Entomological investigation of the 2023 chikungunya outbreak in Pouytenga, Burkina Faso, highlights the virus circulation in Aedes aegypti

---

Résumé

Dengue outbreaks have occurred in Burkina Faso since 2013, but the country experienced its first chikungunya outbreak in Pouytenga in 2023. Thus, a field investigation was undertaken to determine entomological risk factors associated with the chikungunya outbreak to inform decision-making and respond to the outbreak. Field entomological investigations were performed during the chikungunya outbreak in Pouytenga in September-October 2023. Adult mosquitoes were collected indoors and outdoors using Prokopack aspirators in selected households, while BG-sentinel traps were deployed in public places to assess mosquito density. The presence of chikungunya virus (CHIKV), dengue virus (DENV), yellow fever virus (YFV) and Zika virus (ZIKV) in Aedes aegypti was investigated by reverse transcription quantitative polymerase chain reaction (RT qPCR). Waterholding containers were screened for the presence of Aedes larvae and/or pupae and to determine traditional Stegomyia indices. Aedes mosquito eggs were also collected using oviposition traps, with the resulting adults used to assess susceptibility status to pyrethroid, carbamate and organophosphate insecticides. A total of 784 adult mosquitoes were collected using both BG-sentinel trap (n = 183) and Prokopack aspirator (n = 601). Aedes aegypti was the only species of Aedes collected and represented 16% (122/784) of all mosquitoes. Two out of the three pools of Ae. aegypti mosquitoes were positive for chikungunya virus while one pool was positive for dengue virus, representing minimum infection rates (MIR) of 48.8 and 24.4, respectively. Terracotta jars, drums/barrel and tyres were the most predominant and positive breeding sites. The house index (HI), container index (CI) and Breteau index (BI) were all over the threshold criteria for arbovirus risk. Aedes aegypti from the population showed resistance to deltamethrin and pirimiphos-methyl but were susceptible to malathion. Our results indicate a high risk of CHIKV and DENV infection in mosquitoes during the chikungunya outbreak in Pouytenga. We emphasise the need to implement sustainable entomological and epidemiological surveillance at sentinel sites for early detection of circulating arboviruses, along with intensified vector control measures to prevent outbreaks.

Mots-clés

Chikungunya, Dengue, Aedes aegypti, RT qPCR, Burkina Faso