First report of <i>Culex flavivirus</i> and its association with <i>Wolbachia</i> in <i>Culex quinquefasciatus</i> from Puducherry, India

BACKGROUND: Symbiotic insect-specific viruses, such as Culex flavivirus (CxFV), are increasingly recognized for their ability to modulate arboviral replication in mosquitoes. However, the prevalence of CxFV in Culex quinquefasciatus mosquitoes from Puducherry, India-a region previously endemic for filariasis-and its interaction with the endosymbiotic bacterium Wolbachia pipientis, remain unexplored. METHODS: Culex quinquefasciatus mosquitoes were collected from villages in and around Puducherry. A total of 150 pools were screened for CxFV by PCR targeting the NS-5 gene and the amplicons were sequenced. Further, 100 individual mosquitoes were tested for both CxFV and the relative density of Wolbachia. RESULTS: The study identified a CxFV prevalence of 3.73% (95% CI 2.27-5.46) among the mosquito pools by Bayesian estimation approach. Phylogenetic analysis classified the circulating strain as genotype 2 of CxFV. The median relative density of Wolbachia was observed to be 0.170 (IQR 0.009-0.683) in CxFV-positive mosquitoes and 0.132 (IQR 0.021-0.570) in CxFV-negative mosquitoes, with no statistically significant difference between the two groups. CONCLUSIONS: Thus, with the first report on the circulation of CxFV-infected mosquitoes in Puducherry, the study highlights a probable lack of association between the relative density of Wolbachia and CxFV. ACCESSION NUMBERS: The raw sequence reads have been deposited in GenBank (https://www.ncbi.nlm.nih.gov/nuccore/) with the following accession numbers: PQ586414, PQ586415, PQ586416, PQ586417, PQ586418, PQ586419, PQ586420, PQ586421, PQ586422, PQ586423.