Belgian Culex pipiens pipiens are competent vectors for West Nile virus while Culex modestus are competent vectors for Usutu virus

Alina Soto; Lander De Coninck; Ann-Sophie Devlies; Celine Van De Wiele; Ana Lucia Rosales Rosas; Lanjiao Wang; Jelle Matthijnssens; Leen Delang

doi:10.1371/journal.pntd.0011649

Belgian Culex pipiens pipiens are competent vectors for West Nile virus while Culex modestus are competent vectors for Usutu virus

PLoS Negl Trop Dis. 2023 Sep 20;17(9):e0011649. doi: 10.1371/journal.pntd.0011649. eCollection 2023 Sep.

Authors

Alina Soto¹, Lander De Coninck², Ann-Sophie Devlies¹, Celine Van De Wiele¹, Ana Lucia Rosales Rosas¹, Lanjiao Wang¹, Jelle Matthijnssens², Leen Delang¹

Affiliations

¹ Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven, Leuven, Belgium.
² Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Clinical and Epidemiological Virology, KU Leuven, Leuven, Belgium.

Abstract

Background: West Nile virus (WNV) and Usutu virus (USUV) are emerging arthropod-borne viruses (arboviruses) in Europe transmitted by Culex mosquitoes. In Belgium, it is currently unknown which Culex species are competent vectors for WNV or USUV and if these mosquitoes carry Wolbachia, an endosymbiotic bacterium that can block arbovirus transmission. The aims of our study were to measure the vector competence of Belgian Culex mosquitoes to WNV and USUV and determine if a naturally acquired Wolbachia infection can influence virus transmission.

Methodology/principal findings: Female Culex mosquitoes were captured from urban and peri-urban sites in Leuven, Belgium and offered an infectious bloodmeal containing WNV lineage 2, USUV European (EU) lineage 3, or USUV African (AF) lineage 3. Blood-fed females were incubated for 14 days at 25°C after which the body, head, and saliva were collected to measure infection, dissemination, and transmission rates as well as transmission efficiency. Mosquito species were identified by qRT-PCR or Sanger sequencing, the presence of infectious virus in mosquitoes was confirmed by plaque assays, and viral genome copies were quantified by qRT-PCR. Culex pipiens pipiens were able to transmit WNV (4.3% transmission efficiency, n = 2/47) but not USUV (EU lineage: n = 0/56; AF lineage: n = 0/37). In contrast, Culex modestus were able to transmit USUV (AF lineage: 20% transmission efficiency, n = 1/5) but not WNV (n = 0/6). We found that the presence or absence of Wolbachia was species-dependent and did not associate with virus transmission.

Conclusions/significance: This is the first report that Belgian Culex mosquitoes can transmit both WNV and USUV, forewarning the risk of human transmission. More research is needed to understand the potential influence of Wolbachia on arbovirus transmission in Culex modestus mosquitoes.

Copyright: © 2023 Soto et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Arboviruses*
Belgium
Culex*
Culicidae*
Female
Flavivirus* / genetics
Humans
Mosquito Vectors
West Nile Fever*
West Nile virus* / genetics

Supplementary concepts

Usutu virus

Grants and funding

Funding was awarded internally to LD and JM by KU Leuven (Grant ID: C14/20/108). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.