Mangroves are a dominant ecosystem interface between land and sea [1], forming distinctive shallow-water marine communities in tropical and subtropical waters. They provide various ecosystemic functions, such as coastal protection against cyclones and tsunamis, protection of the shoreline, and carbon sequestration [2]. Due to the lengthy coastline and wide range of climate conditions, mangrove forests cover large areas of Asian coastlines [2]. Cambodia hosts the tenth largest mangrove ecosystem in Asia [3]. Its mangrove areas are distributed within 4 provinces: 79.8% in Koh Kong province (41,122 ha), 14.6% in Sihanouk province (7539 ha), 4.7% in Kampot province (2444 ha), and 0.9% in Kep province (498 ha) [3, 4]. Between 1989 and 2017, about 42% (36,810 ha) of the mangrove forests in Cambodia were cleared [3]. Despite a recently slowing pace [3], clearing continues, and costal anthropization in the region is booming.
Typically, mangrove forests, despite having a low plant diversity, are insect-species rich, having a very adapted fauna [5]. Notably, these areas, through the diversity of the aquatic habitat they provide, are well-known for their concentration of mosquitoes [6, 7, 8, 9]. These hematophagous insects have been found to form a great part of the mangrove entomological community, and in Southeast Asia are found to be particularly diversified in Malaysia, Thailand, Sumatra, and the Philippines [10].
Urbanization of mangrove forests increases potential interactions between humans, wild mosquitoes, and potentially new infectious diseases [11, 12]. Continuous ecological change, including fragmentation of natural ecosystems, may increase the probability of human–vector contact, and, consequently, the possibility of outbreaks of emerging and re-emerging arboviruses [13]. Previous studies on the virome of saltmarsh mosquito demonstrated the presence of several human-pathogenic viruses from the flavivirus and alphavirus families [11, 14] and their risk of emergence. Given the increasing focus on mangrove conservation across Southeast Asia [15], understanding the mosquito diversity, and subsequently analyzing their virome, is critical in being able to estimate the risks of the emergence and outbreaks of mosquito-borne diseases [14]. However, to our knowledge, there are no previous studies on the composition of the Culicidae fauna in the Cambodian mangroves. To our knowledge, the present article reports for the first time the mosquito fauna of the mangrove forests in Koh Kong province, providing a baseline of their biodiversity in southwestern Cambodia.
This research was approved by Cambodian government authority and allowed by the Ministry of Environment (permit No. 1443, issued on November 15, 2018), and by the Directorate General of Nature Conservation and Protection (permit No. 057, issued on February 14, 2019).
For the field survey, 3 main sites were investigated. The first one was on Koh Sralau island, located 1.43 km SSW of Sralau village (11°4502N, 103°0645E, World Geodetic System (WGS) 84, geographical coordinates in decimal degrees). There, 6 U.S. Centers for Disease Control and Prevention (CDC) Mini Light Traps and 6 BG-Sentinel 1 traps (Biogents) were placed in the mangrove forest for 3 consecutive days (
Location of the 3 different sampling sites on Koh Kong. The inset in white represents Cambodia, showing the general location of Kho Kong (red square). Site 1: Koh Sralau island, 1.43 km SSW of Sralau village (11°4502N, 103°0645E, WGS84). Site 2: Koh Kapi, 1 km E of the city (11°4544N, 103°0207E, WGS84). Site 3: Koh Moul island, 2.5 km S and 7.2 km SW of Koh Kapi and Koh Sralau, respectively (11°4329N, 103°0063E, WGS84), and a beach nearby (11°4306N, 103°0129E, WGS84). Modified from Google Maps version 10.66.1 (imagery date November 1, 2019); imagery and data attributions: imagery CNES/Airbus, Landsat/Copernicus, Maxar Technologies, ©2022 TerraMetrics; map data SIO, NOAA, U.S. Navy, NGA, GEBCO ©2022 Google.
Adult mosquitoes were collected using BG-Sentinel 1 Mosquito Traps, 7.5–12 V, coupled with BG-Lure (BioQuip) and CDC Mini Light Traps (BioQuip), baited with incandescent light, with dry ice (solid CO2, which sublimes to release CO2 gas) placed in a dispenser next to the traps. Mosquitoes were killed humanely using carbon dioxide. Each trapping location was visited daily to remove the collected insects.
The fieldwork was carried from at the end of March 2019, for the dry season, and in mid-November 2019 for the rainy season. The meteorological conditions observed in 2019 did not differ from those of the previous years. Climate data were obtained from climateengine.org (
Meteorological conditions in Koh Kong province in 2019. Climate data were obtained from climateengine.org. Temperatures (solid line) were gathered from Terraclimate and CFSR satellite data, and precipitation (gray bars) from CHIRPS satellite data.
