Phylogeny and spatial distribution of Japanese encephalitis virus vector species in Cambodia.

In Southeast Asia, despite the use of Japanese encephalitis vaccines and vaccination coverage, Japanese encephalitis (JE) transmission is still a major public health issue. The main vectors of this virus are mosquitoes from the genus Culex, which diversity and density are important in Southeast Asia. The main vector species of Japanese encephalitis virus (JEV) in Cambodia belong to the Vishnui subgroup. However, their morphological identification solely based on the adult stage remains challenging, making their segregation and detection difficult. In order to identify and describe the distribution of the three main JEV vector species in Cambodia, namely Culex vishnui, Cx. pseudovishnui and Cx. tritaeniorhynchus, mosquito samplings were carried out throughout the country in different environments. Phylogenetic analysis of the cytochrome c oxidase subunit I (coI) gene using maximum-likelihood tree with ultrafast bootstrap and phylogeographic analysis were performed. The three main Culex species are phylogenetically separated, and represent two distinct clades, one with Cx. tritaeniorhynchus and the second with Cx. vishnui and Cx. pseudovishnui, the latter appearing as a subgroup of Cx. vishnui. The phylogeographic analysis shows a distribution of the Vishnui subgroup on the entire Cambodian territory with an overlapped distribution areas leading to a sympatric distribution of these species. The three JEV vector species are geographically well-defined with a strong presence of Cx. pseudovishnui in the forest. Combined with the presence of Cx. tritaeniorhynchus and Cx. vishnui in rural, peri-urban, and urban areas, the presence of JEV-competent vectors is widespread in Cambodia.

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.

Culex vishnui (Diptera: Culicidae): An Overlooked Vector of Arboviruses in South-East Asia.

Culex vishnui Theobald, 1901, a main vector of Japanese encephalitis virus (JEV), is widely distributed in the Oriental region where it often accounts for a great part of the culicid fauna. This species also has been found naturally infected with at least 13 other arboviruses of medical and veterinary importance. Females blood feed predominantly upon pigs and birds, but may readily bite cattle and humans. Because of its abundance, medical importance, and presence throughout ecological gradients among urban, peri-urban, and rural areas, Cx. vishnui potentially may serve as a bridge vector transmitting viruses from natural and wild hosts to humans. Being zoo- and anthropophagic, omnipresent in the Oriental region, and presenting strong resistance to many insecticide families, this overlooked mosquito species may pose a serious health risk in one of the most densely populated regions of the world.

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.

Variations in the carapace shape of whip spiders (Arachnida: Amblypygi).

Morphological studies often need to reference body size to correctly characterise the shape of organisms. In arthropods, the most commonly used reference for this is the length or width of the carapace, thorax, or the prosoma in the case of chelicerates. However, in the case of animals with unlimited growth, such as whip spiders, this measure could be irrelevant if growth is allometric. In this study, we analyse the ontogenetic modifications in prosoma outline shape in whip spiders during growth and compare the differences in shape between species. Differences are important for the relative prosoma width between species and, in the case of Damon medius, during growth in the juvenile stages, whereas the shape remains stable in mature stages. We conclude that a one-dimensional measure (i.e., length or width) suffices for mature specimens of a single species or family, but for larger studies, or when including immature specimens, at least the prosoma area (within the outline shape) should be used as a size estimator.

Monitoring insecticide resistance of adult and larval Aedes aegypti (Diptera: Culicidae) in Phnom Penh, Cambodia.

BACKGROUND: Dengue fever is a major public health concern in Cambodia, with thousands of cases every year in urban, suburban and rural areas of the country. The main vector of dengue fever in Cambodia is Aedes aegypti. The organophosphate larvicide temephos and adulticides belonging to the pyrethroid family have been widely used for decades by public health authorities to fight dengue vectors, but resistance of Ae. aegypti to these insecticides has been previously described for Cambodia. METHODS: In order to adapt the vector control strategy presently used in Cambodia, we tested 14 adulticides belonging to the carbamate, organochlorine, organophosphate, and pyrethroid insecticide families and three larvicides [temephos, spinosad and Bacillus thuringiensis ser. israelensis (Bti)] belonging to three different insecticide families (organophosphates, spinosyns and entomopathogenic bacteria). The standard procedures used here to test the adults and larvae of an Ae. aegypti population from Phnom Penh followed World Health Organization guidelines. RESULTS: For adults, high mortality rates were observed with carbamate, organophosphate and organochlorine (with the exception of dichlorodiphenyltrichloroethane) insecticides (i.e. between 87.6 and 100%), while low mortality rates were observed with all of the tested pyrethroid insecticides (i.e. between 1 and 35%). For larvae, no resistance against Bti was detected [resistance ratio (RR90 < 1.6)], but moderate resistance was observed for temephos and spinosad (RR90 < 5.6). CONCLUSIONS: The results of this study indicate that (i) Bti should be considered a serious alternative to temephos for the control of Ae. aegypti larvae; and (ii) the carbamate adulticides propoxur and bendiocarb should be employed instead of the widely used pyrethroid insecticides for the control of adult Ae. aegypti on land under mosaic farming and crop rotation in Cambodia, as the insects were found to be resistant to the latter types of insecticide. Research focusing on insecticide resistance and innovative and effective vector control strategies should be undertaken as a public health priority in Cambodia.

