Biodiversity Assessment of Mosquito Species in the Orashi Belt of Rivers State, Nigeria
By Wisdom U. G., Ebere, N., Ugbomeh A. P., Oghanri, S. U
A comprehensive mosquito survey conducted across five communities in the Orashi region yielded 1,768 specimens belonging to four genera: Culex, Anopheles, Mansonia, and Aedes, indicating a high overall vector density. Among these, Culex was the most taxonomically diverse genus, comprising Cx. quinquefasciatus (22.6%) and Cx. nigripalpus (22.4%), together accounting for 45% of all collected mosquitoes. Notably, Anopheles gambiae, the primary malaria vector, emerged as the single most abundant species, representing 35% of all specimens, highlighting its central role in sustaining malaria transmission in the region. Mansonia uniformis constituted 15% of the total, while Aedes albopictus was the least represented at 5%, reflecting its lower indoor-resting behaviour and potential seasonal variability. Spatial analysis revealed modest but meaningful differences in mosquito abundance across communities: Obite and Omoku recorded the lowest densities (18%), followed by Oboburu (19%), whereas Erema (22%) and Ahoada (23%) exhibited the highest densities. These patterns suggest localized ecological or anthropogenic factors favouring mosquito proliferation. Seasonal trends showed marked fluctuations, with abundance peaking in April (26%) and remaining high in March and September (21%), corresponding to periods of increased rainfall and humidity that enhance breeding conditions. Mosquito density declined steadily from October (18%) to November (11%), reaching its lowest level in December (3%) during the peak dry season. The mean biting rate of mosquitoes across sampled locations ranged from 2.24 to 2.70 bites per person per night. The highest mean bite rate was observed in Ahoada (2.70), followed by Omoku (2.50), Oboburu (2.39), Obite (2.32), and Erema (2.24). Monthly trends indicated peak biting in April (3.5), followed by March, with a progressive decline from September to December. These findings demonstrate clear spatial and seasonal variability in mosquito populations and biting activity in the Orashi region, underscoring the necessity for targeted, time-specific vector control interventions, particularly before and during peak transmission periods.