Low Transmission of Chikungunya Virus by Aedes aegypti from Vientiane Capital, Lao PDR

In 2012-2013, chikungunya virus (CHIKV) was the cause of a major outbreak in the southern part of Lao People's Democratic Republic (Lao PDR). Since then, only a few imported cases, with isolates belonging to different lineages, were recorded between 2014 and 2020 in Vientiane capital and few autochthonous cases of ECSA-IOL lineage were detected in the south of the country in 2020. The CHIKV epidemiological profile contrasts with the continuous and intensive circulation of dengue virus in the country, especially in Vientiane capital. The study's aim was to investigate the ability of the local field-derived Aedes aegypti population from Vientiane capital to transmit the Asian and ECSA-IOL lineages of CHIKV. Our results revealed that, for both CHIKV lineages, infection rates were low and dissemination rates were high. The transmission rates and efficiencies evidenced a low vector competence for the CHIKV tested. Although this population of Ae. aegypti showed a relatively modest vector competence for these two CHIKV lineages, several other factors could influence arbovirus emergence such as the longevity and density of female mosquitoes. Due to the active circulation of CHIKV in Southeast Asia, investigations on these factors should be done to prevent the risk of CHIKV emergence and spread in Lao PDR and neighboring countries.

Automated summary

Between 2014 and 2020, only a few cases of the chikungunya virus (CHIKV) were imported to Lao PDR, with isolates from different lineages recorded in the capital city of Vientiane. In 2020, a few autochthonous cases of the ECSA-IOL lineage were detected in the southern part of the country. The study aimed to assess the ability of local Aedes aegypti mosquitoes from Vientiane to transmit the Asian and ECSA-IOL lineages of CHIKV. Results showed low infection rates but high dissemination rates, indicating a low vector competence for the tested CHIKV strains. Factors such as mosquito longevity and density may influence arbovirus emergence in the region.