Effect of salivary CYP4EM1 and CYP4EM2 gene silencing on the life span of Chagas disease vector Rhodnius prolixus (Hemiptera, Reduviidae) exposed to sublethal dose of deltamethrin

Control of Chagas disease in endemic countries is primarily accomplished through insecticide spraying for triatomine vectors. In this context, pyrethroids are the first-choice insecticide, and the evolution of insect resistance to these insecticides may represent an important barrier to triatomine control. In insects, cytochrome P450s are enzymes involved in the metabolism of xenobiotics and endogenous chemicals that are encoded by genes divided into different families. In this work, we evaluated the role of three Rhodnius prolixus CYP4EM subfamily genes during blood meal and after deltamethrin exposure. CYP4 gene members were expressed in different insect organs (integument, salivary glands (SGs), midgut, fat body and malpighian tubules) at distinct transcriptional levels. CYP4EM1 gene was highly expressed in the SG and was clearly modulated after insect blood meal. Injection of CYP4EM1dsRNA promoted significant reduction in mRNA levels of both CYP4EM1 and CYP4EM2 genes and induced deleterious effects in R. prolixus nymphs subsequently exposed to sublethal doses of deltamethrin (3.4 or 3.8 ng/nymph treated). The higher dose reduced the survival over time and increased susceptibility of R. prolixus nymphs to deltamethrin. A better understanding of this mechanism can help in developing of more efficient strategies to reduce Trypanosoma cruzi vector transmission in Americas.

Susceptibility of phlebotomine sandflies (Diptera: Psychodidae) collected in the field, to alpha-cypermethrin in four municipalities endemic to leishmaniasis.

Although the chemical control against leishmaniasis began in 1953 in Brazil, little information is available on how this strategy has affected populations of phlebotomine sandflies in the field. The objective of this study was to analyze the susceptibility profile of four populations of phlebotomine sandflies to the insecticide alpha-cypermethrin. Sandflies collected in field in four Brazilian municipalities were evaluated using CDC bottles in different concentrations of alpha-cypermethrin. A total of 1,186 phlebotomine sandflies were used in the bioassays. The LD50 ranged from 1.48 to 2.57 ug/mL in the field populations. For a dose of 5 ug/mL of alpha-cypermethrin, the LT50 and LT95 ranged from 17.9 to 27.5 minutes, and LT95 from 39.7 to 61.5 minutes, respectively. All the populations studied were highly susceptible to the insecticide alpha-cypermethrin. Routine studies are needed to detect changes in sandflies susceptibility to insecticides.