Abstract
Aedes albopictus is a vector of over 20 arboviruses that has spread throughout the world, mainly in the second half of the twentieth century. Approximately 50–100 million people are infected with dengue virus (DENV) transmitted by Aedes mosquitoes each year, leading to heavy economic burdens for both governments and individuals, among countless other negative consequences. Understanding the vector competence of vector species is critical for effectively preventing and controlling vector-borne diseases. Accordingly, in this study, vector competence was evaluated by quantitative analysis of DENV-2 loads in mosquito tissues (midguts, heads, and salivary glands) and whole mosquitoes through real-time quantitative polymerase chain reaction (RT-qPCR) analysis. Wolbachia and the expression of immune-associated genes (Rel1, Rel2, Dicer2, and STAT) in mosquitoes were also detected by RT-qPCR to explore their impact on vector competence. The amount of DENV-2 in the mosquito midguts, heads, and salivary glands from southern-western China were found to be lower than those from eastern-central-northern China. The DENV-2 loads in whole mosquitoes showed a negative correlation with Rel1 gene (r = -0.285, P = 0.011) and STAT gene expression levels (r = -0.289, P = 0.009). In terms of Wolbachia strains, the density of the wAlbB strain was found to be significantly higher than that of the wAlbA strain in the eight Ae. albopictus populations, and the relative density of the wAlbB strain in mosquitoes from southern-western China was higher than those from eastern-central-northern China. The relative density of the wAlbB strain showed a negative correlation with the mean loads of DENV-2 in the heads (r = -0.729, P = 0.040), salivary glands (r = -0.785, P = 0.021), and whole mosquitoes (r = -0.909, P = 0.002). Thus, there are lower DENV-2 loads in the mosquitoes from southern-western China, which may be related to the innate immunity of mosquitoes as affected by Rel1 in the Toll pathway, STAT in the JAK-STAT pathway, and the relative density of the wAlbB strain.
Highlights
Aedes (Stegomyia) albopictus (Skuse, 1894) is an anthropophilic mosquito that originated in Southeast Asia and has spread to many countries across all continents except Antarctica (Goubert et al, 2016)
The present study is a continuation of that work that aims to address the following questions: (i) What are the vector competences for dengue virus (DENV)-2 of different geographic strains of Ae. albopictus populations in China? (ii) Is susceptibility to DENV-2 affected by Wolbachia and immune-associated genes in Ae. albopictus populations? The data gained from this study provides useful information for understanding the epidemiology, prevention, and control of vector-borne diseases
The DENV-2 loads in whole mosquitoes, heads, and salivary glands show a negative correlation with the relative density of wAlbB Wolbachia. These results indicate that the density of wAlbB Wolbachia may have changed due to the influence of the habitat environment before mosquito collection (Wiwatanaratanabutr and Kittayapong, 2009; Rosso et al, 2018; Thongsripong et al, 2018; Hu et al, 2020), and affect the DENV-2 loads of local mosquito population
Summary
Aedes (Stegomyia) albopictus (Skuse, 1894) is an anthropophilic mosquito that originated in Southeast Asia and has spread to many countries across all continents except Antarctica (Goubert et al, 2016) This species is a vector for more than 20 arboviruses, of which some are strongly pathogenic and transmissible, such as dengue virus (DENV), Chikungunya virus (CHIKV), and yellow fever virus (Gratz, 2004; Amraoui et al, 2019). The most devastating recent dengue fever epidemic occurred in 2014 in Guangzhou, Guangdong province, causing a total of 47,056 clinical cases and six deaths (Lai et al, 2015; Sun et al, 2017) In most of these past epidemics, Ae. albopictus was the sole DENV vector
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