The dynamic of arbovirus vectors such as Aedes aegypti and Ae. albopictus remains poorly understood in large cities in central Africa. Here, we compared the larval ecology, geographical distribution and degree of infestation of Ae. aegypti and Ae. albopictus in Yaoundé, the capital city of Cameroon, and estimated their Stegomyia indices revealing a significant potential risk of arbovirus transmission. An entomological survey was conducted in April–May 2018 in a cluster of houses randomly selected. Each selected house was inspected, the number of inhabitants was recorded, and potential and positive containers for Aedes were characterized. Stegomyia and pupae-based indices were estimated. Overall, 447 houses and 954 containers were inspected comprising 10,801 immature stages of Aedes with 84.95% of Ae. albopictus and 15.05% of Ae. aegypti. Both species bred mainly in discarded tanks and used tyres, associated with turbid water and the presence of plant debris inside containers. Aedes albopictus was the most prevalent species in almost all neighbourhoods. The house index, Breteau index, and container index were higher for Ae. albopictus (38.26%, 71.81%, and 29.61%) compared to those of Ae. aegypti (25.73%, 40.93%, and 16.88%). These indices are high compared to the thresholds established by Pan American Health Organization and World Health Organization, which suggests a high potential risk of arbovirus transmission.

Aedes (Ae.) aegypti and Ae. albopictus are important vectors of arboviruses. Yet their blood-feeding pattern remains poorly characterised in Africa, including Cameroon. In this study, we characterised the blood-meal sources in both species collected from vegetation, household surroundings, and animal cages across four urban sites, one rural site, and a zoo-botanical garden where humans and animals in captivity are the main hosts. Overall, Aedes mosquitoes represented about half of 10,054 female mosquitoes collected, with Ae. albopictus strongly dominating Ae. aegypti among 5001 Aedes females, and only 5.95% of females visibly blood-fed. Sequencing a 748 base pairs (bp) fragment of the cytochrome oxidase I gene from 156 blood-fed abdomens yielded 126 high-confidence host assignments, of which 98.25% were humans, indicating a strong anthropophagic pattern in both species. Unpredictably, two Ae. albopictus individuals had fed on a baboon (Papio anubis) and a frugivorous bat (Pteropodidae), as confirmed by bio informatic analyses, highlighting the species’ opportunistic blood-feeding nature and providing preliminary molecular evidence consistent with a potential bridge-vector role in this setting. Despite the extreme anthropophagy of both species observed, results indicate that Ae. albopictus could also serve as a bridge vector enabling spillover of enzootic viruses to humans, including urbanised settings where wild animals are present. These findings emphasise the urgent need for enhanced arbovirus surveillance in Central Africa using a One Health approach.

Background: Reports of arboviral outbreaks are increasing, yet there are acknowledged shortfalls in surveillance data and outbreak preparedness on the African continent. The second part of this scoping review features Aedes vector–pathogen interactions, bionomics and species distribution. Methods: We reviewed studies published between 1980 and 2023 to synthesize existing information and identify knowledge gaps to guide future Aedes research and control in Africa. Results: 877 full-text articles were reviewed, 70 featured vector–pathogen interactions, 230 vector bionomics and 394 species distribution. Vector competence studies were limited to a handful of countries, highlighting knowledge gaps regarding urban, bridge and sylvatic vector species competence for major arboviruses. Aedes albopictus was highly competent for chikungunya virus with the E1-226V mutation, which has been implicated in epidemics where Ae. aegypti was displaced. Vector competence was dependent on virus lineage and mosquito population. Ae. aegypti competence to dengue virus was highly variable, whereas Ae. albopictus was an efficient vector of Zika virus for African but not Asian lineages. Discarded tires were the most frequently reported positive breeding habitats, ranking among the top three in 55% of publications, followed by other discarded items (cans, bottles, broken plastic items) and water storage containers; however, the relative importance varied by location. The pupal index was reported less frequently than traditional indices (container, Breteau and house indices), which co-occurred in 84% of studies reporting indices. As pupal counts are a better proxy for adult mosquito production, their wider use is recommended to identify locally important breeding sites for targeted control. Adult vector monitoring has shifted away from human landing catch towards BG-Sentinel and CDC-LT traps which may be less accurate proxies of human-vector contact, but efficiency can be improved using attractants. Ae. aegypti was highly anthropophilic and had a major biting peak before sunset. However, findings of Ae. aegypti biting at night-time and being zoophilic in some locations demonstrate the need for periodic monitoring, given changing environmental conditions. Conclusions: This review highlights how Aedes populations vary in their competence for key arboviruses, their breeding habitats, and biting behaviors across Africa. Understanding these patterns can guide targeted vector control and improve preparedness for arbovirus outbreaks.