Background: Ae. aegypti is the vector of important μ arboviruses, including dengue, Zika, chikungunya and yellow fever. Despite not being specifically targeted by insecticide-based control programs in West Africa, resistance to insecticides in Ae. aegypti has been reported in countries within this region. In this study, we investigated the status and mechanisms of Ae. aegypti resistance in Niamey, the capital of Niger. This research aims to provide baseline data necessary for arbovirus outbreak prevention and preparedness in the country. Methods: Ovitraps were used to collect Ae. aegypti eggs, which were subsequently hatched in the insectary for bioassay tests. The hatched larvae were then reared to 3–5-day-old adults for WHO tube and CDC bottle bioassays, including synergist tests. The kdr mutations F1534C, V1016I, and V410L were genotyped using allele-specific PCR and TaqMan qPCR methods. Results: Ae. aegypti from Niamey exhibited moderate resistance to pyrethroids but susceptibility to organophosphates and carbamates. The kdr mutations, F1534C, V1016I and V410L were detected with the resistant tri-locus haplotype 1534C+1016L+410L associated with both permethrin and deltamethrin resistance. Whereas the homozygote tri-locus resistant genotype 1534CC+1016LL+410LL was linked only to permethrin resistance. The involvement of oxidase and esterase enzymes in resistance mechanisms was suggested by partial restoration of mosquitoes’ susceptibility to pyrethroids in synergist bioassays. Conclusion: This study is the first report of Ae. aegypti resistance to pyrethroid insecticides in Niamey. The resistance is underpinned by target site mutations and potentially involves metabolic enzymes. The observed resistance to pyrethroids coupled with susceptibility to other insecticides, provides data to support evidence-based decision-making for Ae. aegypti control in Niger.

: Recent dengue outbreaks have occurred in Ouagadougou and Bobo-Dioulasso, the two major cities of Burkina Faso. Dengue is a viral disease transmitted primarily by Aedes aegypti, a highly anthropophilic mosquito that thrives in human-transformed environments and breeds predominantly in artificial containers. In 2018, we investigated the resting and blood-feeding habits of Ae. aegypti in urban settings of Ouagadougou. In a 3-month cross-sectional study starting in August 2018, indoors and outdoors resting adult mosquitoes were collected using Prokopack aspirators in three health districts (HD). All mosquitoes were morphologically identified, and DNA was extracted from blood-fed Ae. aegypti females. A multiplex polymerase chain reaction with specific primers was used to identify the origin of the blood meal. A total of 4,256 adult Ae. aegypti mosquitoes, including 1,908 females, were collected. A preference for exophily was recorded in Bogodogo and Nongremassom, although an unexpectedly higher proportion of blood-fed females were found indoors than outdoors. Respectively, 96.09%, 91.03%, and 95.54% of the blood meals successfully analyzed in Baskuy, Bogodogo, and Nongremassom were from a single human host, with the remainder from domestic mammals as single or multiple hosts. Modeling total Ae. aegypti and blood-fed female counts showed that among other predictors, human density, outdoor environment, and house type affect their total densities. Our study revealed an exophilic tendency as well as a pronounced anthropophilic preference of Ae. aegypti adults, critical findings to consider when planning accurate entomological surveillance and effective interventions against Ae. aegypti in urban settings.

Malaria remains a major public health threat in Burkina Faso, as in most sub-Saharan Africa countries. Malaria control relies mainly on long-lasting insecticide-treated nets (LLINs) and indoor residual spraying. In Burkina Faso, an escalating of insecticide resistance has been observed over the last decades. This study aimed to investigate insecticide resistance and the underlying mechanisms in Anopheles gambiae complex in Ouagadougou. Anopheles gambiae s.l. larvae were collected from gutters and ponds, in Zogona, Tampouy and Tanghin, 3 localities in Ouagadougou from July to October 2018. The larvae were reared in the laboratory to adults stage and susceptibility profile to pyrethroid, carbamate, and organophosphate insecticides was assessed using WHO tube assays. Mosquito species and mutations linked with insecticide resistance, were identified through PCR. More than 95% of the collected An. gambiae s.l. were An. arabiensis. An. arabiensis displayed high resistance to permethrin and deltamethrin, with mortalities below 30%, but was fully susceptible to bendiocarb, fenitrothion, and malathion. A high-frequency of the pyrethroid resistance-associated kdr mutation 1014F (0.81) was recorded, while the frequency of 1014S mutation (0.18) was lower. However, the carbamate and organophosphate-associated Ace-1 119S mutation was not detected. Localities and breeding site type appear to influence pyrethroid resistance in the An. arabiensis population of Ouagadougou. The high resistance to pyrethroids in An. arabiensis of urban Ouagadougou is underpinned, at least in part by high-frequency kdr mutations. This result supports the switch to next-generation LLINs, in well-established pyrethroid resistance zones of Burkina Faso including Ouagadougout

In the absence of commercialized vaccines for most arboviruses, including dengue, chikungunya, and Zika, which are transmitted by Aedes aegypti, the management of vector populations to prevent disease transmission remains the cornerstone of arbovirus control strategies. Larviciding targets the early stages of the mosquito life cycle and subsequently reduces the capacity of adult population to transmit pathogens. Here, we report the susceptibility profile of Ae. aegypti larval populations from two West Africa cities, namely Niamey and Ouagadougou, to organophosphates larvicides. In Niamey, sampling was carried out using ovitraps at two sites, whereas in Ouagadougou, larvae were collected from three different types of larval containers at a single site. Temephos and fenitrothion were tested at six different concentrations each. Mosquito populations from Niamey and Ouagadougou were found susceptible to temephos and fenitrothion, with LD₅₀ < 0.015 mg/L and RR₅₀ < 5. However, Ae. aegypti populations from Ouagadougou showed reduced susceptibility to temephos compared to baseline data from 2016, as indicated by RR₅₀ values. This observation highlights the need for regular surveillance of larval susceptibility, as it may signal the emergence of temephos resistance in Ouagadougou. The acetylcholinesterase (AChE) mutation and the expression levels of metabolic genes Carboxy-/Cholinesterase (CCE) should be characterized to understand the molecular mechanisms underlying the observed phenotype response. Our results provide up-to-date data that could inform the potential deployment of these larvicides for the prevention and control of dengue and chikungunya outbreaks in Ouagadougou and Niamey.