First Detection of West Nile Virus Lineage 2 in Mosquitoes in Switzerland, 2022

West Nile virus (WNV) is one of the most widespread flaviviruses in the world, and in recent years, it has been frequently present in many Mediterranean and Eastern European countries. A combination of different conditions, such as a favourable climate and higher seasonal average temperatures, proba...

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Bibliographic Details
Published in:Pathogens (Basel) 2023-12, Vol.12 (12), p.1424
Main Authors: Cazzin, Stefania, Liechti, Nicole, Jandrasits, Damian, Flacio, Eleonora, Beuret, Christian, Engler, Olivier, Guidi, Valeria
Format: Article
Language:English
Subjects:
Aquatic insects
arbovirus surveillance
Birds
Cards
Climate
Culex pipiens
Disease transmission
Distribution
Encephalitis
Gene sequencing
Genetic aspects
Genomes
Health aspects
honey-baited FTA cards
Horses
Identification and classification
Mosquitoes
Phylogenetics
Physiological aspects
Risk factors
Surveillance
Thermal cycling
Vector-borne diseases
Vectors
Viruses
West Nile fever
West Nile virus
Whole genome sequencing
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Summary:West Nile virus (WNV) is one of the most widespread flaviviruses in the world, and in recent years, it has been frequently present in many Mediterranean and Eastern European countries. A combination of different conditions, such as a favourable climate and higher seasonal average temperatures, probably allowed its introduction and spread to new territories. In Switzerland, autochthonous cases of WNV have never been reported, and the virus was not detected in mosquito vectors until 2022, despite an entomological surveillance in place in Canton Ticino, southern Switzerland, since 2010. In 2022, 12 sites were monitored from July to October, using BOX gravid mosquito traps coupled with honey-baited FTA cards. For the first time, we could detect the presence of WNV in FTA cards and mosquitoes in 8 out of the 12 sampling sites monitored, indicating an unexpectedly widespread circulation of the virus throughout the territory. Positive findings were recorded from the beginning of August until mid-October 2022, and whole genome sequencing analysis identified a lineage 2 virus closely related to strains circulating in Northern Italy. The entomological surveillance has proved useful in identifying viral circulation in advance of possible cases of WNV infection in humans or horses.
ISSN:2076-0817
2076-0817
DOI:10.3390/pathogens12121424