The effect of larval exposure to plastic pollution on the major malaria vector, Anopheles arabiensis Patton (Diptera: Culicidae)

Abstract

Anopheles arabiensis is a dominant vector species of malaria within Southern Africa. Previous studies have demonstrated that Anopheles mosquitoes are capable of breeding in polluted water bodies, raising concerns about the role of environmental contaminants in vector biology. Among the most prevalent pollutants in aquatic environments is plastic. This study aimed to investigate the effects of plastic exposure on various biological factors of Anopheles arabiensis, including life history traits, insecticide tolerance, midgut microbiota composition, and epigenetic modifications. Larvae were exposed to artificially degraded disposable nappies, two plastic additives (Bisphenol-A and phthalic acid), and a representative of microplastics (commercially available latex beads). Two laboratory strains were used: an insecticide-selected strain (SENN DDT) and an unselected strain (SENN), allowing for the assessment of the effects of plastic exposure on insecticide resistance phenotypes. The results indicated that larval exposure to nappies and latex beads significantly delayed larval development in both strains. Conversely, exposure to plastic additives accelerated larval development in SENN but slowed it in SENN DDT. Adult longevity was significantly increased in SENN females exposed to nappies and BPA. An overall increase in tolerance to the insecticide deltamethrin was observed across both strains, with the most significant increase following phthalic acid exposure. Midgut microbiota analysis revealed greater shifts in SENN compared to SENN DDT following plastic exposure. Particularly, an increase in the abundance of pesticide and plastic-degrading bacteria was observed upon larval exposure to plastics. Additionally, strain-specific epigenetic changes were observed, with SENN males exhibiting higher histone acetyltransferase (HAT) activity post plastic exposure. Importantly, the effect of plastic exposure is contingent upon the specific insecticide resistance phenotypes present in An. arabiensis. However, further studies on the effect of plastics on wild populations of An. arabiensis are warranted as this will deepen our understanding of the real-world impact of plastic pollution on mosquito biology, insecticide tolerance, and vector-borne disease dynamics. This study enhances the understanding of the impact of pollution on the biology of An. arabiensis and underscores the role of plastic pollution as a potential contributor to the challenges encountered in vector control and malaria transmission. In conclusion, this research highlights the critical intersection of environmental pollution, vector biology, and public health, underlining the urgency of addressing and mitigating the challenges of pollution, especially as it pertains to malaria transmission and effective vector control strategies.