The control of mosquito vectors with insecticides is the most efficient tool to contain the transmission of pathogens, with spinosad biolarvicida being one of the most used control agents in the world due to its high toxicity to insects of different orders. In this regard, it is important to monitor the effectiveness of the product over generations to be able to target better control strategies. This study aimed to verify the resistance rate of Aedes aegypti submitted to selection pressure with larvicide spinosad under laboratory conditions, and to analyze the effects of this exposure on developmental and reproductive aspects. The selection was performed for six generations, with analyzes on the biological parameters of generations F2 and F6. The LC50 (0.036 mg/L) used in the tests increased in the F3 (0.114 mg/L) and F6 (0.101 mg/L) generations of the biolarvicide pressured population, with significant differences between F1 and F3 (p= 0.0019), and between F1 and F6 (p= 0.0187). However, there was no significant difference between F3 and F6 values (p> 0.05). The Resistance Ratio (RR) values obtained in this study (1.1; 1.3; 2.8; 3.2) were considered low. The mean time of the larval stage and the biological cycle of the population exposed to the biolarvicida were higher in F6 compared to the control population (p= 0.0001). The body weight of the females of the population exposed to the biolarvicida in the two conditions evaluated (before and after the repast) was lower than the control females (p= 0.0001). The oviposition rate of the females of the population exposed to the biolarvicida from F2 was low in comparison to the control population (p= 0.0001). However, even if the LC50 changes over the generations, the population is still considered to have a low level of resistance to the biolarvicide, according to the RR values and WHO parameters. Therefore, new experiments are needed to analyze the evolution of resistance in the laboratory. In addition, after six generations, spinosad negatively affected the mean larval stage and life cycle time A. aegypti, demonstrating that the insects of the pressured population took longer to develop. In addition, females body weight before and after the meal, as well as fecundity, were promptly reduced. Evidencing that larvicide affected reproductive aspects, which are related to the vector capacity of the species.
|
