Identification, surveillance and management of Aedes vexans in a flooded river valley in Nottinghamshire, United Kingdom

Aedes vexans is known to occur in large populations in riverine floodplains in much of Europe, where it can cause a significant biting nuisance and is often subject to large scale control strategies. Until recently it had only been reported in very small numbers in the United Kingdom. After receiving reports of nuisance biting near the river Idle, Nottinghamshire (East Midlands, England), mosquito surveillance was conducted over three years (2018-2020) using Mosquito Magnet adult traps. Ae. vexans was found in all years, in very high numbers, particularly in 2020, reaching a peak of almost 5,000 female mosquitoes per trap night, the highest reported density of trapped adult mosquitoes in the UK. Larval control was conducted in all years, and adult control in one year, however local peculiarities of flood and water management presents challenges and necessitates a multi-faceted approach. Strategies for further expansion of the control operation by developing strategies for water management, coupled with larval surveys to define the extent and seasonality of larval habitats, and application methods of Bacillus thuringiensis israelensis products are discussed.

North America Insect Invades the World: the Case of the Flood Mosquito, Aedes vexans (Diptera: Culicidae), from Mitochondrial DNA

The flood mosquito, Aedes vexans (Diptera: Culicidae), native of Canada, and currently present in all continents, has a vector competence for 30 arboviruses, being responsible for transmitting diseases, like West Nile fever, Rift Valley fever, Saint Louis Encephalitis and Eastern Equine Encephalitis. Hence, knowing the structure and gene flow of A. vexans is important to develop adequate vector control strategies for this species. For this, from partial sequences of the mitochondrial COI gene available in Bold and GenBank, it was possible to determine the Haplotypic (Hd) and nucleotide (π) gene diversity, genetic structuring and gene flow at global, continental, and country levels. In total, 1184 sequences were recovered, distributed between America (88.60%), Europe (7.35%), Asia (3.89%), and Africa (0.17%). From these, 395 haplotypes (H) were detected without presence of pseudogenes (NUMTs), with H1 being the most frequent (24.58%) and between H12 - H395 the least frequent varying between 0.93% (H12) and 0.08% (H395). Phylogenetically, the haplotypes were grouped into six clades. Clade I grouped haplotypes from countries in America and Europe, while clades II and III presented haplotypes exclusively from Asia and Europe; clade IV grouped only one haplotype from Africa and the last ultimo clade V grouped haplotypes from America and Africa. The global Hd and π was 0.92 and 0.01, respectively. In addition, evidence was obtained of genetic structuring among continents (7.07%), countries (1.62%), and within countries (91.30%; FST = 0.08, p < 0.05) and no isolation by distance was detected (r = 0.003, p > 0.05). These results suggest that the mosquito populations that invaded other continents originate directly from the American continent, where possibly transcontinental commercial routes favored their long-distance dispersion.

Spot Survei Entomologi Malaria di Daerah Epidemi di Kabupaten Kotabaru Kalimantan Selatan

