Isolation of Japanese encephalitis virus and a novel insect-specific flavivirus from mosquitoes collected in a cowshed in Japan

Abstract

Cattle do not generally appear to develop severe viremia when infected with Japanese encephalitis virus (JEV), and they can be infected without showing clinical signs. However, two cattle in Japan recently died from JEV infection. In this study, we investigated the presence of different species of mosquitoes and flavivirus in a cowshed in the southwest region of Japan. In this cowshed, the two most common species of mosquitoes collected were Culex tritaeniorhynchus (including Culex pseudovishnui) and Anopheles sinensis. We performed virus isolation from the collected mosquitoes and obtained two flaviviruses: JEV and a novel insect-specific flavivirus, tentatively designated Yamadai flavivirus (YDFV). Phylogenetic analysis revealed that all three JEV isolates belonged to JEV genotype I and were closely related to a JEV strain that was isolated from the brains of cattle exhibiting neurological symptoms in Japan. Genetic characterization of YDFV revealed that the full genome RNA (10,863 nucleotides) showed homology with the Culex-associated insect-specific flaviviruses Quang Binh virus (79% identity) and Yunnan Culex flavivirus (78% identity), indicating that YDFV is a novel insect-specific flavivirus.

Distribution of Japanese Encephalitis Virus, Japan and Southeast Asia, 2016–2018

“…In a phylogenetic analysis, these viruses clustered with JEV isolates recovered from Japan (in 2013 and 2009), China (in 2007), and South Korea (in 2010) (Figure, panel A). The 2 viruses collected in Japan in 2016 were most closely related to viruses recovered in 2013 from the same site that had been sampled in our previous study ( 10 ), suggesting that this strain has been maintained in the Yamaguchi area of Japan since at least 2013.…”

A Systematic Review of the Natural Virome of Anopheles Mosquitoes

“…JEV genotype I was isolated from host-seeking An. sinensis collected by aspirator in Japan [ 46 ]. An.…”

Mosquito-borne viruses, insect-specific flaviviruses (family <i>Flaviviridae</i>, genus <i>Flavivirus</i>), Banna virus (family <i>Reoviridae</i>, genus <i>Seadornavirus</i>), Bogor virus (unassigned member of family <i>Permutotetraviridae</i>), and alphamesoniviruses 2 and 3 (family <i>Mesoniviridae</i>, genus <i>Alphamesonivirus</i>) isolated from Indonesian mosquitoes

“…Virus isolation was performed as previously described [ 28 , 29 ]. Each pool of mosquitoes was homogenized in 500 µl of ice-cold DMEM containing 2% heat-inactivated FBS and 1% Pen-Strep using the Multi-beads shocker (Yasui Kikai Inc., Osaka, Japan).…”