Disease & Vector Studies III/Larval Control I
Disease & Vector Studies III/Larval Control I
As West Nile virus (WNV) infected naïve host populations and vectors in the United States (US) following its introduction into the country, WNV is thought to have mutated and new genotypes emerged until an equilibrium (endemicity) was established. Richland County, SC has become an annual hotspot of endemic WNV transmission, where human cases (and recently—deaths), positive mosquito pools, and positive birds are reported annually. Unfortunately, public health response is lacking in this county, as resources are severely limited. A 2022 survey among residents found no correlation between mosquito bites and traditional risk factors for WNV disease, suggesting alternative risk factors and/or biological aspects associated with contemporary transmission in this hotspot. To better understand this phenomenon, this study was initiated in May 2023. From June – November 2023, Culex quinquefasciatus mosquitoes were sampled and screened from the 6 highest risk communities in Richland County for presence of WNV, and environmental characteristics were collected. Additionally, pre- (June) and post-WNV season (November) blood spots to test for WNV IgG and IgM antibodies and seroconversion and a WNV knowledge survey were collected from 130 participants in the same neighborhoods. Univariate regression analyses examined WNV risk factors associated with seropositivity. Climate variables’ variance and neighborhood characteristics were analyzed for associations to Culex spp. presence and WNV positivity. Residents’ WNV combined seropositivity was 21.9%, significantly higher than the estimated state and national seroprevalence. Additionally, traditional WNV risk factors were not statistically associated with seropositivity. Culex quiquefasciatus mosquitoes were not collected ubiquitously throughout the high-risk neighborhoods, and a greater variance in climate variables was significantly associated with fewer Cx. quiquefasciatus mosquitoes collected. With these surprising results, next steps include investigating the lineage of WNV through next-generation sequencing. Has WNV lineage evolution over time led to novel transmission dynamics distinct from the original 1999 infecting lineage?