A review of Capezoum Adlbauer, 2003 (Coleoptera: Cerambycidae) with the description of two new species from the Succulent Karoo ecosystem in South-Africa.

Capezoum Adlbauer, 2003 is known only from male specimens. Herein, we describe two new species: Capezoum richardi sp. nov. and C. brunneopunctatus sp. nov., from the Northern Cape region in South-Africa. The discovery of these new species, one of them represented by both sexes, allowed us to describe the hitherto unknown female. Moreover, the genus is transferred to the tribe Xystrocerini and a key to the species of the genus is provided. Lastly, the position of Mythozoum Thomson, 1878 in Cerambycidae is discussed.

Checklist of the mosquito fauna (Diptera, Culicidae) of Cambodia.

Between 2016 and 2020, the Medical and Veterinary Entomology unit of the Institut Pasteur du Cambodge collected over 230,000 mosquitoes. Based on this sampling effort, a checklist of 290 mosquito species in Cambodia is presented. This is the first attempt to list the Culicidae fauna of the country. We report 49 species for the first time in Cambodia. The 290 species belong to 20 genera: Aedeomyia (1 sp.), Aedes (55 spp.), Anopheles (53 spp.), Armigeres (26 spp.), Coquillettidia (3 spp.), Culex (57 spp.), Culiseta (1 sp.), Ficalbia (1 sp.), Heizmannia (10 spp.), Hodgesia (3 spp.), Lutzia (3 spp.), Malaya (2 spp.), Mansonia (5 spp.), Mimomyia (7 spp.), Orthopodomyia (3 spp.), Topomyia (4 spp.), Toxorhynchites (4 spp.), Tripteroides (6 spp.), Uranotaenia (27 spp.), and Verrallina (19 spp.). The Cambodian Culicidae fauna is discussed in its Southeast Asian context. Forty-three species are reported to be of medical importance, and are involved in the transmission of pathogens.

TITLE: Liste des moustiques (Diptera, Culicidae) du Cambodge. ABSTRACT: Entre 2016 et 2020, plus de 230 000 moustiques ont été capturés par l'Unité d'Entomologie Médicale et Vétérinaire de l'Institut Pasteur du Cambodge. Sur la base de ces collectes, une liste des 290 espèces de moustiques présentes au Cambodge est présentée. Il s'agit de la première tentative de répertorier la faune Culicidae du pays. Quarante-neuf espèces sont signalées pour la première fois au Cambodge. Les 290 espèces appartiennent à vingt genres : Aedeomyia (1 sp.), Aedes (55 spp.), Anopheles (53 spp.), Armigeres (26 spp.), Coquillettidia (3 spp.), Culex (57 spp.), Culiseta (1 sp.), Ficalbia (1 sp.), Heizmannia (10 spp.), Hodgesia (3 spp.), Lutzia (3 spp.), Malaya (2 spp.), Mansonia (5 spp.), Mimomyia (7 spp.), Orthopodomyia (3 spp.), Topomyia (4 spp.), Toxorhynchites (4 spp.), Tripteroides (6 spp.), Uranotaenia (27 spp.) et Verrallina (19 spp.). La faune des Culicidés cambodgiens est discutée dans son contexte sud-est asiatique. Quarante-trois espèces sont d'importance médicale et impliquées dans la transmission de pathogènes.

Mosquito Vector Competence for Japanese Encephalitis Virus.

