Significance
Transmission of malarial parasites occurs via the bites of
Anopheles
mosquitoes, whose blood-feeding behavior modulates the risk of infection. In many malaria endemic regions, eradication strategies rely on reducing transmission by targeting nocturnal blood-feeding
Anopheles
with insecticidal nets. However, a proportion of mosquitoes may naturally feed when humans are not protected by nets, setting a ceiling to the efficacy of massive net-based interventions. In Bangui, Central African Republic, 20 to 30% of daily exposure to indoor bites occurs during daytime, and this fraction may correspond to mosquitoes escaping exposure to current vector control measures. Knowledge about the daily rhythmicity of mosquito biting is therefore crucial to adjust vector control tactics to protect people at places where they spend daytime.
Malaria remains the main cause of mortality and morbidity in the Central African Republic. However, the main malaria vectors remain poorly characterised, preventing the design of suitable control strategies. Here, we characterised the patterns and mechanisms of insecticide resistance in three important vectors from Bangui. Mosquitoes were collected indoors, using electrical aspirators in July 2016 in two neighborhoods at Bangui. WHO bioassays performed, using F 2 An. gambiae sensu lato (s.l.), revealed a high level of resistance to type I (permethrin) and II (deltamethrin) pyrethroids and dichlorodiphenyltrichloroethane (< 3% mortality). Molecular analysis revealed the cooccurrence of Anopheles coluzzii (56.8 %) and An. gambiae s.s. (43.2%) within the An. gambiae complex. Anopheles funestus s.s. was the sole species belonging to An. funestus group. Both kdr-w (40% of homozygotes and 60% of heterozygotes/kdr-w/wild type) and kdr-e (37.5% of heterozygotes) mutations were found in An. gambiae. Contrariwise, only the kdr-w (9.5% homozygotes and 85.7% of heterozygotes) was detected in An. coluzzii. Quantitative RT-PCR showed that CYP6M2 and CYP6P3 are not upregulated in An. coluzzii from Bangui. Analysis of the sodium channel gene revealed a reduced diversity in An. coluzzii and An. gambiae s.s. In An. funestus s.s., the pyrethroid/DDT GSTe2 L119F resistance allele was detected at high frequency (54.7%) whereas a very low frequency for Rdl was observed. Polymorphism analysis of GSTe2 and GABA receptor gene in An. funestus revealed the presence of one resistant haplotype for each gene. This study provides baseline information to help guide current and future malaria vector control interventions in CAR.
The chromosomal rearrangement 2La has been directly involved in the
ecological and deadly epidemiological success of the malaria mosquitoes
Anopheles gambiae and Anopheles coluzzii in sub-Saharan Africa. However,
little is known about the biological and ecological factors that drive
the local and temporal dynamics of this inversion in both species. Here,
we performed a year-round longitudinal survey in Bangui, Central African
Republic. We monthly sampled An. gambiae and An. coluzzii mosquitoes
indoor and outdoor using human landing catches for 48 hours non-stop. We
molecularly karyotyped all specimens to study the 2La inversion
frequency variations, and monitored the mosquito spatial and temporal
biting behavior throughout the year. In total, we successfully
karyotyped 5121 An. gambiae and 986 An. coluzzii specimens. The 2La
inversion frequency was higher in An. coluzzii than in An. gambiae
across the year. In An. gambiae and An. coluzzii, the inversion
frequency or karyotypes did not influence the biting behavior, either
location or time. Moreover, the inversion frequency variation in both
species was also independent of local climatic changes. Overall, our
results revealed that in Bangui, the 2La inversion segregates at
different frequency in each species, but this is not influenced by their
trophic behavior. Studying the impact of urban settings and the
population genetic structure of these two An. gambiae complex members
could bring insights into the intrinsic relationship between 2La
inversion and local conditions. More studies are needed to understand
the polymorphic equilibrium of this inversion in Bangui.
The chromosomal rearrangement 2La has been directly involved in the ecological and deadly epidemiological success of the malaria mosquitoes Anopheles gambiae and Anopheles coluzzii in sub-Saharan Africa. However, little is known about the biological and ecological factors that drive the local and temporal dynamics of this inversion in both species. Here, we performed a year-round longitudinal survey in Bangui, Central African Republic. We monthly sampled A. gambiae and A. coluzzii mosquitoes indoor and outdoor using human landing catches (HLC) for 48 h non-stop. We molecularly karyotyped all specimens to study the 2La inversion frequency variations, and monitored the mosquito spatial and temporal biting behavior throughout the year. In total, we successfully karyotyped 5121 A. gambiae and 986 A. coluzzii specimens. The 2La inversion frequency was higher in A. coluzzii than in A. gambiae across the year. In A. gambiae and A. coluzzii, the inversion frequency or karyotypes did not influence the biting behavior, either location or time. Moreover, the inversion frequency variation in both species was also independent of local climatic changes. Overall, our results revealed that in Bangui, the 2La inversion segregates at different frequency in each species, but this is not influenced by their trophic behavior. Studying the impact of urban settings and the population genetic structure of these two A. gambiae complex members could bring insights into the intrinsic relationship between 2La inversion and local conditions. More studies are needed to understand the polymorphic equilibrium of this inversion in Bangui.
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