Bouckaert, J. | bioRxiv Science

bioRxiv2022

First report of kdr L1014F and ace-1 G119S insecticide resistance in Belgian Culex mosquitoes

The emergence of West Nile virus and Usutu virus in Europe poses a significant risk to public health. In the absence of efficient antiviral therapy or vaccine candidates, the only strategy to control these arboviruses is to target the Culex (Diptera: Culicidae) mosquito vector. However, the selection pressure caused by exposure to insecticides for vector control or agricultural pest control can lead to insecticide resistance, thereby reducing the efficacy of insecticide-based vector control interventions. In Culex mosquitoes, two of the most common amino acid substitutions associated with insecticide resistance are the kdr L1014F in voltage gated sodium channels and G119S in acetylcholinesterase. In this study, Culex pipiens biotype pipiens, Culex torrentium, and Culex modestus were sampled from 2019 to 2021 in three distinct environmental habitats (urban, peri-urban, and agricultural) in and around the city of Leuven, Belgium. Individual mosquitoes were screened for two mutations resulting in L1014F and G119S amino acid substitutions. Both mutations were observed in Culex pipiens and Culex modestus but not in Culex torrentium mosquitoes across the four collection sites. Furthermore, multi-resistance or cross-resistance in Culex pipiens could be a threat in these areas, as both mutations were observed at low frequencies. These results provide the first report of kdr L1014F and ace-1 G119S resistance in Culex pipiens and Culex modestus mosquitoes from Belgium, highlighting the importance of mosquito surveillance to design effective arbovirus outbreak control strategies.

molecular biology↗

bioRxiv2020

Establishment of Culex modestus in Belgium and a glance into the virome of Belgian mosquito species

Culex modestus mosquitoes are known transmission vectors of West Nile virus and Usutu virus. Their presence has been reported across several European countries, including only one larva confirmed in Belgium in 2018. Mosquitoes were collected in the city of Leuven and surroundings in the summer of 2019 and 2020. Species identification was performed based on morphological features and partial sequences of the mitochondrial cytochrome oxidase subunit 1 (COI) gene. The 107 mosquitoes collected in 2019 belonged to eight mosquito species: Cx. pipiens (24.3%), Cx. modestus (48.6%), Cx. torrentium (0.9%), Culiseta annulata (0.9%), Culiseta morsitans (0.9%), Ae. sticticus (14.0%), Ae. cinereus (9.3%) and Anopheles plumbeus (0.9%), suggesting the presence of an established Cx. modestus population in Belgium. Collection of Cx. modestus mosquitoes at the same locations in 2020, confirmed the establishment in the region. Haplotype network analysis of the COI sequences for Cx. modestus showed that the Belgian population is rather diverse, suggesting that it may have been established in Belgium for some time. The Belgian Cx. modestus population was most closely related to populations from the UK and Germany. Characterization of the virome of the collected mosquitoes resulted in the identification of at least 33 eukaryotic viral species. Nine (near-) complete genomes belonging to 6 viral species were identified, all of which were closely related to known viruses. In conclusion, we here report the presence of Cx. modestus in the surroundings of Leuven, Belgium. As this species is known to be a vector of several arboviruses, the implementation of vector surveillance programs monitoring this species is recommended. ImportanceCulex modestus is a mosquito species that plays a role as a bridge vector, being able to transmit pathogens between birds, as well as from birds to mammals, including humans. In Belgium, this mosquito species was considered absent, until the finding of one larva in 2018 and subsequent evidence of a large population in 2019-2020 described here. We collected mosquitoes in the summer of 2019 and 2020 in the city of Leuven and surroundings. The mosquito species was identified by morphological and molecular methods, demonstrating the presence of Cx. modestus in this region. The ability of mosquitoes to transmit pathogens can depend on several factors, one of them being their natural virus composition. Therefore, we identified the mosquito-specific viruses harboured by Belgian mosquitoes. As Cx. modestus is able to transmit viruses such as West Nile virus and Usutu virus, the establishment of this mosquito species may increase the risk of virus transmission in the region. It is thus advisable to implement mosquito surveillance programs monitoring this species.

microbiology↗