Mosquito diversity (Diptera: Culicidae) and medical importance in four Cambodian forests.

BACKGROUND: A total of 290 mosquito species are recorded in Cambodia among which 43 are known vectors of pathogens. As Cambodia is heavily affected by deforestation, a potential change in the dynamic of vector-borne diseases (VDBs) could occur through alteration of the diversity and density of sylvatic vector mosquitoes and induce an increase in their interactions with humans. Understanding mosquito diversity is therefore critical, providing valuable data for risk assessments concerning the (re)emergence of local VBDs. Consequently, this study mainly aimed to understand the spatial and temporal distribution of sylvatic mosquito populations of Cambodia by determining which factors impact on their relative abundance and presence. METHODS: A study was conducted in 12 sites from four forests in Cambodia. All mosquitoes, collected during the dry and rainy seasons, were morphologically identified. The diversity and relative density of mosquito species in each site were calculated along with the influence of meteorological and geographical factors using a quasi-Poisson generalized linear model. RESULTS: A total of 9392 mosquitoes were collected belonging to 13 genera and 85 species. The most represented genera were Culex, accounting for 46% of collected mosquitoes, and Aedes (42%). Besides being the most abundant species, Culex pseudovishnui and Aedes albopictus, which are known vectors of numerous arboviruses, were present in all sites during both dry and rainy seasons. The presence of mosquito species reported to be zoo-anthropophilic feeders was also observed in both forested and urban areas. Finally, this study demonstrated that altitude, temperature and precipitation impacted the abundance of mosquitoes but also influenced species community composition. CONCLUSION: The results indicate an important diversity of mosquitoes in the four forests and an influence of meteorological and geographical factors on their community. Additionally, this work highlights in parallel the abundance of species considered to be of medical importance and therefore underlines the high risk of pathogen emergence/re-emergence in the region.

Mosquito (Diptera: Culicidae) diversity and medical importance in Koh Kong mangrove forests, Cambodia.

Background: Mangroves are an ecosystem interface between land and sea, forming distinctive shallow-water marine communities in tropical and subtropical waters. The mangrove forest surface in Cambodia is being reduced due to deforestation. Because the mangrove type of ecosystem generally hosts a great diversity of mosquitoes, the urbanization of these ecosystems will increase interactions between humans and wild mosquitoes, and might thus serve as a potential source of new infectious diseases. Understanding mosquito diversity and analyzing their virome is critical to estimate the risk of emergence or future outbreaks of mosquito-borne diseases. Objective: To understand the mosquito diversity of mangrove forests of Koh Kong province (Cambodia). Methods: In 2019, the mosquito fauna was sampled for 3 consecutive days using BG-Sentinel and light traps, in 3 locations in the mangrove forests of Koh Kong province (Cambodia) during both dry and rainy seasons. Results: A total of 3107 samples were collected, belonging to 10 genera for 34 species. The Culex genus was the most diverse, accounting for 10 species. One species, Culex sitiens, represented over 60% of all collected mosquitoes. A total of 12 medically important species were recorded, 2 species, Aedes (Stegomyia) albopictus and Culex vishnui, were collected in all sites and during both the dry and rainy seasons, highlighting a potential risk of these species acting as bridge vectors. Conclusions: If new arboviruses were to be recorded in this peculiar area, it would indicate that the mosquito species found have the potential to act as a bridge between sylvatic and anthropogenic arboviruses.

DISEASE SCREENING IN SOUTHERN RIVER TERRAPINS ( BATAGUR AFFINIS EDWARDMOLLI) IN CAMBODIA.

Southern River terrapins ( Batagur affinis) are among the most critically endangered turtles in the world. To augment the Cambodia population, a head-start program was established for the endemic subspecies Batagur affinis edwardmolli in 2006, and in 2015, prerelease health assessments were performed on 70 subadults (hatch years, 2006-2011). Combined choanal/cloacal swab samples ( n = 70) were collected and screened by polymerase chain reaction (PCR) for Mycoplasma, herpesvirus, and ranavirus. Cloacal samples ( n = 50) were also collected and cultured for Salmonella sp. Of 70 tested samples, six (8.6%) were positive for Mycoplasma, and all other PCR and culture test results were negative. Phylogenetic analysis of the 16S ribosomal RNA gene placed the Mycoplasma sp. from B. affinis edwardmolli in the chelonian Mycoplasma cluster that groups within the Mycoplasma pulmonis clade. This mollicute was not associated with clinical disease (defined as observable clinical abnormalities, such as depression, lethargy, respiratory signs, and anorexia) and is likely part of the endemic microbial flora of these terrapins.