Phylogenetics and Cryptic Diversity Within the Simulium damnosum Complex in River Systems of South East and South South Nigeria: Implications for Onchocerciasis Elimination

The Simulium damnosum complex comprises multiple sibling species with differing vector competence for Onchocerca volvulus, the cause of river blindness. Effective onchocerciasis elimination in Nigeria requires knowing which cytospecies are present and biting in each river system, as vector control efficacy varies between siblings. Current cytotaxonomic data for river systems in South East and South South Nigeria are sparse and outdated relative to molecular methods now available. This study applies multi-locus molecular phylogenetics and cytotaxonomy to resolve cryptic diversity within the S. damnosum complex in eight river systems spanning Cross River, Akwa Ibom, Imo, Anambra, Rivers, Bayelsa, Edo, and Delta states. Larvae and pupae will be collected from selected rivers and processed for polytene chromosome inversion analysis and DNA extraction. Multi-locus sequencing of COI, ITS1, and 28S rDNA will construct a phylogeny calibrated against existing cytotaxonomy. Population genetic structure will be analyzed to assess dispersal boundaries between river systems. Infection rates with O. volvulus will be determined by real-time PCR for each cytospecies. This research makes an original contribution to blackfly taxonomy in Nigeria and provides the WHO African Programme for Onchocerciasis Control with species-specific transmission data essential for evidence-based elimination targeting. Keywords: Simulium damnosum complex, cytotaxonomy, onchocerciasis elimination, molecular phylogenetics, cryptic diversity