Molecular Profiling of Malaria Vectors Adapted to Toxic Petroleum Contaminated Ecosystems in Akwa Ibom, Nigeria Molecular Profiling of Malaria Vectors in Petroleum Contaminated Ecosystems
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Abstract
Petroleum pollution imposes ecological stress capable of altering malaria vector distribution and composition. Anopheles gambiae sensu stricto (s.s.), a principal malaria vector in Africa, belongs to the Anopheles gambiae complex, which comprises morphologically indistinguishable sibling species. Fixed X-chromosome differences separate An. gambiae s.s. into the Mopti (M) and Savanna (S) molecular forms, identifiable only using genetic markers. These forms exhibit differential adaptation to toxicologically stressed environments, potentially influencing local vector dynamics. Consequently, molecular tools are essential for accurate species and form identification. This study investigated Anopheles species adapted to petroleum-contaminated habitats in Akwa Ibom State, Nigeria, between March and November 2024. Larvae and pupae were collected from breeding sites in Eastern Obolo and Ibeno LGAs, reared to adults, and morphologically identified. Genomic DNA was extracted from individual mosquitoes and analyzed using Polymerase Chain Reaction (PCR) targeting the ribosomal DNA Internal Transcribed Spacer 2 (ITS2) region to confirm species complex membership and identify sibling species. Molecular forms of An. gambiae s.s. were determined using PCR–Restriction Fragment Length Polymorphism (PCR-RFLP). Physicochemical and hydrocarbon analyses of breeding-site water were also conducted. Hydrocarbon contamination was confirmed at all sites. All specimens belonged to the An. gambiae complex, with only An. gambiae s.s. and An. arabiensis detected. An. gambiae s.s. predominated (94.7%), and both M and S forms occurred sympatrically, with the M form dominant (80.3%). The dominance of An. gambiae s.s. and the Mopti form showed strong positive correlations with hydrocarbon concentrations, indicating hydrocarbon-driven selection. Persistent petroleum pollution appears to exert selective pressure favoring ecotoxicologically resilient Anopheles lineages, underscoring the importance of integrating molecular surveillance with environmental monitoring for effective malaria risk prediction.
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