Epidemic West Nile Virus Infection Rates and Endemic Population Dynamics Among South Dakota Mosquitoes: A 15-yr Study from the United States Northern Great Plains

Abstract

Mosquito surveillance has been conducted across South Dakota (SD) to record and track potential West Nile virus (WNV) vectors since 2004. During this time, communities from 29 counties collected nearly 5.5 million mosquitoes, providing data from over 60,000 unique trapping nights. The nuisance mosquito, Aedes vexans (Meigen) was the most abundant species in the state (39.9%), and most abundant in most regions. The WNV vector, Culex tarsalis Coquillett (Diptera: Culicidae), was the second most abundant species (20.5%), and 26 times more abundant than the other Culex species that also transmit WNV. However, geographic variation did exist between WNV vector species, as well as relative abundance of vector and nuisance mosquitoes. The abundance of Ae. vexans decreased from east to west in South Dakota, resulting in an increase in the relative abundance of Cx. tarsalis. Other species are reported in this study, with various relative abundances throughout the different regions of South Dakota. WNV infection rates of mosquitoes showed that Cx. tarsalis had the most positive sampling pools and the highest vector index of all the species tested. This study addressed the need for an updated summary of the predominant mosquito species present in the United States Northern Great Plain and provides infection rate data for WNV among these predominant species.

Integrated Forecasts Based on Public Health Surveillance and Meteorological Data Predict West Nile Virus in a High-Risk Region of North America

“…However, high mosquito abundances and frequent bites do not necessarily translate into high risk of WNV transmission. In South Dakota, the most important nuisance mosquito is Aedes vexans , which occurs in large numbers in spring and early summer after heavy rains flood their breeding habitats ( Vincent et al. 2020 ).…”

“…We chose this approach because it was relatively insensitive to changes in the numbers and locations of mosquito traps from year to year, allowing us to use all of our statewide mosquito data for model calibration and prediction. A prior study found that, in South Dakota, mosquito abundance is not a strong indicator of human WNV risk ( Vincent et al. 2020 ).…”

“…Culex tarsalis has been implicated as the primary mosquito vector of WNV in South Dakota and surrounding states ( Dunphy et al. 2019 ; Vincent et al. 2020 ).…”

A panel of real-time PCR assays for the detection of Bourbon virus, Heartland virus, West Nile virus, and Trypanosoma cruzi in major disease–transmitting vectors

“…1 This assay has been used in the detection or surveillance of WNV in people, mosquitoes, birds, or horses. 14,30,34 To meet the need for simultaneous testing of multiple pathogens, we modified the assay protocol and validated the assay, which showed excellent sensitivity and specificity. A study using the primers/probe set detected as few as 10 The same primers/probe set also showed high sensitivity in our study, with a detection limit of 10 copies per reaction, and the sensitivity was not affected by the vector background.…”

“…1 This assay has been used in the detection or surveillance of WNV in people, mosquitoes, birds, or horses. 14,30,34 To meet the need for simultaneous testing of multiple pathogens, we modified the assay protocol and validated the assay, which showed excellent sensitivity and specificity. A study using the primers/probe set detected as few as 10 1.7–2.3 pfu of WNV/mL in infected mosquitoes, C. pipiens quinquefasciatus.…”