BackgroundUnderstanding mechanisms that contribute to viral dissemination in mosquito vectors will contribute to our ability to interfere with the transmission of viral pathogens that impact public health. The expression of genes in two Culex pipiens quinquefasciatus populations from Florida with known differences in vector competence to West Nile virus (WNV) were compared using high throughput sequencing.ResultsA total of 15,176 transcripts were combined for comparison of expression differences between the two populations and 118 transcripts were differentially expressed (p < 0.05). The fold change in expression of the differentially expressed genes ranged from -7.5 – 6.13. The more competent population for WNV (Gainesville) over expressed 77 genes and down regulated 44 genes, compared with the less competent population for WNV (Vero Beach). Also, splicing analysis identified 3 transcripts with significantly different splice forms between the two populations. The functional analysis showed that the largest proportion of transcripts was included in the catalytic activity and transporter activity groups except for those in the unknown group. Interestingly, the up- regulated gene set contained most of the catalytic activity function and the down- regulated gene set had a notable proportion of transcripts with transporter activity function. Immune response category was shown in only the down regulated gene set, although those represent a relatively small portion of the function. Several different vitellogenin genes were expressed differentially. Based on the RNAseq data analysis, ovary development was compared across the populations and following WNV infection. There were significant differences among the compared groups.ConclusionsThis study suggests that ovary development is correlated to vector competence in two Culex populations in Florida. Both populations control energy allocations to reproduction as a response to WNV. This result provides novel insight into the defense mechanism used by Culex spp. mosquitoes against WNV.

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Mayaro virus is a mosquito-borne Alphavirus endemic to forests of tropical South America with a sylvatic cycle involving non-human primates and Haemagogus mosquitoes. Human infection with Mayaro virus causes a febrile illness and long-lasting arthralgia and cases are often associated with exposure to tropical forest habitats. Human movement between tropical forest habitats and urban settings may allow for imported cases and subsequent local transmission by domestic mosquito Aedes aegypti. The relative importance of Ae. aegypti as a vector of Mayaro virus may depend on the pathogenic effects of the virus on fitness correlates, especially those entomological parameters that relate to vectorial capacity. We performed mosquito infection studies and compared adult survival and fecundity of females from Brazilian and Floridian populations of Ae. aegypti following oral ingestion of uninfectious (control) and Mayaro virus infectious blood. Mayaro virus infected and refractory mosquitoes had similar or 30–50% lower fecundity than control (unexposed) mosquitoes, suggesting a reproductive cost to mounting an immune response or phenotypic expression of refractoriness. Survival of adult female mosquitoes and targeted gene expression in the Toll and IMD pathways were not altered by Mayaro virus infection. Adult lifespan and fecundity estimates were independent of measured viral titer in the bodies of mosquitoes. The lack of adverse effects of infection status on female survival suggests that Mayaro virus will not alter vectorial capacity mediated by changes in this parameter.