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Background Malaria remains a public health problem in many African countries. In Senegal, the Southern region had the highest malaria incidence and malaria-related deaths. The relationship between vector density and malaria transmission remains poorly understood in some specific areas. The aim of this study was to characterize the current entomological and transmission parameters with special emphasis on the Anopheles gambiae complex in the malaria pre-elimination area of Mlomp south-western Senegal. Methods The study was conducted from July 2020 to February 2021 in Djicomol and Cadjinolle in the commune of Mlomp region of Ziguinchor, Senegal. Sampling was carried out using Human Landing Catches (HLC) and Pyrethrum Spray Catches (PSC). Ovaries were dissected to determine female parity rate. Infection status, blood meal sources and species molecular identification were determined using Enzyme-Linked Immunosorbent Assay (ELISA) and Polymerase Chain Reaction (PCR) techniques respectively. Results A total of 6956 mosquitoes of the An. gambiae complex were collected, of which 6739 were by HLC (96.88%) and 217 by PSC (3.12%). The mean human biting rate was 36.98 bites/person/night (b/p/n) indoors and 43.25 b/p/n outdoors. Female biting activity was more frequent during the second half of the night. Mean parity rates were 24.83% indoors and 18.94% outdoors. The human blood index was estimated at 76.09%. Overall, An. gambiae sensu stricto ( s.s. ) was the most common species (75.08%). No female An. gambiae was found to be infected with Plasmodium falciparum in the sub-sample tested, thus no malaria transmission was recorded in Mlomp during the study period. Conclusions The results alert malaria control programme to develop additional strategies for controlling these vectors, which show exophagic behaviours to effectively combat malaria.

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. 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. 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 ), whereas no significant difference was observed for exophilic populations (P = 0.13). 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.