Effectiveness and biochemical impact of ozone gas and silica nanoparticles on Culex pipiens (Diptera: Culicidae)

Culex pipiens (Diptera: Culicidae) is a vector of many serious human diseases, and its control by the heavy use of chemical insecticides has led to the evolution of insecticide resistance and high environmental risks. Many safe alternatives, such as ozone gas (O₃) and silica nanoparticles (silica NPs) can reduce these risks. Therefore, O₃ and silica NPs were applied to 3^rd larval instars of Cx. pipiens at different concentrations (100, 200, and 400 ppm) for different exposure times (1, 2, 3, and 5 min for O₃ and 24, 48, and 72 h for silica NPs). The activity of some vital antioxidant enzymes as well as scanning electron microscopy of the body surface were also investigated. A positive correlation was observed between larval mortality % and the tested concentrations of O₃ and silica NPs. O₃ was more effective than silica NPs, it resulted in 92% mortality at 400 ppm for a short exposure time (5 min). O₃-exposed larvae exhibited a significant increase in glutathione peroxidase, glutathione S-transferase, and catalase activities as well as the total antioxidant capacity. Scanning electron microscopy showing disruptive effects on the body surface morphology of ozone and silica NPs treated larvae. These results provide evidence that O₃ and silica NPs have the potential for use as alternative vector control tools against Cx. pipiens.