Influence of habitat characteristics and climate on Anopheles coluzzii breeding in urban Lagos Nigeria

Abstract

Malaria remains a major public health concern in Nigeria, where Anopheles mosquitoes are the primary vectors. Identifying ecological and
climatic drivers of larval habitats is crucial for developing targeted control strategies, particularly in rapidly urbanizing settings like Lagos
State. Larval surveys were conducted across six Local Government Areas (Ikorodu, Badagry, Ojo, Amuwo-Odofin, Kosofe, and Lagos
Mainland). Anopheles coluzzii larvae were collected using standard dippers and pipettes, morphologically identified, and confirmed to
species level by PCR. Physicochemical parameters of breeding water (pH, conductivity, total dissolved solids, oxidation–reduction potential,
and temperature) were measured in situ with a multimeter. Nineteen bioclimatic variables were obtained from the CHELSA database. Data
analysis included chi-square and t-tests for associations between habitat features and larval presence, correlation analysis, and Principal
Component Analysis (PCA). Of 18 breeding sites surveyed, 8 (44.4%) were positive for Anopheles larvae, all identified as Anopheles
coluzzii. Lagos Mainland sites harbored exclusively Anopheles coluzzii, while other LGAs showed mixed breeding with culicines. Small,
rainfall-fed puddles were the predominant positive habitats, though water appearance and physicochemical parameters were not significantly
associated with larval presence (p > 0.05). Bioclimatic analysis revealed significant correlations between larval presence and 12 variables.
The strongest predictors were Temperature Annual Range, Maximum Temperature of the Warmest Month, and Mean Diurnal Range (r > 0.8,
positive), while Precipitation Seasonality and Minimum Temperature of the Coldest Month showed strong negative associations (r > 0.75).
PCA identified two components explaining 90.2% of the variance, highlighting precipitation and temperature drivers. An. coluzzii
dominates urban Lagos larval habitats, with climate factors rather than local physicochemical conditions shaping their distribution. These
findings emphasize the need to integrate climate-informed surveillance with larval source management, including targeted larviciding and
environmental modification, into malaria control strategies.