Aedes aegypti vector competence studies: A review

Abstract

Aedes aegypti is the primary transmitter of the four viruses that have had the greatest impact on human health, the viruses causing yellow fever, dengue fever, chikungunya, and Zika fever. Because this mosquito is easy to rear in the laboratory and these viruses grow in laboratory tissue culture cells, many studies have been performed testing the relative competence of different populations of the mosquito to transmit many different strains of viruses. We review here this large literature including studies on the effect of the mosquito microbiota on competence. Because of the heterogeneity of both mosquito populations and virus strains used, as well as methods measuring potential to transmit, it is very difficult to perform detailed meta-analysis of the studies. However, a few conclusions can be drawn: (1) almost no population of Ae. aegypti is 100% naturally refractory to virus infection. Complete susceptibility to infection has been observed for Zika (ZIKV), dengue (DENV) and chikungunya (CHIKV), but not yellow fever viruses (YFV); (2) the dose of virus used is directly correlated to the rate of infection; (3) Brazilian populations of mosquito are particularly susceptible to DENV-2 infections; (4) the Asian lineage of ZIKV is less infective to Ae. aegypti populations from the American continent than is the African ZIKV lineage; (5) virus adaptation to different species of mosquitoes has been demonstrated with CHIKV; (6) co-infection with more than one virus sometimes causes displacement while in other cases has little effect; (7) the microbiota in the mosquito also has important effects on level of susceptibility to arboviral infection; (8) resistance to virus infection due to the microbiota may be direct (e.g., bacteria producing antiviral proteins) or indirect in activating the mosquito host innate immune system; (9) non-pathogenic insect specific viruses (ISVs) are also common in mosquitoes including genome insertions. These too have been shown to have an impact on the susceptibility of mosquitoes to pathogenic viruses. One clear conclusion is that it would be a great advance in this type of research to implement standardized procedures in order to obtain comparable and reproducible results.

Improved reference genome of the arboviral vectorAedes albopictus

“…The capacity of mosquitoes to acquire, disseminate and transmit viruses (i.e. vector competence) is a complex phenotype which is controlled by genetic elements of both the vector and the pathogen, as well as environmental variables (36). Understanding the complex relationship between vectors and pathogens requires understanding innate immunity in mosquitoes.…”

“…These are biological features important to estimate the epidemiological relevance of Ae. albopictus populations and to account for in the design of novel genetic-based strategies of vector control (36,52). As for the analyses of the landscape of viral integrations, we used whole-genome sequencing (WGS) data of mosquitoes from Tapachula and Tampon (53) to show the usefulness of AalbF2 in understanding the genomic diversity of Ae.…”

Genetic variation ofAedes aegyptipopulations from Ecuador

“…The haplotype 1 (H1) is the most abundant and may be related with the incidence of arboviral diseases in Ecuador. Souza-Neto et al (2019) mentions that Ae. aegypti shows complete susceptibility to get infected by Zika (ZIKV), dengue (DENV) and chikungunya (CHIKV), but not yellow fever viruses (YFV).…”

“…In Brazil Ae. aegypti is particularly susceptible to DENV-2 (Souza-Neto et al 2019). The apparent mixed presence of only two haplotypes in all geographic areas may have epidemiological, vector control and pest management implications.…”

Arbovirus Vectors of Epidemiological Concern in the Americas: A Scoping Review of Entomological Studies on Zika, Dengue and Chikungunya Virus Vectors

“…To determine vector competence, a species must be able to acquire, maintain, and transmit a pathogen, which is assessed through experimental infection studies. However, these studies are heterogeneous in both the mosquito populations and virus strains used, as well as methods measuring potential to transmit [210] The detection of viral particles in a wild-caught mosquitoes does not signify vector competence on its own, but it lends support to evidence from laboratory studies, when coupled with the observation of human host-feeding behaviour. Field studies are also important to assess the relative importance of competent vector species in disease maintenance and/or transmission.…”