Expansion ofAedes africanus(Diptera: Culicidae), a sylvatic vector of arboviruses, into an urban environment of Abidjan, Côte d'Ivoire

Abstract

In 2008, an outbreak of yellow fever occurred in Abidjan. The entomological investigations confirm that Abidjan is at risk of yellow fever with a suspicion of the National Park of Banco (NPB) forest as a likely area of re‐emergence. This study aims to assess the dispersion of sylvatic vectors of arboviruses from the NPB forest to the surrounding areas (Andokoi and Sagbé). The sampling was done in the rainy season using the WHO layer‐traps technique. Among the six species of Aedes sampled, Aedes aegypti and Aedes africanus were the potential vectors of arboviruses. Both species were collected in Sagbé but only Ae. aegypti in Andokoi. Only Ae. aegypti were present 400 and 800 m from NPB forest, but at 200 m, it showed respective proportions of 75.5% and 87.5% in Sagbé and Andokoi. In the NPB forest, however, Ae. africanus has been the predominant species. The study showed the presence of Ae. aegypti in Andokoi and Sagbé. However, Ae. africanus was found in the NPB forest and in the 200 m radius in Sagbé. The establishment of an entomological surveillance program in all areas would therefore be essential for the prevention of arboviruses outbreaks in Abidjan.

Diverse novel Wolbachia bacteria strains and genera-specific co-infections with Asaia bacteria in Culicine mosquitoes from ecologically diverse regions of Cameroon

“…As Aedes collections in the West Region were heavily dominated by Ae. africanus - a vector of YFV in forest and rainforest regions in Sub-Saharan Africa 50 , we compared Wolbachia and Asaia prevalence rates for pooled mono-specific RNA pools (n=97) to look for any potential co-infections within this species. Wolbachia was detected in 100.00% of pools (97/97) and a high Asaia prevalence rate of 96.91% (94/97) pools was also seen, demonstrating a high likelihood of co-infections occurring in this species.…”

Seasonal variation and intra urban heterogeneity of the entomological risk of transmission of dengue and yellow fever in Abidjan, Côte d'Ivoire

“…The absence of this species from the mosquitoes fauna collected during our surveys could be due to the fact that A. albopictus has not yet adapted to local breeding sites. This species preferentially breeds in containers containing plant debris or surrounded by vegetation (Kamgang et al, 2010), but beyond that, this species has not been found in Abidjan in several other studies (Guindo‐Coulibaly et al, 2019; Kpan et al, 2021; Zahouli et al, 2016). This may be explained by the absence of A. albopictus beyond its site of introduction at the coastal port.…”

“…The main vector of this infection during these epidemics was the A. aegypti mosquito. A. aegypti has been reported in high proportions during recent entomological investigations carried out in Abidjan city (Guindo-Coulibaly et al, 2019;Zahouli et al, 2017). The mosquitoes are in permanent contact with humans who constantly create favourable conditions for their development (Koné et al, 2013).…”

“…These arboviruses are transmitted by Aedes mosquitoes, among which Aedes aegypti represents one of the main vectors (Bruce, 2005; Christopher et al, 2017; Gubler, 2002). This species has been repeatedly listed during entomological investigations in the district of Abidjan (Guindo‐Coulibaly et al, 2010, 2019; Konan et al, 2009; Zahouli et al, 2016). Although it mainly colonizes domestic water storage containers (Konan et al, 2009; Koné et al, 2013), it was also found in what can be qualified as a waste of civilization such as used tires, discarded cans, car wrecks, etc.…”

“…Also, studies in Côte d'Ivoire have shown that urbanization is associated with a high abundance of Aedes larvae and a predominance of artificial containers as breeding sites, mainly colonized by A. aegypti , the main vector of these arboviral infections, in the city of Abidjan (Zahouli et al, 2017). Of note, this vector has a clear preference for anthropogenic sites over sylvatic sites (Guindo‐Coulibaly et al, 2019). Due to the increased risk of epidemic related to arboviruses, it appears necessary to define appropriate indicators to monitor and detect any outbreak of these viral infections.…”