Bionomics and Insecticide Resistance of Malaria Vector Mosquitoes in Lomami Province, Democratic Republic of the Congo

Background Malaria remains a major public health problem in the Democratic Republic of the Congo (DRC), particularly in Lomami Province. Understanding vector ecology, mosquito biting behavior, sporozoite infection rates, and insecticide resistance is essential for guiding malaria control and elimination strategies. This study was conducted to characterize the bionomics and insecticide susceptibility of Anopheles vector populations in Lomami Province. Methods An entomological study on mosquito bionomics was conducted in July and November 2024, corresponding respectively to the dry and rainy seasons, in the Mwene-Ditu and Kanda-Kanda health zones. Human landing catches (HLC), pyrethrum spray catches (PSC), polymerase chain reaction (PCR), and circumsporozoite enzyme-linked immunosorbent assay (ELISA-CSP) were used. Insecticide susceptibility tests were also carried out in January 2025. Comparisons were performed using chi-square (χ²) and Student’s t-tests, with the significance level set at p < 0.05. Results A total of 2,299 Anopheles mosquitoes were collected by HLC and 247 by PSC, dominated by An. funestus (45.02%) and An. gambiae s.l. (44.63%) (p = 0.78). An. funestus was significantly more abundant in Kanda-Kanda (p = 0.00000008), whereas An. gambiae s.l. predominated in Mwene-Ditu (p < 0.00000001). A seasonal alternation in species dominance was observed in Mwene-Ditu (p < 0.0001). Biting behavior showed a slight overall exophagic tendency (p = 0.06), although mosquitoes were more endophagic in Mwene-Ditu and more exophagic in Kanda-Kanda (p < 0.0001). The sporozoite index increased from 4.11% to 9.48% between July and November (p = 0.0007), while the entomological inoculation rate (EIR) increased from 1.46 to 2.09 infective bites per person per night (p < 0.001). Insecticide susceptibility tests revealed resistance to deltamethrin and DDT, but full susceptibility to bendiocarb and pirimiphos-methyl. Conclusion The findings indicate high vector activity and increased malaria transmission during the rainy season. The low level of preventive measures use, particularly long-lasting insecticidal nets (LLINs), combined with marked resistance to pyrethroids, highlights the need for continuous vector surveillance, insecticide rotation in malaria control interventions, and the promotion of appropriate protective behaviors to reduce mosquito bites.