Seasonal Abundance, Spatial Distribution, and Environmental Determinants of African Trypanosome Vectors in Two Protected Areas of Southwestern Nigeria

Abstract

Aims: This study investigated the seasonal abundance, spatial distribution, and environmental determinants of African trypanosome vectors (ATVs) in Omo Biosphere Reserve (OBR) and Oba Hills National Park (OHNP), southwestern Nigeria. Study Design: The study was conducted from November 2023 to August 2025 across dominant vegetation types in OHNP and OBR. In OHNP, sampling sites comprised secondary forest, savannah woodland, and riparian forest, while OBR sites included primary forest, secondary forest, and riparian forest. Methodology: Entomological surveys were conducted across major vegetation types using 24 Nzi traps set along a 1-km transect during wet (May–October) and dry (November–April) seasons. Relative humidity, altitude, temperature, and precipitation were recorded, and their associations with vector abundance were assessed using regression analyses. Results: Of 3,589 biting flies collected, 732 (20.4%) were ATVs, comprising three families, seven genera, and 15 species. OBR accounted for 57.9% of ATVs and OHNP 42.1%. Vector abundance was significantly higher during the dry season, with wet-season abundance reduced by 47.4% (β = 0.53, p < 0.001). Glossina spp. comprised 44.8% of ATVs, with 81.1% occurring in OBR. Relative humidity was negatively associated with vector abundance (β = 0.97, p = 0.004), whereas altitude showed a positive association (β = 1.01, p = 0.004). Conclusion: Abundance was highest in riparian forests of OBR and savannah woodland of OHNP. These findings highlight the importance of habitat-specific surveillance and integrated vector management for protecting biodiversity, wildlife health, and public health in protected ecosystems.