RESUMO
Background: Anopheles stephensi is the main vector of malaria in Iran. This study aimed to determine the susceptibility of An. stephensi from the south of Iran to bendiocarb and to investigate biochemical and molecular resistance mechanisms in this species. Methods: Wild An. stephensi were collected from Hormozgan Province and reared to the adult stage. The susceptibility test was conducted according to the WHO protocols using bendiocarb impregnated papers supplied by WHO. Also, field An. Stephensi specimens were collected from south of Kerman and Sistan and Baluchistan Provinces. To determine the G119S mutation in the acetylcholinesterase (Ace1) gene, PCR-RFLP using AluI restriction enzyme and PCR direct-sequencing were performed for the three field populations and compared with the available GenBank data. Also, biochemical assays were performed to measure alpha and beta esterases, insensitive acetylcholinesterase, and oxidases in the strains. Results: The bioassay tests showed that the An. stephensi field strain was resistant to bendiocarb (mortality rate 89%). Ace1 gene analysis revealed no G119S in the three field populations. Blast search of sequences revealed 98-99% identity with the Ace1 gene from Pakistan and India respectively. Also, the results of biochemical tests revealed the high activity of non-sensitive acetylcholinesterase, alpha and beta-esterase in the resistant strain compared to the susceptible strain. No G119S was detected in this study additionally the enhanced enzyme activity of esterases and acetylcholinesterase suggesting that resistance was metabolic. Conclusion: The use of alternative malaria control methods and the implementation of resistance management strategies are suggested in the study area.
RESUMO
Background: Malaria continues to be the main vector-borne disease in Iran. The endemic foci of malaria are in Sistan and Baluchistan Province, the borderline of Iran and Pakistan. By the year 2020 the program of the country is malaria elimination. The main vector control is using insecticide as Indoor Residual Spraying. The aim of the study was to evaluate the susceptibility of main malaria vectors to different insecticides recommended by WHO. Methods: All the insecticides papers supported by WHO and evaluation of insecticide resistance of Anopheles stephensi, Anopheles culicifacies, Anopheles superpictus to different chemical groups of imagicides including DDT 4%, malathion 5%, propoxur 01.%, lambdacyhalothrin 0.05%, deltamethrin 0.025% and permethrin 0.75% were followed by the WHO guideline. Results: Results of the susceptibility test against different insecticides revealed that An. stephensi and An. culicifacies are resistant to DDT and susceptible to other insecticides. An. superpictus is susceptible to all groups of pesticides. Conclusion: Knowledge on insecticide resistance in target species is a basic requirement to guide insecticide use in malaria control programmes in local and global scales.