell line, but the release of progeny viruses was not observed in mammalian cell lines inoculated with KHV. Electron microscopic examination of KHV-infected mosquito cells showed approximately 70-nm virus particles and viral tubules typical of members of the genus Orbivirus, family Reoviridae.

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We investigated for the first time the prevalence of avian haemosporidia of genera Plasmodium, Haemoproteus and Leucocytozoon among birds and mosquitoes on Tsushima Island of Japan, which is located between Japan and the Korean Peninsula. Of 55 wild birds belonging to 33 species, 16 (29.1%) tested positive for haemosporidia as follows: Plasmodium spp.

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In Japan, the prevalence of avian Plasmodium in birds and mosquitoes has been partially examined in the temperate and subtropical zones; however, mosquitoes in the Japanese subarctic zone have not been adequately investigated. In this study, mosquito collections and avian Plasmodium detections from the mosquito samples were carried out to demonstrate the avian Plasmodium transmission between vector mosquitoes and birds inhabiting in Kushiro Wetland, subarctic zone of Japan. A total of 5657 unfed mosquitoes from 18 species and 320 blood-fed mosquitoes from eight species was collected in summer 2008, 2009, and 2010.

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The infection dynamics of avian haematozoa, which includes the genera Plasmodium, Haemoproteus, and Leucocytozoon, are complicated by a variety of environmental factors and host-parasite interactions. In Japan, the prevalence of haematozoa in wild birds has recently been determined in several local areas. However, no information on the annual prevalence of avian haematozoa in a single study site has been reported.

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  • Researchers analyzed 509 mosquitoes from 9 species on Ishigaki and Iriomote islands in Japan's Yaeyama Archipelago for avian Plasmodium prevalence.
  • They found two identical avian Plasmodium lineages in Culex (Culiciomyia) nigropunctatus, which were distinct from those in mainland Japan.
  • This marks the first detection of avian Plasmodium DNA in mosquitoes in this region, suggesting that local resident birds may be infected and that C. nigropunctatus could serve as the primary mosquito vector.
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Several species of captive and wild birds have been found to be infected with various avian blood protozoa in Japan. We investigated the prevalence and transmission of avian malaria parasite and determined the bloodmeal hosts of mosquitoes collected in a zoological garden in Tokyo, Japan, by using the polymerase chain reaction. In total, 310 unfed and 140 blood-fed mosquitoes of seven species were collected by using sweep nets and CDC traps.

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One of vector-borne avian protozoa, Leucocytozoon lovati, has been found in the Japanese rock ptarmigans (Lagopus mutus japonicus), the endangered bird species distributed in the alpine regions in Japan. Vector arthropod species of L. lovati has also been estimated as Simuliidae black flies distributed in the same habitat of the host bird, however, possible blood meals of the black flies were not identified yet.

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Several species of captive birds at zoological gardens of Japan were found to be infected with avian Plasmodium. However, incriminated vector mosquito species have not been identified yet. To indicate the competent vectors of avian malaria parasite, we collected mosquitoes at a zoological garden in Japan and examined for the avian malaria parasite DNA.

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  • Researchers found that several bird species on Minami Daito Island in Japan are infected with avian Plasmodium, but the specific mosquito vectors responsible remain unclear.
  • They collected 1,264 mosquitoes over a year and tested 399 DNA samples, finding a 1.2% infection rate for avian Plasmodium among them.
  • Four mosquito species were identified as potential vectors: Aedes albopictus, Culex quinquefasciatus, Lutzia fuscanus, and Mansonia sp., with some DNA sequences matching known avian Plasmodium lineages from local birds.
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Probable arthropod vectors of avian blood protozoa, Leucocytozoon lovati, were collected in the alpine regions of Japan, the habitats of the host birds of Japanese rock ptarmigan (Lagopus mutus japonicus). Seven alpine regions of Japan, Asahidake, Chogatake, Tateyama, Jiigatake, Norikura, Kitadake, and Senjyogatake were investigated for black fly collection during 2004 to 2007. The collected 490 insects were morphologically identified as six species of female black flies, including Prosimulium hirtipes group (n = 59), Prosimulium mutata (n = 13), Prosimulium yezoense (n = 10), Similium japonicum (n = 359), Similium uchidai (n = 39), and Twinnia japonensis (n = 10).

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