Culex Flavivirus and West Nile Virus inCulex quinquefasciatusPopulations in the Southeastern United States

Abstract

Little is known of the interactions between insect-only flaviviruses and other arboviruses in their mosquito hosts, or the potential public health significance of these associations. The specific aims of this study were to describe the geographic distribution, prevalence, and seasonal infection rates of Culex flavivirus (CxFV) and West Nile virus (WNV) in Culex quinquefasciatus Say in the Southeastern United States, investigate the potential association between CxFV and WNV prevalence in Cx. quinquefasciatus and describe the phylogenetic relationship among CxFV and WNV isolates from the Southeastern United States and around the world. Using ArboNET records, 11 locations were selected across Georgia, Mississippi, and Louisiana that represented a range of WNV human case incidence levels. Cx. quinquefasciatus were trapped weekly throughout the summer of 2009 and pools were screened for flavivirus RNA by reverse transcriptase polymerase chain reaction. Cx. quinquefasciatus from Georgia had significantly higher CxFV infection rates than either Mississippi or Louisiana. CxFV was not detected in Mississippi after July, and no CxFV was detected in Cx. quinquefasciatus in Louisiana. In Georgia, CxFV infection rates were variable between and within counties and over time. WNV infection rates were not significantly different across states or months, and WNV sequences from all three states were identical to each other in the envelope and NS5 gene regions. Phylogenetically, NS5 and E gene sequences from Georgia CxFV isolates clustered with CxFV from Japan, Iowa, and Texas. Multiple CxFV genetic variants were found circulating simultaneously in Georgia. No evidence was found supporting an association between WNV and CxFV infection prevalence in Cx. quinquefasciatus.

Insect-Specific Viruses Detected in Laboratory Mosquito Colonies and Their Potential Implications for Experiments Evaluating Arbovirus Vector Competence

“…A field study conducted in Chicago found a positive ecological association between the infection rates with WNV and CxFV, in Culex pipiens mosquito pools. 41 In contrast, Crockett and others 42 found no evidence to support an association between WNV and CxFV prevalence rates in Culex quinquefasciatus populations in the southeastern United States. In vitro and in vivo studies looking at the potential interaction of WNV with insect-specific flaviviruses in mosquito cells and in mosquitoes have also produced conflicting results.…”

Insect-Specific Viruses

“…collected in the field (Newman et al, 2011). However, a study conducted in the southern United States found no such correlation (Crockett et al, 2012). Several arboviruses, including WNV (Bolling et al, 2012;Hobson-Peters et al, 2013;Kenney et al, 2014;Kent et al, 2010), Murray Valley encephalitis virus (Hobson-Peters et al, 2013), Japanese encephalitis virus (Kenney et al, 2014), and St. Louis encephalitis virus (Kenney et al, 2014), have been shown to exhibit inhibited replication in the C6/36 mosquito cell line when preinfected or coinfected with ISVs.…”

Wide detection of Aedes flavivirus in north-eastern Italy – a European hotspot of emerging mosquito-borne diseases

“…However, evidence of super-infection exclusion has not always been reported in cases of viral co-infections. For example, Kent et al (2010) found that CxFV Izabal strain did not affect the vector competence of Culex quinquefasciatus for transmitting WNV when mosquitoes were infected sequentially in the laboratory, and Crockett et al (2012) found no evidence supporting an association between WNV and CxFV infection prevalence in wild mosquitoes.…”