Evaluating the Role of Anopheles Mosquitoes in the Global Spread of Arboviruses: A Review of Laboratory-Confirmed Viral Competence

Mosquito-borne diseases are a major global health concern, infecting up to 700 million people annually and causing over one million deaths. Of the several genera of biting mosquito, species of Anopheles are mostly studied for their ability (termed vector competence) to transmit Plasmodium protozoan parasites, some species of which cause malaria. More than 480 species of Anopheles have been described worldwide and about 70 of these are responsible for Plasmodium spp . transmission. However, the focus on Anopheles as vectors of Plasmodium has led to a relative lack of study about the ability of Anopheles to transmit viruses.

Some Anopheles species have been previously confirmed competent for various arboviruses. In most cases they are secondary vectors, with relatively low competence, contributing to overall transmission while other species of mosquito or other vector are responsible for sustained transmission. While secondary vectors may contribute little to transmission, they may play important epidemiological roles by extending the length of the season and/or providing a means of overwintering.

Here, we conducted an extensive review of scientific repositories, accessing a diverse range of journals and reports to build an exhaustive database of known Anopheles competence for arboviruses. Opinion pieces, modelling papers lacking experimental confirmation, and papers without vector competence data were excluded. In total, we reviewed 7,343 papers, and after exclusions, we retained 427 papers.

We analysed these data, cross referenced with ability to diapause and geographical range. Our results show that some Anopheles spp. have the potential to be secondary vectors of some arboviruses, as well as undergoing diapause as adults in temperate regions of their range. Hence, we infer they could also play an epidemiologically important role in the overwintering of mosquito-borne viruses.

Author Summary

Mosquito borne diseases remain a global health challenge, causing over a million deaths annually. Though Anopheles mosquitoes are widely studied for their spread of parasites that cause malaria, much less is known about their interaction with viruses. In this study we reviewed scientific articles to identify their role in the spread of mosquito-borne viruses. We examined studies that showed experimental evidence of transmission in the laboratory, and thus could potentially contribute to transmission as secondary vectors. Additionally, some Anopheles species in temperate regions can survive winter in a dormant state (diapause) as adults, which could enable viruses to persist between transmission seasons. Together, these results suggest that Anopheles mosquitoes may play a larger role in virus transmission than is currently appreciated, especially in temperate regions.