The mosquitoes were kept individually in Eppendorf tubes, identified on the field, and kept in an electric tank cooler at 4°C for the time of the mission. They were identified using their diagnostic morphological characters [16, 17, 18, 19, 20, 21, 22, 23, 24, 25]. The identification was confirmed by the examination of the original description of the species. Voucher specimens are deposited in the collection of the Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
In total 3107 mosquitoes were collected, of which 89.4% (2777 specimens) were identifiable to the species level (
List and total number of mosquitoes species collected in Koh Kong province
Aedes (5 species) | 141 | ||||||
9 | 1 | 10 | |||||
1 | 6 | 1 | 3 | 1 | 2 | 14 | |
4 | 4 | ||||||
30 | 30 | ||||||
1 | 1 | ||||||
8 | 41 | 1 | 31 | 1 | 82 | ||
2 | 4 | 1 | 7 | ||||
1 | 1 | ||||||
13 | 20 | 1 | 34 | ||||
5 | |||||||
1 | 1 | 1 | 3 | ||||
1 | 1 | 2 | |||||
66 | |||||||
1 | 1 | 9 | 11 | ||||
51 | 51 | ||||||
2 | 2 | 4 | |||||
2571 | |||||||
21 | 1 | 22 | |||||
6 | 1 | 7 | |||||
1 | 1 | ||||||
1 | 1 | ||||||
6 | 6 | ||||||
682 | 1103 | 89 | 1874 | ||||
3 | 3 | ||||||
27 | 120 | 230 | 85 | 8 | 2 | 472 | |
37 | 7 | 44 | |||||
8 | 109 | 1 | 3 | 4 | 125 | ||
1 | |||||||
1 | 1 | ||||||
120 | |||||||
81 | 1 | 82 | |||||
2 | 11 | 13 | |||||
6 | 6 | ||||||
2 | 2 | ||||||
Mansonia sp. | 2 | 15 | 17 | ||||
8 | |||||||
1 | 1 | ||||||
1 | 3 | 4 | |||||
3 | 3 | ||||||
110 | |||||||
6 | 6 | ||||||
1 | 1 | ||||||
9 | 53 | 9 | 71 | ||||
1 | 20 | 1 | 2 | 4 | 4 | 32 | |
43 | |||||||
5 | 5 | ||||||
14 | 6 | 20 | |||||
Unknown | 13 | 2 | 3 | 18 | |||
Grand total | 89 | 1314 | 237 | 1333 | 19 | 115 | 3107 |
Number of species | 12 | 28 | 2 | 13 | 4 | 6 | 34 |
Number of species per collection site | 32 | 13 | 7 | ||||
Shannon index | 1.7 | 1.5 | 0.09 | 0.06 | 0.9 | 0.7 | |
Shannon index | 1.6 | 0.9 | 0.9 | ||||
Simpson index | 0.7 | 0.6 | 0.03 | 0.3 | 0.4 | 0.3 | |
Simpson index | 0.6 | 0.4 | 0.4 |
The genus
The core of the reserve, Koh Sralau, located in the mangrove forest, harbored the highest Culicidae diversity with 32 species (
Only 8 species could be found through the year:
During our collection, a total of 12 species from 5 different genera are reported to be of medical importance (
List of medically important mosquito species in Koh Kong
DENV, ZIKV, CHYKV, WNV, YFV | [26, 27, 28] | |
DENV, ZIKV, CHYKV, JEV, WNV | [26, 27, 28] | |
MAL | [26, 29] | |
JEV, FILWB | [26, 27, 30] | |
JEV, FILBM, FILWB | [26, 30] | |
JEV | [26, 30] | |
JEV | [26, 27, 30] | |
ZIKV, JEV, WNV | [26, 27, 30] | |
FILBM, JEV | [26, 30, 31, 32] | |
JEV | [26, 27, 30] | |
JEV | [26, 27, 30] | |
WNV | [26] |
CHIKV, chikungunya virus; DENV, dengue virus; FILBM, filariosis by
The present study provides—to our knowledge—the first list of mosquitoes in the mangrove forests of Koh Kong. Besides providing a baseline for future researches in this conserved area, it is another step forward in assessing the local risks of mosquito-borne disease.
Of the 290 known species recorded from Cambodia [26], the mosquitoes sampled in Koh Kong, with 37 recorded species, represent 12.7% of the Cambodian fauna. The Culicidae fauna of Koh Kong is quite diverse compared with that in the mangrove forest at the mouth of the Bangpakong river in Thailand, where only 14 species were recorded [33]. The most extensive work in the southern Asian region has been conducted in the Indian mangrove forests, where 43 species were recorded in Bhitarkanika (Orissa; [6]), 19 in the Sunderbans (West Bengal; [7]), 53 in the Andaman Islands [8], and 12 species in Coringa (Andhra Pradesh; [9]). Typically, mangrove forests, despite having a low plant diversity, are insect-species rich, having a very adapted fauna [5].
Most of the species collected belonged to the genus
In total, 5 species of
The genus
The genera
In total, 12 species of medical importance belonging to 5 different genera were collected, and represented 77.9% (n = 2423) of all collected mosquitoes. Most were collected during the rainy season.
Some 9 different species are vectors of Japanese encephalitis virus (JEV). The 2 main JEV vector species recognized are
The 2
Although only one specimen of parasite-carrying mosquitoes was captured,
On a more general note, of the 12 medically important species, 3 of them were caught in each of the 3 sites.
Limitations of the present study include that each site was visited only once per season (rainy and dry) and that only BG and light-traps were used to collect mosquitoes. Increasing the diversity of traps and methods such as larvae collection are the best ways to improve the diversity of the collected Culicidae.
While the clearing of the Cambodian mangroves pace is slowing due to reforestation practices and proper law enforcement, further efforts are needed in this direction [3]. This coastal habitat could provide a buffering effect toward vector borne disease [11], and negatively affects arbovirus transmission [11]. While the conservation of biodiversity-rich areas is essential, with the striking resurgence of arboviruses, such as Zika, dengue, yellow fever, or chikungunya this century [55], the knowledge of blood-sucking arthropods—potentially vectors of diseases—and the pathogens they can carry is becoming increasingly necessary for public health considerations. In the present study, 2 species of medical importance were found throughout the year, and across all the different sites, namely