Patterns of Ecological Adaptation of Aedes aegypti and Aedes albopictus and Stegomyia Indices Highlight the Potential Risk of Arbovirus Transmission in Yaoundé, the Capital City of Cameroon.

Armel N Tedjou,Theodel A Wilson-Bahun,Flobert Njiokou,Charles S Wondji,Aurélie P Yougang,Basile Kamgang

doi:10.3390/pathogens9060491

Abstract

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.

Highlights

Aedes-borne diseases such as dengue, yellow fever, Zika and chikungunya have emerged in several tropical and subtropical regions worldwide [1]
The proportion of containers infested by Ae. albopictus was significantly higher than that infested by Ae. aegypti (χ2 = 37.78, df = 1, p < 10−9 )
The proportion of containers infested by Ae. albopictus (28.1%) was significantly higher than that infested by Ae. aegypti (15%) in downtown as well as in suburban (Ae. albopictus: 44.7%; Ae. aegypti: 18.6%) areas (p < 0.01), whereas no significant difference was observed in rural areas (p > 0.05) (Table S1)

Summary

Introduction

Aedes-borne diseases such as dengue, yellow fever, Zika and chikungunya have emerged in several tropical and subtropical regions worldwide [1]. The viruses that cause these diseases are transmitted to humans by a bite from infected mosquitoes belonging to the Aedes genus, notably Aedes aegypti (Linnaeus 1762) and Aedes albopictus (Skuse 1894) [2]. Native to the African continent [3,4], has a cosmo-tropical distribution while. Ae. albopictus, originating from the south-east Asian forest, has invaded all five continents over the Pathogens 2020, 9, 491; doi:10.3390/pathogens9060491 www.mdpi.com/journal/pathogens. Despite the fact that both species have a different origin, these mosquitoes have a similar ecology, ovipositing in man-made water containers [13,14] and feeding generally on human blood [15,16]

Methods

Results

Conclusion