Japanese encephalitis virus (JEV) is a zoonotic pathogen mainly found in East and Southeast Asia and transmitted by mosquitoes. The objective of this review is to summarize the knowledge on the diversity of JEV mosquito vector species. Therefore, we systematically analyzed reports of JEV found in field-caught mosquitoes as well as experimental vector competence studies. Based on the investigated publications, we classified 14 species as confirmed vectors for JEV due to their documented experimental vector competence and evidence of JEV found in wild mosquitoes. Additionally, we identified 11 mosquito species, belonging to five genera, with an experimentally confirmed vector competence for JEV but lacking evidence on their JEV transmission capacity from field-caught mosquitoes. Our study highlights the diversity of confirmed and potential JEV vector species. We also emphasize the variety in the study design of vector competence investigations. To account for the diversity of the vector species and regional circumstances, JEV vector competence should be studied in the local context, using local mosquitoes with local virus strains under local climate conditions to achieve reliable data. In addition, harmonization of the design of vector competence experiments would lead to better comparable data, informing vector and disease control measures.

Host-Feeding Preference and Diel Activity of Mosquito Vectors of the Japanese Encephalitis Virus in Rural Cambodia.

Japanese Encephalitis (JE) is the most important cause of human encephalitis in Southeast Asia, and this zoonosis is mainly transmitted from pigs to human by mosquitoes. A better understanding of the host-feeding preference of Japanese encephalitis virus (JEV) major vectors is crucial for identifying risk areas, defining bridge vector species and targeting adapted vector control strategies. To assess host-feeding preference of JE vectors in a rural Cambodian area where JE is known to circulate, in 2017, we implemented four sessions of mosquito trapping (March, June, September, December), during five consecutive nights, collecting four times a night (6 p.m. to 6 a.m.), and using five baited traps simultaneously, i.e., cow, chicken, pig, human, and a blank one for control. In addition, blood meals of 157 engorged females trapped at the same location were opportunistically analyzed with polymerase chain reaction (PCR), using cow, pig, human, and dog blood primers. More than 95% of the 36,709 trapped mosquitoes were potential JE vectors. These vectors were trapped in large numbers throughout the year, including during the dry season, and from 6 p.m. to 6 a.m. Despite the apparent host-feeding preference of Culex vishnui, Cx. gelidus, and Cx. tritaenhyorhincus for cows, statistical analysis suggested that the primary target of these three mosquito species were pigs. Dog blood was detected in eight mosquitoes of the 157 tested, showing that mosquitoes also bite dogs, and suggesting that dogs may be used as proxy of the risk for human to get infected by JE virus.

Description of two new Obriini Mulsant, 1839 (Coleoptera: Cerambycidae) from the Tankwa Karoo biome in South Africa and Namibia.

Two new species of Capezoum: C. tankwakarooensis sp. nov. and C. museiconfluentiarum sp. nov. are described from the Succulent Karoo ecosystem in South Africa and Namibia.

Description of a new species of Capederces (Coleoptera: Cerambycidae: Cerambycinae) from South Africa.

A new species of longhorned beetle in the tribe Tillomorphini, Capederces madibai sp. nov., is described from the "Albany district" in south-eastern South Africa. Adult specimens are illustrated and compared with the only other known species from this previously mono-specific genus: C. hauseri Adlbauer, 2001. An illustration of the female of C. hauseri is provided for the first time.

The sterile insect technique for controlling populations of Aedes albopictus (Diptera: Culicidae) on Reunion Island: mating vigour of sterilized males.

Reunion Island suffers from high densities of the chikungunya and dengue vector Aedes albopictus. The sterile insect technique (SIT) offers a promising strategy for mosquito-borne diseases prevention and control. For such a strategy to be effective, sterile males need to be competitive enough to fulfil their intended function by reducing wild mosquito populations in natura. We studied the effect of irradiation on sexual maturation and mating success of males, and compared the sexual competitiveness of sterile versus wild males in the presence of wild females in semi-field conditions. For all untreated or sterile males, sexual maturation was completed within 13 to 20 h post-emergence and some males were able to inseminate females when 15 h old. In the absence of competition, untreated and sterile males were able to inseminate the same number of virgin females during 48 h, in small laboratory cages: an average of 93% of females was inseminated no matter the treatment, the age of males, and the sex ratio. Daily mating success of single sterile males followed the same pattern as for untreated ones, although they inseminated significantly fewer females after the ninth day. The competitiveness index of sterile males in semi-field conditions was only 0.14 when they were released at 1-day old, but improved to 0.53 when the release occurred after a 5-day period in laboratory conditions. In SIT simulation experiments, a 5:1 sterile to wild male ratio allowed a two-fold reduction of the wild population's fertility. This suggests that sterile males could be sufficiently competitive to mate with wild females within the framework of an SIT component as part of an AW-IPM programme for suppressing a wild population of Ae. albopictus in Reunion Island. It will be of interest to minimise the pre-release period in controlled conditions to ensure a good competitiveness without increasing mass rearing costs.