Latar belakang: Indonesia menargetkan eliminasi malaria pada tahun 2030. Kabupaten Kotabaru merupakan daerah endemis malaria. Salah satu Desa Endemis yaitu Desa Batang Kulur yang terjadi peningkatan kasus signifikan sebanyak 12 kasus pada Bulan Maret 2019. Tujuan penelitian ini adalah untuk mengukur indeks entomologi, karakteristik, dan lingkungan habitat perkembangbiakan vektor malaria di Desa Batang Kulur.Metode: Kegiatan yang dilakukan yaitu penangkapan nyamuk dengan umpan orang, identifikasi dan pembedahan ovarium nyamuk untuk diketahui parusitas (pernah/tidak pernah bertelur) yang digunakan untuk memprediksi umur dan survei habitat perkembangbiakan vektor malaria.Hasil: Spesies dan komposisi nyamuk yang ditemukan yaitu Aedes vexans, Aedes albopictus, Culex quinquefasciatus, Culex tritaeniorhynchus, Culex vishnui, Mansonia dives dan Anopheles leucosphyrus. Kepadatan nyamuk Anopheles leucosphyrus 0,30 dan kepadatan permalam yaitu 2,67 dengan peluang hidup perhari 95% serta perkiraan umur populasi 21,54 hari. Fluktuasi Anopheles leucosphyrus mulai muncul pada jam 22.00 dan kembali meningkat pada jam 04.00. Tempat perindukan nyamuk yang ditemukan yaitu Habitat perkembang biakan nyamuk yang ditemukan ada 2 yaitu kolam dan mata air.Simpulan: Terdapat habitat perkembang biakan yang mendukung, peluang hidup 95% dan potensi umur nyamuk lebih dari masa inkubasi Plasmodium sehingga di Desa Batang Kulur merupakan daerah yang cocok untuk perkembangan vektor malaria. ABSTRACT Title: Investigation of Spot Survey of Malaria Entomological in Epedemic Areas in Kotabaru District, South KalimantanBackground: Indonesia is targeting malaria elimination by 2030. Kotabaru Regency is a malaria endemic area. One of the endemic villages, Batang Kulur Village, saw a significant increase of 12 cases in March 2019. The purpose of this study was to measure the entomological index, characteristics, and environment of the malaria vector breeding habitat in Batang Kulur Village.Method: Activities carried out include catching mosquitoes by baiting people, telephone and surgery for the mosquito ovaries to determine of parity (parous /nullyparous) which are used to predict age and survey the breeding habitats for malaria vectors.Result: The mosquito species and composition found were Aedes vexans, Aedes albopictus, Culex quinquefasciatus, Culex tritaeniorhynchus, Culex vishnui, Mansonia dives and Anopheles leucosphyrus. The density of the Anopheles leucosphyrus was 0.30 and the per night density was 2.67 with a 95% chance of survival per day and an estimated population age of 21.54 days. Anopheles leucosphyrus fluctuations began to appear at 22.00 and again increased at 04.00. The mosquito breeding places found were 2 mosquito breeding habitats, namely ponds and springs.Conclusion: There is a suitable breeding habitat, a 95% chance of survival and a potential age of mosquitoes that is more than the plasmodium incubation period so that in Batang Kulur Village is a suitable area for the development of malaria vectors.

Monitoring Culicine Mosquitoes (Diptera: Culicidae) as a Vector of Flavivirus in Incheon Metropolitan City and Hwaseong-Si, Gyeonggi-Do, Korea, during 2019

The flaviviruses are small single-stranded RNA viruses that are typically transmitted by mosquitoes or tick vectors and are etiological agents of acute zoonotic infections. The viruses are found around the world and account for significant cases of human diseases. We investigated population of culicine mosquitoes in central region of Korean Peninsula, Incheon Metropolitan City and Hwaseong-si. Aedes vexans nipponii was the most frequently collected mosquitoes (56.5%), followed by Ochlerotatus dorsalis (23.6%), Anopheles spp. (10.9%), and Culex pipiens complex (5.9%). In rural regions of Hwaseong, Aedes vexans nipponii was the highest population (62.9%), followed by Ochlerotatus dorsalis (23.9%) and Anopheles spp. (12.0%). In another rural region of Incheon (habitat of migratory birds), Culex pipiens complex was the highest population (31.4%), followed by Ochlerotatus dorsalis (30.5%), and Aedes vexans vexans (27.5%). Culex pipiens complex was the predominant species in the urban region (84.7%). Culicine mosquitoes were identified at the species level, pooled up to 30 mosquitoes each, and tested for flaviviral RNA using the SYBR Green-based RT-PCR and confirmed by cDNA sequencing. Three of the assayed 2,683 pools (989 pools without Anopheles spp.) were positive for Culex flaviviruses, an insect-specific virus, from Culex pipiens pallens collected at the habitats for migratory birds in Incheon. The maximum likelihood estimation (the estimated number) for Culex pipiens pallens positive for Culex flavivirus was 25. Although viruses responsible for mosquito-borne diseases were not identified, we encourage intensified monitoring and long-term surveillance of both vector and viruses in the interest of global public health.

