AEDES MOSQUITO ECOLOGY ALONG AN URBANISATION GRADIENT IN IBADAN, NIGERIA: PATTERNS OF OVIPOSITION, SPECIES COMPOSITION, AND IMPLICATIONS FOR ARBOVIRUS CONTROL
NJE Vol. 41(2): 108-122, 2025
DOI.10.36108/NJE/5202/14.0280
Ibrahim, Kolade T., Popoola Kehinde Olajide K., and Odaibo, Alex B.
Department of Zoology, University of Ibadan, Ibadan, Nigeria
Abstract
Aedes aegypti and Aedes albopictus drive the transmission of major arboviruses in West Africa, but their oviposition patterns and community structure across different levels of urbanisation in Nigeria remain poorly understood. To address this gap, ovitrap surveillance was conducted bi-weekly from July 2017 to April 2020 in Ibadan, southwestern Nigeria, covering four urban sites (Orogun, University of Ibadan, Samonda, and Ijokodo) and four semi-urban sites (Ojoo, Shasha, Idi-Ose, and Akingbile). Ovitrap positivity (OI) and egg density (EDI) were determined, and the collected eggs were subsequently reared to adulthood for morphological identification. A total of 6,558 ovitraps were deployed, of which 82.2% were recovered and 4,429 were positive, yielding 227,557 eggs. Ovitrap positivity varied across sites, with urban areas showing slightly lower but more variable values (74.5–83.1%) alongside higher egg densities (EDI = 57.5), whereas semi-urban areas recorded more consistent positivity (84.1%) but lower egg densities (EDI = 45.6). Urban areas were largely characterised by a strong dominance of Aedes albopictus (47.5%) and Aedes aegypti (38.8%). In contrast, semi-urban sites supported a more even mix, with Ae. aegypti (37.6%) and Ae. albopictus (36.1%) occurring alongside lower-density sylvatic species such as Ae. africanus, Ae. luteocephalus, and Ae. simpsoni. Species diversity and evenness were higher in semi-urban areas (Shannon H′ = 1.49; J = 0.76) than in urban areas (H′ = 1.20; J = 0.62). These findings demonstrate that urbanisation strongly influences Aedes ecology in Ibadan, with urban areas dominated by Ae. albopictus and characterised by higher egg production, creating conditions favourable for explosive arbovirus transmission, while semi-urban zones, with richer and more balanced assemblages including sylvatic species, may help maintain arboviruses between outbreaks. This study offers the first structured assessment of how oviposition patterns vary across an urbanisation gradient in Ibadan, underscoring the importance of adopting surveillance and control strategies that are tailored to local habitat transitions in order to effectively reduce arboviral transmission in fast-growing African cities.
Keywords: Aedes aegypti; Aedes albopictus; oviposition; urbanisation; arbovirus risk