Seasonal dynamics and species diversity of Anopheles mosquitoes in malaria endemic districts of Southern Odisha India

Mosquitoes of the Anopheles, Aedes, and Culex genera are responsible for transmitting major vector-borne diseases. Malaria remains a significant public health concern in Odisha, primarily due to the state's conducive environment for Anopheles mosquito breeding. This study, conducted between March 2021 and February 2023 across 11 traditionally hyper-endemic districts in southern Odisha, aimed to assess seasonal variations in Anopheles diversity, composition, and abundance. A total of 10,807 Anopheles mosquito's species were collected manually indoors (house dwellings and cattle sheds) and outdoors (burrows, vegetation, tree holes, and culverts). Morphological identification revealed 18 Anopheles species. An. subpictus was the predominant species during the summer of 2021, with (328; 42.99%), and during the rainy season, with (1151; 46.60%), although its prevalence declined in subsequent years. An. culicifacies, a primary malaria vector, exhibited a consistent presence with (780; 31.58%) in the rainy season of 2021 and (798; 38.35%) in the rainy season of 2022. An. varuna remained scarce during summer and rainy seasons but peaked sharply in winter, with the highest prevalence in winter 2021-2022 (730; 35.56%) and winter 2022-2023 (485; 25.18%). Diversity indices (Shannon's, Simpson's, Pielou's) and Correspondence Analysis identified Ganjam as the district with the highest species diversity (1.26-2.2). Seasonal variation had a statistically significant impact on species diversity (p < 0.001), surpassing the influence of district level factors. These findings show that seasonality strongly influences Anopheles populations and highlight the need for localized, evidence-based vector control. Monitoring of mosquito diversity is vital for shaping malaria interventions suited to Odisha's transmission ecology.