Omono River virus (OmRV) is a double-stranded RNA virus isolated from Culex mosquitos, and it belongs to a group of unassigned insect viruses that appear to be related to Totiviridae. This paper describes electron cryo-microscopy (cryoEM) structures for the intact OmRV virion to 8.9 Å resolution and the structure of the empty virus-like-particle, that lacks RNA, to 8.3 Å resolution. The icosahedral capsid contains 120-subunits and resembles another closely related arthropod-borne totivirus-like virus, the infectious myonecrosis virus (IMNV) from shrimps. Both viruses have an elevated plateau around their icosahedral 5-fold axes, surrounded by a deep canyon. Sequence and structural analysis suggests that this plateau region is mainly composed of the extended C-terminal region of the capsid proteins. In contrast to IMNV, the infectious form of OmRV lacks extensive fibre complexes at its 5-fold axes as directly confirmed by a contrast-enhancement technique, using Zernike phase-contrast cryo-EM. Instead, these fibre complexes are replaced by a short “plug” structure at the five-fold axes of OmRV. OmRV and IMNV have acquired an extracellular phase, and the structures at the five-fold axes may be significant in adaptation to cell-to-cell transmission in metazoan hosts.

Aedes aegypti (Linnaeus, 1762) is the main mosquito vector for dengue and other arboviral infectious diseases. Control of this important vector highly relies on the use of insecticides, especially pyrethroids. The high frequency (>78%) of the L982W substitution was detected at the target site of the pyrethroid insecticide, the voltage-gated sodium channel (Vgsc) of A. aegypti collected from Vietnam and Cambodia. Alleles having concomitant mutations L982W + F1534C and V1016G + F1534C were also confirmed in both countries, and their frequency was high (>90%) in Phnom Penh, Cambodia. Strains having these alleles exhibited substantially higher levels of pyrethroid resistance than any other field population ever reported. The L982W substitution has never been detected in any country of the Indochina Peninsula except Vietnam and Cambodia, but it may be spreading to other areas of Asia, which can cause an unprecedentedly serious threat to the control of dengue fever as well as other Aedes -borne infectious diseases.

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Aedes aegypti (Linnaeus, 1762) is the main mosquito vector for dengue and other arboviral infectious diseases. Control of this important vector highly relies on the use of insecticides, especially pyrethroids. Nevertheless, the development of pyrethroid resistance is a major obstacle to mosquito/disease control worldwide. Here, we focused on the mutations in the target site of pyrethroid insecticides, voltage-sensitive sodium channel (Vssc), and found that Ae. aegypti collected from Vietnam has the L982W allele in the Vssc at a high frequency (>79%). L982W mutation is located in the highly conserved region of Vssc that is associated with sodium-ion selectivity and permeation rate. Strains having the L982W allele showed similar or even higher levels of resistance to pyrethroids than those having V1016G, a typical knockdown resistance allele in Asia. Furthermore, concomitant mutations L982W+F1534C and V1016G+F1534C were confirmed, and strains having these multiple Vssc mutations exhibited incomparably higher levels of pyrethroid resistance than any other field population ever reported. Molecular modeling analysis confirmed that these concomitant mutant alleles could interfere with approaching pyrethroid to Vssc. Remarkably, >90% of Vssc of Ae. aegypti were occupied by these hyper insecticide-resistant haplotypes in Phnom Penh city, Cambodia. Analysis of whole Vssc coding genes suggested that Vsscs have evolved into stronger resistant forms efficiently through gene recombination events. At this point, L982W has never been detected in Vssc of Ae. aegypti from any other neighboring countries. We strongly emphasize the need to be vigilant about these strong resistance genes spreading to the world through Indochina Peninsula.