Suscetibilidade de larvas de Culex quinquefasciatus a diferentes inseticidas

Abstract

RESUMOIntrodução: O presente estudo teve como objetivo avaliar a suscetibilidade de larvas de Culex quinquefasciatus a dois piretróides (Cipermetrina e Deltametrina), dois derivados da Avermectina (ivermectina e abamectina) e a um organofosforado (Temefós). Métodos: Larvas de 3 o e 4 o instares de C. quinquefasciatus foram expostas a diferentes concentrações destes (onze repetições) seguindo o protocolo da Organização Mundial de Saúde. Uma hora após a exposição, as larvas foram lavadas em água desclorada, transferidas para recipientes plásticos contendo água sem cloro, alimentadas e observadas por períodos de 24h, até se transformarem em adultos. Para a determinação das concentrações letais, os valores foram submetidos à análise de regressão usando o modelo probit pelo programa Minitab 15. Resultados: Diferenças entre as estimativas da CL 50 e CL 90 justificaram que a população de mosquitos testada apresenta heterogeneidade em resposta aos inseticidas, sendo a maior concentração utilizada para a CL 50 , a partir da análise de probit para o Temefós. Todos os inseticidas avaliados causaram mortalidade mais acentuada nas primeiras 24h exceto quando expostas à ivermectina. Conclusões: As larvas são suscetíveis a todos os inseticidas testados e há uma necessidade de um monitoramento dos inseticidas utilizados. Palavras-chaves:Culex. Inseticidas. Temefós. Piretróides. Avermectinas. ABSTRACT Introduction:This study aimed to assess the susceptibility of Culex quinquefasciatus larvae to two pyrethroids (Cypermethrin and Deltamethrin), two derivatives of Avermectin (Ivermectin and Abamectin) and an organophosphate (Temephos). Methods: Third-and fourth-instar larvae of C. quinquefasciatus were exposed to different concentrations of insecticides (eleven repetitions) according to the World Health Organization's protocol. One hour after exposure, larvae were washed in dechlorinated tap water, transferred to plastic containers containing water without chlorine, fed and observed for periods of 24h until reaching adulthood. To determine lethal concentrations, the obtained values were submitted to regression analysis using the probit model with the Minitab 15 program. Results: The highest concentration used for the LC 50 from probit analysis was for Temephos. The evaluated insecticides caused more pronounced larvae mortality in the first 24h with the exception of those exposed to ivermectin. Conclusions: This study demonstrates that larvae are susceptible to all tested insecticides and that there is a need for monitoring the use of insecticides.

RESPONSE OF Culex quinquefasciatus LARVAE TO THREE INSECTICIDES

“…In contrast to the study done in Brazil by ALVES et al. 1 in 2011 that showed temephos LC 50 was over 50 times higher than that presented in the actual study, while deltamethrin LC 50 was four times higher. However, ivermectin LC 50 was lower than 1/4 previous LC 50 and the curve presented lowest inclination, demonstrating higher heterogeneity in the response to this insecticide.…”

“…However, as also observed by ALVES et al 1 in 2011, probit analysis demonstrated that the highest concentration used was just the one used for deltamethrin. It is also observed that there are differences between insecticides, but temephos has a greater effect on mosquito larvae in lower concentrations, which for local populations of culicids meant no detection of insecticide resistance.…”

“…Aedes and Culex are part of the same subfamily of dipterans and not always the way to combat each one is distinguished. Thus, the types of insecticides and the doses to be employed against these dipterans should be corroborated for efficacy, in addition, some studies point out that the ivermectin can be an insecticide to be used against these insects 1 , 4 .…”

The Influence of Fatty Acid Methyl Esters (FAMEs) in the Biochemistry and the Na+/K+-ATPase Activity of Culex quinquefasciatus Larvae

“…The main limiting factor to control the population of C. quinquefasciatus and other insect vectors is their resistance to commonly used chemical insecticides. In Brazil, some studies indicate that C. quinquefasciatus populations are resistant to different insecticides (Alves et al 2011;Bracco et al 1997;Campos and Andrade 2003;González et al 1999;Yébakima et al, 1995 multiple products are being applied to control unwanted insect populations, with an unknown effect on the environment (Barreto 2005). For this reason, the demand for plant extracts and natural substances has grown as a natural alternative for combating the insect vectors as these substances are less toxic to the environment.…”

Larvicidal activity of oils, fatty acids, and methyl esters from ripe and unripe fruit of Solanum lycocarpum (Solanaceae) against the vector Culex quinquefasciatus (Diptera: Culicidae)

“…However, resistance to synthetic insecticides has recently become problematic in vector control programs. Thus is important the development of new products, with the capacity to prevent or minimize the resistance, to combat insects (1) . Biological products represent alternative approaches for preventing the development of resistance in mosquitoes.…”