Molecular Identification and Insecticide Resistance Status of Culex mosquitoes collected from blocked drainages in Lagos State, Nigeria

Abstract

Background: Culex mosquitoes are important vectors of several human pathogens causing infections such as lymphatic filariasis and several viruses. Poor and blocked drainage system can lead to impediment in water flow, leading to the artificial creation of larval habitats for Culex mosquitoes. Culex mosquitoes has the ability to breed in organically polluted water bodies and exhibit high resistance to insecticides. Therefore, this study assessed the species and insecticides susceptibility status of Culex breeding in blocked drainages in Lagos State. Methods: Culex mosquito larvae were collected from blocked drainages in three Local Government Areas (LGAs) of Lagos State, Nigeria, using standard WHO technique. The physicochemical parameters of the larval habitats were also recorded. Collected mosquito larvae were raised to adult, 2-3 days old. Glucose fed adults female mosquitoes were exposed to permethrin (0.75%) and DDT (4.0%) WHO insecticide test papers. Morphological identification was carried out using standard keys and molecular identification of Culex pipiens sub-species and kdr genotyping was carried out using PCR Results: High level of resistance was recorded with mortality r ate after 24 hour s for DDT ranging from 20% to 32% while permethrin ranges from 14% to 36%. The pH of the all the Culex mosquito larva habitats ranges from 7.38±0.11 to 7.62±0.29, while TDS ranges from 592.6±79.1 to 655±68.1. A total of 1113 Culex pipiens mosquitoes that were identify morphologically, some were selected for molecular identification using PCR assays, out of which 96.2% were identified as Culex p. quinquefasciatus while 3.7% were unidentified. Knockdown mutation (L1014F) was not detected in DDT and pyrethroids resistant Cx. quinquefasciatus in this study. Conclusion: Unplanned ur banization, inadequate w ater su pply and inefficient solid w aste and sewage management practices can result in the creation artificial larval habitats for Culex mosquitoes leading to potential outbreak of Culex mosquito borne diseases. The resistance to DDT and permethrin insecticides in Cx. quinquefasciatus in Lagos State may represent a threat towards the efficacy of ITNs and other forms of vector control such as indoor residual spraying in the future.