Genetic Variation for West Nile Virus Susceptibility in Culex Tritaeniorhynchus *

Abstract

Mutant and geographical strains of Culex tritaeniorhynchus were compared for West Nile (WN) virus susceptibility by feeding on a high-titered blood-virus suspension. Eleven strains also were selected from 2-21 generations for an increase and/or a reduction of oral susceptibility using 90% and 10% infective virus doses, respectively. Only one of the 20 strains tested, e ma, was significantly less susceptible than the control strain. In the selection experiments, none of the strains showed a consistent decrease in susceptibility, but the Changa Manga II (CM) strain showed a sustained increase in susceptibility from generations F11-F21 when selection was discontinued. Reciprocal cross-matings and back-crosses were set up between the selected CM strain and two of the morphological mutant strains, e ma and re e ae, carrying homozygous recessive markers. The resulting progeny were tested for susceptibility to WN virus infection and the ability to replicate virus to high-titers after infection. These results suggest that the trait of increased susceptibility is dominant over resistance. The enhanced ability of infected mosquitoes to replicate WN virus showed partial dominance. Both of these traits appear to be polyfactorial, and are apparently associated with more than one chromosome in Cx. tritaeniorhynchus.

Experimental and Natural Vertical Transmission of West Nile Virus by California <I>Culex</I> (Diptera: Culicidae) Mosquitoes

“…Because the efÞciency of vertical transmission can be inßuenced by viral strain, rearing temperature, mosquito species and strains, and number of gonotrophic cycles completed by infected females (Hayes et al 1984;Baqar et al 1993;Anderson et al 2008Anderson et al , 2012, testing Þrst-instar larvae for WNV from locations with active horizontal transmission in late summer and fall also may identify areas with high rates of vertical transmission (Fechter-Leggett et al 2012). This could be used as a surveillance tool to focus mosquito control efforts during summer and before virus ampliÞcation in spring.…”

Vector-Virus Interactions and Transmission Dynamics of West Nile Virus

“…Even modest increases in EIP will exponentially increase vectorial capacity independent of intrinsic transmissibility (competence), so temperature, viral genotype, and other factors altering the pace of viral infections in mosquitoes are likely to be of primary importance in governing activity. Vector competence for WNV also has been shown to vary among mosquito populations of the same species [46,55,56,57] with evidence of a genetic basis [58], and may vary seasonally [59]. Spatio-temporal variability in vector competence of Cx.…”

Phenotypic Variation among Culex pipiens Complex (Diptera: Culicidae) Populations from the Sacramento Valley, California: Horizontal and Vertical Transmission of West Nile Virus, Diapause Potential, Autogeny, and Host Selection

“…67 The frequency of vertical transmission also may be influenced by rearing temperature and mosquito species and strains. 67,[69][70][71] Host selection. Results from this study agreed with previous findings in the Sacramento Valley, documenting that Cx.…”