Journal of Vector Borne Diseases (Sep 2005)
Monitoring of insecticides resistance in main malaria vectors in a malarious area of Kahnooj district, Kerman province, southeastern Iran
Abstract
Background & objectives: Kahnooj district in south of Iran is an endemic area for malaria where Anophelesstephensi (Liston) is a main malaria vector and An. dthali (Patton) a secondary vector. According tothe national strategy plan on monitoring of insecticides resistance, this study was performed on susceptibilityand irritability levels of An. stephensi and An. dthali to different insecticides in the district.Methods: The susceptibility and irritability levels of field strains of An. stephensi and An. dthali at theadult and larval stages to discriminative dose of different imagicides was determined as recommendedby WHO.Results: Using discriminative dose and WHO criteria it was found that An. stephensi is resistant toDDT and dieldrin with 36.1 + 2.3 and 62.2 + 1.95 mortality rates, respectively; but susceptible to otherinsecticides. An. dthali was found to susceptible to all tested insecticides. The larvae of An. stephensi,exhibited 100% mortality for temephos and malathion, but 44 + 4.32 for discriminative dose offenitrothion. The results of irritability level for DDT and pyrethroids showed that permethrin had themost irritancy effect on An. stephensi and An. dthali. DDT and deltamethrin showed the least irritancyeffect against An. stephensi with 0.42 + 0.08 and 0.77 + 0.12 take-offs/min/adult, respectively, however,lambdacyhalothrin had the least irritancy effect against An. dthali with 0.096 + 0.02 take-offs/min/adult. The mean number of take-offs/min/adult with permethrin showed significant difference to DDT,lambdacyhalothrin, cyfluthrin and deltamethrin.Interpretation & conclusion: Pyrethroid insecticides are being used as indoor residual sprays in Iran.Based on our results, the main malaria vectors in the region are still susceptible to pyrethroid insecticides.Therefore, we propose the use of pyrethroids with low irritancy effect in rotation with carbamateinsecticides in two interval seasonal peaks of malaria transmission. Biological control including larvivorousfishes, using of local made Bacillus thuringiensis and larvicides such as chlorpyrifos-methyl arethe main larval control in the region. Result on larval test exhibited the susceptibility of main vectors tosome larvicides, although the 100% mortality was not obtained using fenitrothion and this is postulatedthe use of this insecticide in agriculture pest control. Monitoring and evaluation of insecticides resistancein malaria vectors in the region could provide an essential clue for judicious use of insecticides.
