Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven, Leuven, Belgium.
Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Clinical and Epidemiological Virology, KU Leuven, Leuven, Belgium.
PLoS Negl Trop Dis. 2023 Sep 20;17(9):e0011649. doi: 10.1371/journal.pntd.0011649. eCollection 2023 Sep.
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.
西尼罗河病毒（WNV）和乌苏图病毒（USUV）是欧洲新兴的虫媒病毒（arboviruses），由库蚊传播。在比利时，目前尚不清楚哪些库蚊种是 WNV 或 USUV 的有效传播媒介，以及这些蚊子是否携带沃尔巴克氏体（一种可以阻断 arbovirus 传播的内共生细菌）。我们的研究旨在测量比利时库蚊对 WNV 和 USUV 的媒介效能，并确定是否自然获得的沃尔巴克氏体感染会影响病毒传播。
方法/主要发现：从比利时鲁汶的城市和城郊地区捕获了雌性库蚊，并提供了含有 WNV 谱系 2、USUV 欧洲（EU）谱系 3 或 USUV 非洲（AF）谱系 3 的感染性血餐。血餐后，将雌性蚊子在 25°C 下孵育 14 天，然后收集身体、头部和唾液，以测量感染、传播和传播率以及传播效率。通过 qRT-PCR 或 Sanger 测序鉴定蚊子种类，通过噬斑测定法确认蚊子中是否存在传染性病毒，并用 qRT-PCR 定量病毒基因组拷贝数。发现库蚊能够传播 WNV（4.3%的传播效率，n = 2/47），但不能传播 USUV（EU 谱系：n = 0/56；AF 谱系：n = 0/37）。相比之下，库蚊能够传播 USUV（AF 谱系：20%的传播效率，n = 1/5），但不能传播 WNV（n = 0/6）。我们发现沃尔巴克氏体的存在与否与病毒传播无关，且与蚊种有关。
结论/意义：这是比利时库蚊能够传播 WNV 和 USUV 的首次报道，警告了人类传播的风险。需要更多的研究来了解沃尔巴克氏体对库蚊中 arbovirus 传播的潜在影响。
