RESUMO
Vector control largely relies on neurotoxic chemicals, and insecticide resistance (IR) directly threatens their effectiveness. In some cases, specific alleles cause IR, and knowledge of the genetic diversity and gene flow among mosquito populations is crucial to track their arrival, rise, and spread. Here we evaluated Aedes aegypti populations' susceptibility status, collected in 2016 from six different municipalities of Rio de Janeiro state (RJ), to temephos, pyriproxyfen, malathion, and deltamethrin. We collected eggs of Ae. aegypti in Campos dos Goytacazes (Cgy), Itaperuna (Ipn), Iguaba Grande (Igg), Itaboraí (Ibr), Mangaratiba (Mgr), and Vassouras (Vsr). We followed the World Health Organization (WHO) guidelines and investigated the degree of susceptibility/resistance of mosquitoes to these insecticides. We used the Rockefeller strain as a susceptible positive control. We genotyped the V1016I and F1534C knockdown resistance (kdr) alleles using qPCR TaqMan SNP genotyping assay. Besides, with the use of Ae. aegypti SNP-chip, we performed genomic population analyses by genotyping more than 15,000 biallelic SNPs in mosquitoes from each population. We added previous data from populations from other countries to evaluate the ancestry of RJ populations. All RJ Ae. aegypti populations were susceptible to pyriproxyfen and malathion and highly resistant to deltamethrin. The resistance ratios for temephos was below 3,0 in Cgy, Ibr, and Igg populations, representing the lowest rates since IR monitoring started in this Brazilian region. We found the kdr alleles in high frequencies in all populations, partially justifying the observed resistance to pyrethroid. Population genetics analysis showed that Ae. aegypti revealed potential higher migration among some RJ localities and low genetic structure for most of them. Future population genetic studies, together with IR data in Ae aegypti on a broader scale, can help us predict the gene flow within and among the Brazilian States, allowing us to track the dynamics of arrival and changes in the frequency of IR alleles, and providing critical information to improving vector control program.
Assuntos
Aedes/efeitos dos fármacos , Vetores de Doenças , Resistência a Inseticidas , Inseticidas/farmacologia , Aedes/genética , Aedes/fisiologia , Animais , Bioensaio , Brasil , Perfilação da Expressão Gênica , Técnicas de Genotipagem , Cobaias , Larva/efeitos dos fármacos , Malation/farmacologia , Mutação , Nitrilas/farmacologia , Piretrinas/farmacologia , Piridinas/farmacologia , Temefós/farmacologiaRESUMO
This study aimed to evaluate the effects of (g a.i. L-1) abamectin (0.02), carbaryl (1.73), sulphur (4.8), fenitrothion (0.75), methidathion (0.4), and trichlorfon (1.5) on the survival of larvae and pupae, on the oviposition of adults and hatching of eggs from treated Chrysoperla externa third-instar larvae from two different populations (Bento Gonçalves and Vacaria, Rio Grande do Sul State, Brazil). Morphological changes caused by abamectin to eggs laid by C. externa from Vacaria population were evaluated by mean of ultrastructural analysis. The pesticides were applied on glass plates. Distilled water was used as control. For the evaluation of larvae mortality, a fully randomized experimental design in a 2 x 7 (two populations x seven treatments) factorial scheme was used, whereas for the effects of the compounds on oviposition capacity and egg viability, a 2 x 4 factorial scheme was used. Carbaryl, fenitrothion, and methidathion caused 100 percent mortality of larvae. Abamectin reduced the hatching of eggs from treated third-instar larvae of both populations; however, this pesticide presented highest toxicity on insects from Vacaria. The ultrastructural analysis showed that abamectin caused malformations in micropyle and in chorion external surface of C. externa eggs. Based in the total effect (E), carbaryl, fenitrothion, and methidathion are harmful to C. externa; trichlorfon is harmless to third-instar larvae, while abamectin and sulphur are harmless and slightly harmful to third-instar larvae from Bento Gonçalves and Vacaria, respectively.
Avaliaram-se os efeitos de (g i.a. L-1) abamectina (0,02), carbaril (1,73), enxofre (4,8) fenitrotiona (0,75), metidationa (0,4) e triclorfom (1,5) sobre a sobrevivência de larvas e pupas, na oviposição de adultos e viabilidade de ovos de Chrysoperla externa de duas populações (Bento Gonçalves e Vacaria, Rio Grande do Sul). Alterações morfológicas causadas por abamectina em ovos depositados por C. externa da população de Vacaria foram avaliadas por meio de análises ultra-estruturais. Os agrotóxicos foram aplicados sobre placas de vidro. Água destilada foi utilizada como testemunha. Para avaliação da mortalidade de larvas utilizou-se delineamento experimental inteiramente ao acaso, em esquema fatorial 2 x 7 (duas populações x sete tratamentos) e para avaliação dos efeitos dos compostos sobre a capacidade de oviposição e viabilidade de ovos utilizou-se esquema fatorial 2 x 4. Carbaril, fenitrotiona e metidationa causaram 100 por cento de mortalidade das larvas. Abamectina reduziu a viabilidade de ovos de C. externa, provenientes de larvas de terceiro ínstar de ambas as populações; entretanto, apresentou toxicidade mais elevada sobre insetos de Vacaria. Análises ultra-estruturais evidenciaram que abamectina causou deformações na micrópila e na superfície externa do córion de ovos de C. externa. Baseando-se no efeito total (E), carbaril, fenitrotiona e metidationa são prejudiciais a C. externa; triclorfom é inócuo, enquanto abamectina e enxofre são inócuos e levemente prejudiciais a larvas de terceiro ínstar oriundas de Bento Gonçalves e Vacaria, respectivamente.