Cheikh Lo

Anopheles arabiensis is a major malaria vector in Senegal, particularly in the Dakar region. The lack of a reference colony limits research on its biology and vector control. This study aimed to establish a stable An. arabiensis colony from urban populations in Keur Massar and Rufisque. Larvae were collected from 11 breeding sites and reared under controlled insectary conditions up to the F2 generation. Emergence rate, sex ratio, blood-feeding rate, and reproductive success were monitored. Species identification was performed morphologically and confirmed by PCR. Data were analyzed using R software, and differences between generations were assessed using Pearson’s chi-square test. Emergence rates in Keur Massar were 98.76%, 84.56%, and 85.15% for F0, F1, and F2, respectively, compared with 98.46%, 77.79%, and 86.22% in Rufisque. Females were most prevalent than the males, in both Keur Massar and Rufisque. In F2, blood-feeding rates reached 63.31% in Keur Massar and 90.91% in Rufisque. Eppendorf tubes inhibited oviposition, making group oviposition necessary for colony stabilization. PCR confirmed An. arabiensis. The study demonstrates the feasibility of establishing a stable An. arabiensis colony from Senegalese urban populations, providing a useful resource for future vector research and control strategies.

Malaria is a public health problem in Senegal, with heterogeneous transmission and little known about transmission drivers at the Senegalese border. This study aimed to determine bionomics of major vectors and malaria transmission in the Senegambian border. The study was conducted from July 2023 to March 2024 in Nemataba and Ndrame Ndimb (near the border), and in Medina Dianguette and Paoskoto (farther). Adult mosquitoes were collected using human landing catches and pyrethrum spray catches. Laboratory analyses were performed by Enzyme-Linked Immunosorbent Assay and Polymerase Chain Reaction techniques. Anopheles gambiae s.l. human biting rates (HBRs) were 1.05 bites/person/night (b/p/n) in Nemataba and 6.55 b/p/n in Ndrame Ndimb, while they were 14.73 b/p/n in Medina Dianguette and 1.47 b/p/n in Paoskoto. Anopheles funestus HBR was 2.88 b/p/n in Paoskoto and 0.37 b/p/n in Ndrame Ndimb. Human blood index for An. gambiae s.l. were 77.08% in Medina Dianguette, 66.67% in Nemataba, 2.42% in Ndrame Ndimb and 0 in Paoskoto, while for An. funestus they were 5.93% in Ndrame Ndimb and 3.65% in Paoskoto. Malaria transmission was detected in Medina Dianguette and Paoskoto, with 0.078 and 0.209 ib/p/n, respectively. This study highlights the diverse bionomic characteristics of major malaria vectors along the Senegambian border.

Background: The biting and resting behaviours of Anopheles species, which are human malaria vectors, are specifically linked to ecological and climatic requirements that characterize certain geographical settings, such as forests and humid savannah areas where favourable conditions for malaria mosquitoes are found. In southern Senegal, the outdoor resting behaviour of Anopheles gambiae s.l. populations is suspected to be a major problem in malaria control, given that indoor-based control tools are currently deployed across the country. A longitudinal study was conducted to investigate the population dynamics, trophic preferences and resting behaviours of Anopheles gambiae s.l. in mainland and island areas in south-western Senegal. Methods: Indoor and outdoor resting mosquitoes were collected from September 2020 to November 2021 using Pyrethrum Spray Catches and Prokopack aspirators, respectively. Field-collected mosquitoes were morphologically identified using conventional dichotomous keys, and in the laboratory, the mosquito blood meal source and molecular species identification were determined using enzyme-linked immunosorbent assays and polymerase chain reaction, respectively. Results: Out of 765 Anopheles collected, 181 were from the mainland, and 584 were from the island. Anopheles gambiae s.l. was the predominant species (91.1%), with seasonal variation. The indoor resting densities did not significantly differ ( P = 0.082) between the mainland (0.41 females per room) and island (4.09 females per room) areas. In mainland areas, the human blood index (HBI) was significantly greater ( P = 0.035) in indoor resting females (76.2%) than in outdoor resting females (47.6%), whereas in island areas, the HBI was generally lower, with no significant difference ( P = 0.51) between indoor (25.1%) and outdoor (31.1%) resting populations. Endophilic populations had greater HBIs in mainland areas than in island areas ( P = 2.63 × 10 ⁻⁵ ), whereas no significant difference was observed for exophilic populations ( P = 0.13). Conclusions: These findings provide a preliminary basic understanding of the feeding and resting behaviours of Anopheles gambiae s.l. populations in mainland and island areas for evidence-based malaria control programmes. Graphical