A novel negevirus isolated from Aedes vexans mosquitoes in Finland

Negeviruses are insect-specific enveloped RNA viruses that have been detected in mosquitoes and sandflies from various geographical locations. Here, we describe a new negevirus from Northern Europe, isolated from pool of Aedes vexans mosquitoes collected in Finland, designated as Mekrijärvi negevirus (MEJNV). MEJNV had a typical negevirus genome organization, is 9,740 nucleotides in length, and has a GC content of 47.53%. The MEJNV genome contains three ORFs, each containing the following identified conserved domains: ORF1 (7,068 nt) encodes a viral methyltransferase, an FtsJ-like methyltransferase, a viral RNA helicase, and an RNA-dependent RNA polymerase, ORF2 (1,242 nt) encodes a putative virion glycoprotein, and ORF3 (660 nt) encodes a putative virion membrane protein. A distinctive feature relative to other currently known negeviruses is a 7-nucleotide-long overlap between ORF1 and ORF2. MEJNV shares the highest sequence identity with Ying Kou virus from China, with 67.71% nucleotide and 75.19% and 59.00% amino acid sequence identity in ORF 1 and ORF 2, respectively. ORF3 had the highest amino acid sequence similarity to Daeseongdong virus 1 and negevirus Nona 1, both with 77.61% identity, and to Ying Kou virus, with 71.22% identity. MEJNV is currently the northernmost negevirus described. Our report supports the view that negeviruses are a globally distributed, diverse group of viruses that can be found from mosquitoes in a wide range of terrestrial biomes from tropical to boreal forests.

Identification and RNAi Profile of a Novel Iflavirus Infecting Senegalese Aedes vexans arabiensis Mosquitoes

The inland floodwater mosquito Aedes vexans (Meigen, 1830) is a competent vector of numerous arthropod-borne viruses such as Rift Valley fever virus (Phenuiviridae) and Zika virus (Flaviviridae). Aedes vexans spp. have widespread Afrotropical distribution and are common European cosmopolitan mosquitoes. We examined the virome of Ae. vexans arabiensis samples from Barkédji village, Senegal, with small RNA sequencing, bioinformatic analysis, and RT-PCR screening. We identified a novel 9494 nt iflavirus (Picornaviridae) designated here as Aedes vexans iflavirus (AvIFV). Annotation of the AvIFV genome reveals a 2782 amino acid polyprotein with iflavirus protein domain architecture and typical iflavirus 5’ internal ribosomal entry site and 3’ poly-A tail. Aedes vexans iflavirus is most closely related to a partial virus sequence from Venturia canescens (a parasitoid wasp) with 56.77% pairwise amino acid identity. Analysis of AvIFV-derived small RNAs suggests that AvIFV is targeted by the exogenous RNA interference pathway but not the PIWI-interacting RNA response, as ~60% of AvIFV reads corresponded to 21 nt Dicer-2 virus-derived small RNAs and the 24–29 nt AvIFV read population did not exhibit a “ping-pong” signature. The RT-PCR screens of archival and current (circa 2011–2020) Ae. vexans arabiensis laboratory samples and wild-caught mosquitoes from Barkédji suggest that AvIFV is ubiquitous in these mosquitoes. Further, we screened wild-caught European Ae. vexans samples from Germany, the United Kingdom, Italy, and Sweden, all of which tested negative for AvIFV RNA. This report provides insight into the diversity of commensal Aedes viruses and the host RNAi response towards iflaviruses.

Horizontal and Vertical Transmission of West Nile Virus by Aedes vexans (Diptera: Culicidae)

West Nile virus (family Flaviviridae, genus Flavivirus) first caused human and veterinary disease, and was isolated from Culex pipiens pipiens L. and Aedes vexans (Meigen) (Diptera: Culicidae) in the United States in 1999. We report that a Connecticut strain of Ae. vexans was competent to transmit West Nile virus both horizontally to suckling mice and vertically to its progeny in the laboratory. Horizontal transmission was first observed on day 6 post-exposure (pe). Daily horizontal transmission rates generally increased with the day post-virus exposure with highest rates of 67–100% recorded on days 28–30 pe. One female vertically transmitted West Nile virus on day 21 pe, but only after it had taken its third bloodmeal. Horizontal and vertical transmission may contribute to West Nile virus infection rates in Ae. vexans in summer, and vertical transmission provides a means of survival of West Nile virus during winter.