Establishment ofCulex modestusin Belgium and a glance into the virome of Belgian mosquito species

Abstract

Culex modestus is a mosquito species with a relevant role in the transmission of West Nile virus and Usutu virus. Its presence has been reported across Europe, yet it is absent in Belgium. Field mosquitoes in the city of Leuven and surroundings were collected in the summer of 2019 and 2020. Species identification was performed by morphological features and partial sequences of the mitochondrial cytochrome oxidase subunit 1 (COI) gene. In order to examine the genetic structure of the Cx. modestus population found in Leuven, mitochondrial sequences of Cx. modestus mosquitoes collected in other 8 countries across Europe were retrieved from GenBank and confronted to the COI sequences from Belgian mosquitoes to construct a haplotype network.Hereby, we confirmed the new establishment of Cx. modestus in the surroundings of Leuven, Belgium. Haplotype network analysis showed that the Belgian population is rather diverse, suggesting that it must have been establish in Belgium for some time. The Belgian population was most closely related to Cx. modestus populations from the UK and Germany. The NetoVIR protocol was used to study the virome of 8 pools of mosquitoes. At least 33 eukaryotic viral species were identified. Nine (near-)complete genomes belonging to 6 viral species were identified, named Culex totivirus Leu1, Leu2 and Leu3, Alphamesonivirus Leu4, Iflavirus Leu5 and Leu6, Negevirus Leu7 and Leu8, and Rhabdovirus Leu9, all of which were closely related to known viruses. In conclusion, with the introduction of Cx. modestus in Belgium, the evaluation of its potential role in the transmission of arboviruses that could cause disease in animals and humans is necessary.Importance for non-specialistCulex modestus is a mosquito species that plays a role in nature as a ‘bridge’ vector, being able to transmit pathogens between birds, as well as from birds to mammals, including humans. In Belgium, this species was considered absent. Field mosquitoes were collected in urban, peri-urban and wetland areas in the summer of 2019 and 2020 in Leuven, and morphological and molecular methods were performed to confirm the presence of Cx. modestus in this region. The ability of mosquitoes to transmit pathogens can depend on a lot of factors, one of them being the natural virus composition in their bodies. For this purpose, we aimed to identify the whole virus group harbored by Belgian mosquitoes. This could provide more insight for mosquito and, therefore, disease control. Besides, the introduction of Cx. modestus may increase the risk of disease transmission. It is advisable to implement mosquito surveillance programs monitoring this species.

Intrinsic variation in the vertically transmitted core virome of the mosquito Aedes aegypti

“…This virus showed striking similarity to Aedes aegypti toti‐like viruses from Guadaloupe and an unnamed virus identified in A. aegypti from Thailand. Totiviridae and toti‐like viruses have been found in several mosquito genera with widespread global prevalence, including Anopheles in Liberia (Fauver et al, 2016), Armigeres in China (Zhai et al, 2010), Culex in Belgium (Wang et al, 2020), Culex in California (Batson et al, 2021), Culex in Australia (Williams et al, 2020), Culex in Japan (Isawa et al, 2011), and Mansonia in Brazil (de Lara Pinto et al, 2017), suggesting that toti‐like viruses may be common components of core viromes among mosquito populations. Metagenomic analyses of mosquitoes from our Palmetto site collected in 2016 and 2017 also identified a toti‐like virus, as well as dsRNA virus environmental sample (Boyles et al, 2020), further supporting that A. aegypti mosquitoes with similar genetic backgrounds (here, representative of central Florida‐based populations) share many of the same viruses, as previously reported (Konstantinidis et al, 2021; Öhlund et al, 2019; Shi et al, 2019; Wang et al, 2020).…”

“…Similarly, the Partitiviridae and partiti‐like viruses have been historically associated with plants and fungi (Nibert et al, 2014), and their associations with arthropods have only recently been discovered, largely from high‐throughput sequencing data. Partitiviridae and partiti‐like viruses have been reported across numerous mosquito genera ( Culex , Culiseta , Coquilettidia , Anopheles , Aedes ) with a nearly global distribution (North and South America, Africa, Asia, and Europe) (Konstantinidis et al, 2021; Öhlund et al, 2019; Shi et al, 2019; Wang et al, 2020). The low congruence between viral host phylogeny and host‐range for these partiti‐like viruses may suggest a recent host‐switching event (Dolja & Koonin, 2018; Grubaugh et al, 2016), as the Palmetto partiti‐like virus was highly divergent (<80% similarity) from other known partiti‐like viruses and probably represents a novel virus.…”

“…The clear mosquito‐associated clade present in the toti‐virus like sequences (Figures 4 and 5) could represent widespread concurrent viral movement or long host coevolution (Wang et al, 2020), as is thought to be the case for Bunyaviridae, Flaviviridae, Rhabdoviridae, and Togoviridae ISVs, which are assumed to have evolved and diversified alongside their host (Vasilakis & Tesh, 2015). Historically, totiviruses were primarily fungal associated, and probably represent a viral taxon with an ancient origin (Dolja & Koonin, 2018).…”

First report of kdr L1014F and ace-1 G119S insecticide resistance in Belgian Culex (Diptera: Culicidae) mosquitoes

“…Culex modestus and Culex torrentium mosquitoes were identified morphologically using the key of Becker 21 and then by COX1 Sanger sequencing. 22…”

“…[15][16][17] Native mosquito species in Belgium include members of the Culex pipiens species complex (Culex pipiens biotype pipiens and Culex pipiens biotype molestus), Culex torrentium, and Culex modestus. 18,19 To date, there is no information regarding the presence of insecticide resistance in mosquito species from Belgium or neighbouring countries. In this study, we investigated the presence of two common insecticide resistance mechanisms, kdr L1014F and ace-1 G119S, in Culex pipiens biotype pipiens, Culex torrentium, and Culex modestus mosquitoes from Belgium.…”