Abstract
BackgroundInsecticide resistance seriously threatens the efficacy of vector control interventions in malaria endemic countries. In Afghanistan, the status of insecticide resistance is largely unknown while distribution of long-lasting insecticidal nets has intensified in recent years. The main objective of this study was thus to measure the level of resistance to four classes of insecticides in provinces with medium to high risk of malaria transmission.MethodsAdult female mosquitoes were reared from larvae successively collected in the provinces of Nangarhar, Kunar, Badakhshan, Ghazni and Laghman from August to October 2014. WHO insecticide susceptibility tests were performed with DDT (4 %), malathion (5 %), bendiocarb (0.1 %), permethrin (0.75 %) and deltamethrin (0.05 %). In addition, the presence of kdr mutations was investigated in deltamethrin resistant and susceptible Anopheles stephensi mosquitoes collected in the eastern provinces of Nangarhar and Kunar.ResultsAnalyses of mortality rates revealed emerging resistance against all four classes of insecticides in the provinces located east and south of the Hindu Kush mountain range. Resistance is observed in both An. stephensi and Anopheles culicifacies, the two dominant malaria vectors in these provinces. Anopheles superpictus in the northern province of Badakhshan shows a different pattern of susceptibility with suspected resistance observed only for deltamethrin and bendiocarb. Genotype analysis of knock down resistance (kdr) mutations at the voltage-gated channel gene from An. stephensi mosquitoes shows the presence of the known resistant alleles L1014S and L1014F. However, a significant fraction of deltamethrin-resistant mosquitoes were homozygous for the 1014L wild type allele indicating that other mechanisms must be considered to account for the observed pyrethroid resistance.ConclusionsThis study confirms the importance of monitoring insecticide resistance for the development of an integrated vector management in Afghanistan. The validation of the kdr genotyping PCR assay applied to An. stephensi collected in Afghanistan paves the way for further studies into the mechanisms of insecticide resistance of malaria vectors in this region.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1149-1) contains supplementary material, which is available to authorized users.
Highlights
Insecticide resistance seriously threatens the efficacy of vector control interventions in malaria endemic countries
This study focused on target site resistance by assessing the presence of knock down resistance mutations in the voltage-gated channel gene using an allele specific polymerase chain reaction (PCR) approach previously developed for An. stephensi in India [17]
Whereas 90 % of An. superpictus are knocked down after less than 40 min in the presence of DDT in Badakhshan (KDT90 = 37.5 min, CI 95 % 3.548– 3.702), more than 50 % of An. stephensi or An. culicifacies mosquitoes seems unaffected by this insecticide after 80 min, with 50 % knock down time (KDT50) ranging from 100 to 230 min
Summary
Insecticide resistance seriously threatens the efficacy of vector control interventions in malaria endemic countries. The main objective of this study was to measure the level of resistance to four classes of insecticides in provinces with medium to high risk of malaria transmission. Malaria is a significant health problem in Afghanistan with more than eight million people still living in high transmission areas [1]. Malaria transmission is seasonal with the vast majority of cases recorded from June to November [2]. Plasmodium vivax accounts for 95 % and Plasmodium falciparum for 5 % of the malaria cases. In 2013, 39,263 confirmed malaria cases were recorded [1] and, in endemic areas, the prevalence of P. vivax is above 5 % [3].
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