Transmission Potential of Lymphatic Filariasis Vectors in Selected Communities of Etim Ekpo Local Government Area, Akwa Ibom State, Nigeria: An Entomological Surveillance Study

Abstract

Background and Aims: Lymphatic filariasis (LF) remains a mosquito-borne parasitic disease for which entomological surveillance is important in assessing transmission potential. This study assessed the transmission potential of lymphatic filariasis (LF) vectors in selected communities of Etim Ekpo Local Government Area, Akwa Ibom State, Nigeria, based on mosquito species composition, physiological status and parity, and detection of Wuchereria bancrofti larval stages. Study Design: Community-based entomological surveillance study. Place and Duration of Study: Five selected communities in Etim Ekpo Local Government Area, Akwa Ibom State, Nigeria, from February to August 2024. Methodology: Adult mosquitoes were collected monthly during three dry-season months (February–April) and three rainy-season months (June–August). Mosquitoes were morphologically identified using standard identification keys. Female mosquitoes were assessed according to abdominal physiological status and parity. A physiologically selected subset of 479 female mosquitoes was dissected and examined for L1, L2 and L3 filarial larval stages. Mosquitoes containing any larval stage were classified as infected, while those containing L3 were considered infectious. Results: A total of 1,405 mosquitoes were collected, comprising Culex quinquefasciatus (393; 27.97%), Aedes aegypti (356; 25.34%), Anopheles gambiae (250; 17.79%), Culex pipiens (211; 15.02%) and Aedes albopictus (195; 13.88%). Female mosquitoes accounted for 756 (53.81%) of the total collection. Of these, 437 (57.80%) were parous and 319 (42.20%) were nulliparous. Of the 479 females dissected, none contained L1, L2 or L3 filarial larvae. The observed infection rate was therefore 0%, while the infectivity rate based on L3 detection was also 0%. Conclusion: Mosquito taxa potentially capable of supporting LF transmission were present in the study area, including a substantial proportion of parous females. However, no filarial larval stages were detected among the 479 females examined by microscopy. This zero-detection result applies only to the dissected sample and sampling period and does not establish the absence or interruption of transmission in the wider population. Continued surveillance, preferably complemented by molecular xenomonitoring, is recommended.