Feeding and resting behaviours of natural Anopheles gambiae s.l. populations in an area of low malaria transmission in south-western Senegal: A comparative study between mainland and island settings.

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.