Aedes Mosquito Distribution along a Transect from Rural to Urban Settings in Yaoundé, Cameroon

Introduction: The surveillance of mosquito vectors is important for the control of arboviruses diseases worldwide. Detailed information on the bionomics and distribution of their main vectors, Aedes aegypti and Aedes albopictus, is essential for assessing disease transmission risk and for better planning of control interventions. Methods: Entomological surveys were carried out from November 2019 to November 2020 in six localities of Yaoundé city following a transect from urban to rural settings: two urban (Obili, Mvan), two peri-urban (Simbock, Ahala) and two rural areas (Lendom, Elig-essomballa)—during rainy and dry seasons. All water containers were inspected. Aedes mosquito abundance, species distribution and seasonal distribution patterns were compared using generalized linear models. Stegomyia indexes were estimated to determine the risk of arbovirus transmission. Results: A total of 6332 mosquitoes larvae were collected (2342 in urban areas, 1694 in peri-urban areas and 2296 in rural sites). Aedes species recorded included Ae. albopictus, Ae. aegytpi, Ae. simpsoni and Aedes spp. High mosquito abundance was registered in the rainy season (4706) compared to the dry season (1626) (p < 0.0001). Ae. albopictus was the most abundant Aedes species in urban (96.89%) and peri-urban (95.09%) sites whereas Ae. aegypti was more prevalent in rural sites (68.56%) (p < 0.0001). Both species were found together in 71 larval habitats. Ae. albopictus was mostly found in discarded tires (42.51%), whereas Ae. aegypti was more prevalent in plastic containers used for storing water (65.87%). The majority of Aedes mosquitoes’ breeding places were situated close to human dwellings (0–10 m). Conclusion: Uncontrolled urbanization seems to greatly favour the presence of Aedes mosquito species around human dwellings in Yaoundé. Controlling Aedes mosquito distribution is becoming urgent to reduce the risk of arbovirus outbreaks in the city of Yaound

Investigation on transvorial transmission of chikungunya and dengue viruses in the wild population of Aedes mosquitoes at selected rural localities in Kuching Sarawak, Malaysia

Chikungunya virus (CHIKV) and dengue virus (DENV) are mosquito-borne viruses transmitted by Aedes aegypti and Aedes albopictus. CHIKV has become endemic in Malaysia since its reemergence in 2006, whereas DENV was first reported in Malaysia in 1902. In 2009, Kampung Pulau Salak in Kuching, Sarawak, Malaysia was one of the areas affected by chikungunya outbreak. Hence, this study was conducted to investigate the potential vector and determine the presence of CHIKV and DENV transovarial transmission among the mosquito population in Kampung Pulau Salak and Kampung Tanjong Bako, Kuching, Sarawak. Mosquito larvae were collected from ovitraps and discarded receptacles found in both villages. The emerged Aedes mosquitoes were pooled (223 pools) according to sex, species, and study site before being subjected to RNA extraction and two-step reverse-transcription polymerase chain reaction (RT-PCR). The species of Aedes mosquito caught in both villages were Ae. albopictus and Ae. aegypti which comprises 95.8% and 4.2% of the total number of Aedes mosquito collected respectively. CHIKV was detected in one male and one female pool of the emerged adults of Ae. albopictus collected from Kampung Pulau Salak, which belongs to the East/Central/South/African (ECSA) genotype, whereas DENV serotype 2 (DENV-2) was detected in one pool of male and two pools of female of emerged Ae. albopictus collected from the same village. CHIKV and DENV were not detected in the emerged Aedes mosquitoes collected from Kampung Tanjong Bako. The presence of CHIKV and DENV in the emerged adults of mosquitoes revealed evidence of transovarial transmission among the population of Ae. albopictus in Kampung Pulau Salak, and because Ae. albopictus is the major species collected from the site, this study indicates that the species may be the primary vector of the viruses in the village