Genetic structure and vector competence for DENV-2 of Aedes albopictus (Diptera: Culicidae) populations in China

Abstract

Background: As a vector of over 20 arboviruses, Aedes albopictus has spread throughout the world mostly since the second half of the twentieth century, and it is now found on every continent except Antarctica. Approximately 50-100 million people are infected with dengue virus (DENV) transmitted by Aedes mosquitoes each year, leading to a heavy economic burden on both governments and individuals. Understanding the population genetics and vector competence of vector species is critical to effectively preventing and controlling vector-borne diseases. The aim of this study was to examine the genetic structure and vector competence for dengue virus type 2 (DENV-2) of Ae. albopictus populations across China and their relationship.Methods: From July to September in 2019, Ae. albopictus eggs were collected by using ovitraps in 8 localities across China and reared to adults in laboratory. The mitochondrial gene cytochrome c oxidase subunit 1 (cox1) were used to examine the patterns of genetic diversity and population structure among native Ae. albopictus populations. The vector competence was detected by quantitative analysis of DENV-2 virus titer in mosquito tissues (midguts, heads and salivary glands) through qRT-PCR. The correlation between population genetic indices and DENV-2 loads in the mosquitoes’ tissues was also examined.Results: A total of 20 haplotypes of mtDNA cytochrome c oxidase subunit 1 (cox1) were identified in the 120 specimens from the eight tested populations. The dominate haplotype H01 was detected in seven geographic populations of mainland China. Genetic parameters such as haplotype diversity (Hd), nucleotide diversity (π), and fixation index (FST) revealed the population diversity decreasing from south to north, and low population genetic differentiation. STRUCTURE analysis indicated that Ae. albopictus populations in southern China were clustered. In addition, The Mantel test indicated a positive correlation between genetic distance and geographical distance (R2 = 0.364, P = 0.003). We observed no correlation between population genetic indices of cox1 in Ae. albopictus populations and DENV-2 virus loads. However, the southern populations had the low DENV-2 virus loads generally.Conclusion: Conventional genetic markers such as cox1 may not reflect genetic differences in mosquitoes’ vector competence in different regions. The fact of lower DENV-2 loads in southern populations may be associated with the stable immunity system established in mosquitoes due to the long-term prevalence of dengue disease in these areas. The genetic structure and vector competence of Ae. albopictus populations in this study may have implications for understanding the epidemiology, prevention and control of vector-borne diseases.