The Effect of Larval Exposure to Plastic Pollution on the Gut Microbiota of the Major Malaria Vector <scp> <i>Anopheles arabiensis</i> </scp> Patton (Diptera: Culicidae)

Plastic pollution is prevalent in water bodies. However, most studies on plastic pollution focus on marine environments, with limited knowledge about its impact on freshwater ecosystems. This paucity of information extends to the effect on aquatic insects, with little reported data on the effect of plastic on malaria vectors. This is concerning as microplastics are reported to perturb the gut microbiota of culicine mosquitoes. This study examines how larval exposure to degraded plastic, plastic additives (phthalic acid, Bisphenol-A) and latex beads affects the gut microbiota of adult Anopheles arabiensis, with a comparison of the insecticide-unselected (SENN) and insecticide-selected (SENN-DDT) strains. The larval exposure had a minimal effect on alpha-diversity, but each plastic stressor altered beta-diversity in a non-strain-specific manner. Plastic-treated SENN showed an increase in unique bacterial genera. In contrast, untreated SENN-DDT displayed the highest abundance of unique genera, suggesting gut bacteria may play a role in mitigating the effect of plastic exposure in unselected strains. Additionally, larval plastic exposure increased bacteria associated with plastic degradation and pesticide metabolism. Although there was no significant change in Plasmodium-protective bacterial genera, inflammation-associated bacterial genera increased in both strains after treatment, suggesting potential immune modulation.