Spatiotemporal Co-occurrence of Flanders and West Nile Viruses WithinCulexPopulations in Shelby County, Tennessee

Abstract

West Nile virus (WNV) and Flanders virus (FLAV) can cocirculate in Culex mosquitoes in parts of North America. A large dataset of mosquito pools tested for WNV and FLAV was queried to understand the spatiotemporal relationship between these two viruses in Shelby County, TN. We found strong evidence of global clustering (i.e., spatial autocorrelation) and overlapping of local clustering (i.e., Hot Spots based on Getis Ord Gi*) of maximum likelihood estimates (MLE) of infection rates (IR) during 2008-2013. Temporally, FLAV emerges and peaks on average 10.2 wk prior to WNV based on IR. Higher levels of WNV IR were detected within 3,000 m of FLAV-positive pool buffers than outside these buffers.

Co-circulation of Flanders Virus and West Nile Virus in Culex Mosquitoes (Diptera: Culicidae) from Chicago, Illinois

“…The prototype strain 61-7684 was first isolated in the town of Flanders in Long Island, NY in 1961 ( Whitney 1964 ). FLAV is widely distributed throughout the United States and circulates in a bird-mosquito cycle in the eastern half of the United States ( Whitney 1964 ; Mack et al 1967 ; Sudia et al 1967a ; Sudia et al 1967b ; Chamberlain et al 1969 ; Kokernot et al 1969 ; Kokernot et al 1974 ; Main et al 1979 ; Rowley et al 1983 ; Andre et al 1985 ; Gilliland et al 1995 ; Mitchell et al 1996 ; Nasci et al 2001 ; Wozniak et al 2001 ; Takeda et al 2003 ; Lucero et al 2016 ), Utah ( Crane et al 1970 ), Canada ( Hall et al 1969 ; Thorsen et al 1980 ; Belloncik et al 1982 ), and Mexico ( Sudia et al 1975 ).…”

“…Similar to West Nile virus (WNV), avian hosts involved in transmission include house sparrows ( Passer domesticus L., Passeriformes: Passeridae), red-winged blackbirds ( Agelaius phoeniceus L., Passeriformes: Icteridae), and Northern cardinals ( Cardinalis cardinalis L., Passeriformes: Cardinalidae) ( Whitney 1964 ; Kokernot et al 1969 ) and common mosquito vectors belong to the Culex genus (Diptera: Culicidae) (e.g., Culex quinquefasciatus Say, Culex pipiens L., Culex restuans Theobald, and Culex tarsalis Coquillett), all of which vector zoonotic encephalitic viruses ( Sudia et al 1967b ; Kokernot et al 1969 ; Nasci et al 2001 ). In contrast to WNV, FLAV is not known to be pathogenic in humans ( Kokernot et al 1969 ; Lucero et al 2016 ).…”

“…Because FLAV and WNV share the same hosts and vectors, there is renewed interest in patterns of FLAV and WNV co-occurrence in space and time. According to Lucero et al (2016) , FLAV circulates between April and October with a peak in June, approximately 10 wk prior to the peak of WNV in Tennessee. Spatially, WNV occurred within 3,000 m (1.86 miles) of FLAV-positive pools in Shelby County, Tennessee, with positive locations overlapping geographically during peak transmission ( Lucero et al 2016 ).…”

“…According to Lucero et al (2016) , FLAV circulates between April and October with a peak in June, approximately 10 wk prior to the peak of WNV in Tennessee. Spatially, WNV occurred within 3,000 m (1.86 miles) of FLAV-positive pools in Shelby County, Tennessee, with positive locations overlapping geographically during peak transmission ( Lucero et al 2016 ). FLAV may therefore serve as an ‘early warning system’ for WNV amplification ( Lucero et al 2016 ).…”

“…Spatially, WNV occurred within 3,000 m (1.86 miles) of FLAV-positive pools in Shelby County, Tennessee, with positive locations overlapping geographically during peak transmission ( Lucero et al 2016 ). FLAV may therefore serve as an ‘early warning system’ for WNV amplification ( Lucero et al 2016 ).…”