Anopheles ecology, genetics and malaria transmission in northern Cambodia

Abstract

In the Greater Mekong Subregion, malaria cases have significantly decreased but little is known about the vectors or mechanisms responsible for residual malaria transmission. We analysed a total of 3920 Anopheles mosquitoes collected during the rainy and dry seasons from four ecological settings in Cambodia (villages, forested areas near villages, rubber tree plantations and forest sites). Using odor-baited traps, 81% of the total samples across all sites were collected in cow baited traps, although 67% of the samples attracted by human baited traps were collected in forest sites. Overall, 20% of collected Anopheles were active during the day, with increased day biting during the dry season. 3131 samples were identified morphologically as 14 different species, and a subset was also identified by DNA amplicon sequencing allowing determination of 29 Anopheles species. The investigation of well characterized insecticide mutations (ace-1, kdr, and rdl genes) indicated that individuals carried mutations associated with response to all the different classes of insecticides. There also appeared to be a non-random association between mosquito species and insecticide resistance with Anopheles peditaeniatus exhibiting nearly fixed mutations. Molecular screening for Plasmodium sp. presence indicated that 3.6% of collected Anopheles were positive, most for P. vivax followed by P. falciparum. These results highlight some of the key mechanisms driving residual human malaria transmission in Cambodia, and illustrate the importance of diverse collection methods, sites and seasons to avoid bias and better characterize Anopheles mosquito ecology in Southeast Asia.

Mosquitoes (Diptera: Culicidae) from Villages and Forest Areas of Rural Communes in Khanh Hoa and Binh Phuoc Provinces, Vietnam

“…Many Anopheles samples were collected during the first hour of collection (between 6 pm and 7 pm), indicating that peak host-seeking behavior may occur earlier than 6 pm, possibly during the day time, especially in dark environments, such as in forest areas in Khanh Hoa and Binh Phuoc. This may not be an isolated observation as biting activity during the day was observed in Anopheles species in northern Cambodia ( Vantaux et al 2021 ), and in Laos ( Marcombe et al 2020 ). Herein, only CBT was conducted, thus, we were not able to infer the anthrophophily of Anopheles species in the malaria transmission context.…”

An inventory of human night-biting mosquitoes and their bionomics in Sumba, Indonesia

“…This study revealed a wide diversity of night-time human host seeking mosquito species in Sumba that potentially transmit multiple vector borne diseases. The presence of night biting vectors of non-malaria diseases warrants the careful application of the HLC technique to ensure the safety of volunteers conducting the mosquito trappings [ 53 , 54 ], or the implementation of other innovative tools for adult mosquito collection, such as the double net trap [ 55 ] and Host Decoy Trap [ 44 ].…”

Investigating the epidemiological factors responsible for malaria transmission dynamics

“…Malaria remains a serious public health challenge in Tropical Countries of the World especially in Sub-Saharan Africa [1,2]. The malaria disease is being transmitted by a Plasmodium-infected female Anopheles mosquito, when it comes in contact with the uninfected human host [3,4]. However, the uninfected Anopheles mosquito can also be infected with Plasmodium sppwhen it comes in contact with a Plasmodium-infected human host and it can retransmit the malaria disease.to another uninfected human host [5].…”