Mosquito Species Composition and the Risk of Vector-Borne Disease at Live and Wet Markets in Laos

Live and wet markets (LWMs) form an important pillar of food supply in Asian countries, but the close interaction of animals and humans at markets creates an interface for disease transmission. The zoonotic risks associated with LWMs were highlighted after the onset of the COVID-19 pandemic. This study aimed to investigate the risk for mosquito-borne disease transmission at LWMs, through analyzing mosquito species composition and prevalence of flaviviruses, as well as general perception of the mosquito-borne diseases at LWMs in Lao PDR. Adult mosquito- and larval samples were collected from 15 LWMs. A total of 1129 adult mosquitoes were collected from five genera, of which Culex was the most common genus, with Cx. quinquefasciatus (qq.) being the most abundant species (85%). Moreover, 188 Culex larvae/pupae were collected, with a majority ovipositioned in water accumulated by the activities of LWMs, such as frequent water and ice distribution to keep the food fresh. All collected mosquitoes were grouped into 184 pools and were analyzed by a Pan-Flavi RT-PCR assay, with sequencing of suspected positives. No pathogenic flaviviruses were found from collected mosquitoes; however, mosquito-specific orthomyxoviruses were identified. The study questionnaire indicated a high awareness regarding mosquitoes as a source of disease transmission. Conclusively, accumulated water from LWMs is a focal point for mosquito oviposition and propagation, especially in larger-sized markets, enabling the zoonotic transmission of mosquito-borne diseases. This suggests implementing mosquito-mitigation measures such as wastewater management to prevent diseases associated with mosquitoes. Author SummaryMosquito-borne diseases, especially flaviviruses, have had a rapid increase in Asian regions in the past decade. Live and wet markets (LWMs) are common sources for food in Asia and have repeatedly been associated with the risk of zoonotic transmission, especially after the COVID-19 pandemic. We aimed to identify the mosquito species and explore associated viruses circulating the markets in Lao PDR, to evaluate the risks of mosquito-borne diseases. Among collected mosquitoes, Culex was recorded as the most prevalent genera. The most common mosquito oviposition site was stagnated water in the market, especially in larger LWMs. One larval pool was found positive to two mosquito-specific orthomyxoviruses, but no pathogenic flaviviruses were detected. This study demonstrates that live and wet markets a common site for mosquito circulation and oviposition, highlighting the risk of mosquito-borne disease transmission at such markets.