Abstract
A bite from a La Crosse virus (LACV) infected Aedes mosquito can cause La Crosse encephalitis (LACE), which is a neuro-invasive disease that disproportionately affects children under the age of 16 in Southern Appalachia. The three vectors for LACV are Aedes albopictus (Skuse), Ae. japonicus (Theobald), and Ae. triseriatus (Say). Localized maps of the geographic distribution of vectors are practical tools for mosquito management personnel to target areas with high mosquito abundance. This study hypothesized that LACV vectors have unique species-specific spatial and temporal clusters. To test this, 44 sites were identified in Knox County, Tennessee for their land use/type. At each site, host-seeking mosquitoes were collected approximately every other week from May-October 2018. Spatial clusters of host-seeking mosquito collections for each of the three mosquito species were investigated using Kulldorff’s spatial scan statistic, specifying a retrospective space-time Bernoulli model. Most vector clusters were identified in south-central Knox County while the seasonality of clusters varied by mosquito species. Clusters of Ae. albopictus were observed throughout the entire study period while clusters of Ae. japonicus and Ae. triseriatus only occurred May-June. The findings indicate that the relative abundance of LACV vectors were more abundant in south-central Knox County compared to the rest of the county. Of interest, these clusters spatially overlapped with previous LACE diagnosed cases. These findings are useful in guiding decisions on targeted mosquito control in Knox County and may be applied to other counties within Southern Appalachia.
Highlights
La Crosse virus (LACV) remains a persistent arboviral threat in the Southern Appalachian region of the United States (US) since pediatric encephalitis cases caused by this pathogen emerged in Southern Appalachia in the 1990s [1]
The densities of these mosquitoes often vary throughout the season with Ae. triseriatus populations emerging in May and peaking in June, while Ae. albopictus populations emerge in June and peak in August / September; Ae. japonicus populations are still poorly understood in Tennessee [16,17,18,19]
The density of Ae. albopictus to Ae. triseriatus mosquitoes in a single mixed-forested hardwood setting was described as 1.2:1 [16], and we reported varying densities at additional Knox county sites which included previously LACV-positive homes [18,19]
Summary
La Crosse virus (LACV) remains a persistent arboviral threat in the Southern Appalachian region of the United States (US) since pediatric encephalitis cases caused by this pathogen emerged in Southern Appalachia in the 1990s [1]. The density of Ae. albopictus to Ae. triseriatus mosquitoes in a single mixed-forested hardwood setting was described as 1.2:1 [16], and we reported varying densities at additional Knox county sites which included previously LACV-positive homes [18,19]. Combined, this indicates that the Aedes populations are heterogeneous across space and time making targeted control difficult without surveillance
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