Malaria vector diversity, transmission and insecticide resistance in Island communities along the Volta lake in Southern Ghana

Introduction: Island communities along the Volta Lake in southern Ghana present unique challenges for malaria control, characterized by high transmission rates, limited vector control measures and geographically isolated. This study assessed the malaria vector diversity, seasonal abundance, transmission and insecticide resistance status of malaria vectors in these communities to inform effective control strategies. Methods: Mosquitoes were collected from three Island communities (Tuanikope, Allorkpem and Pediatorkope) using human landing catches, light traps and prokopack aspirators during the dry and rainy seasons. Morphological and molecular techniques were used to identify mosquito species, determine blood meal sources and detect insecticide resistance mutations. Sporozoite infections and entomological inoculation rates (EIRs) were also quantified. Results: A total of 25,092 mosquitoes from four genera were collected (Culicine = 88.14%, Anopheline = 8.94% and Mansonia = 2.92%). The Anophelines predominantly comprised Anopheles gambiae s.l. (1,911/2,243, 85.20%) followed by An. rufipes (249/2,243, 11.10%) and An. pharoensis (83/2,243, 3.70%). Indoor biting and resting densities were high across sites and seasons, with sporozoite-positive mosquitoes more frequently found indoors. Blood meal analysis revealed a strong anthropophilic feeding pattern (HBI = 80%). Annual EIRs ranged from 37.40 (ib/m/y) to 100.08 (ib/m/y). Low frequencies of insecticide resistance mutations (Vgsc-1014 F, Vgsc-1014 S, Ace-1 and Vgsc-1575Y) were observed. Conclusion: The study findings indicate high indoor biting and resting densities of Anopheles mosquitoes. High sporozoite rate along with low resistance mutation frequencies observed, emphasize the urgent need for continuous resistance monitoring and the implementation of targeted vector control strategies in these hard-to-reach Island communities.