# Vector competence of Aedes albopictus and Aedes aegypti from the islands of the Southwestern Indian Ocean for epidemic Zika, dengue, and chikungunya viruses

## TL;DR

This study assesses the ability of mosquitoes from the Southwestern Indian Ocean to transmit Zika, dengue, and chikungunya viruses, finding that they can spread dengue and chikungunya but not Zika.

## Contribution

The study evaluates vector competence of local mosquito populations for three arboviruses, revealing species-specific and virus-specific transmission efficiencies.

## Key findings

- Mosquito lines were not competent for Zika virus transmission.
- Transmission efficiencies reached 35.4% for dengue virus and 62.5% for chikungunya virus.
- Days post-exposure significantly influenced vector competence parameters.

## Abstract

Aedes albopictus and Aedes aegypti are key vectors involved in the transmission of human pathogens worldwide. Epidemiological studies have demonstrated varying levels of arbovirus transmission by these mosquito vectors, leading to an increasing number of investigations that assess vector competence (the ability of an insect to become infected and subsequently transmit a pathogen) of Ae. albopictus and Ae. aegypti lines, to decipher the risks associated with each species. In this study, we evaluated the vector competence of Ae. albopictus and Ae. aegypti lines from the Southwestern Indian Ocean (SWIO) for three arboviruses: Zika virus (ZIKV), dengue virus serotype-1 (DENV-1), and chikungunya virus (CHIKV).

Ten mosquito lines (eight Ae. albopictus and two Ae. aegypti lines), collected from five islands within SWIO (the Seychelles, the Comoros, and the Mascarene archipelagoes), were exposed to epidemic strains of ZIKV, DENV-1, and CHIKV. Three vector competence parameters (infection rate [IR], dissemination efficiency [DE], and transmission efficiency [TE]) were assessed at different days post exposure (dpe) to infectious blood meals, using plaque forming unit (PFU) assays. In addition, viral loads were quantified in positive saliva. These parameters were then compared between mosquito lines, geographic origins, and dpe for each virus.

None of the mosquito lines were competent for the ZIKV strain tested. In contrast, both Ae. albopictus and Ae. aegypti lines were competent vectors for the strains of DENV-1 and CHIKV tested, with transmission efficiencies reaching 35.4% for DENV-1 and 62.5% for CHIKV. For both mosquito species, statistical analyses revealed that dpe significantly influenced vector competence parameters, whereas the geographic origin of mosquito lines did not.

The observed vector competence patterns for the three tested viruses might partly explain their current epidemiology in the SWIO. This approach should involve a larger number of Ae. aegypti lines and should be extended to other ZIKV, DENV, and CHIKV strains, as well as to viruses not currently reported in the region, to better assess the risk of (re-)emergence of mosquito-borne viruses in the SWIO.

The online version contains supplementary material available at 10.1186/s13071-025-07193-0.