Reduced susceptibility to selected synthetic pyrethroids in urban malaria vector Anopheles stephensi: a case study in Mangalore city, South India.
BACKGROUND
Synthetic pyrethroids are potent insecticides most commonly used in the vector control programme. These are applied for indoor residual sprays, space sprays and in impregnated bed nets. Resistance reduces the efficacy of insecticides. Thus, the susceptibility status of the target vector(s) is monitored routinely to select the effective ones. A study was undertaken in a malaria endemic coastal city Mangalore, Karnataka, South India, against the known malaria vector Anopheles stephensi.


METHODS
The susceptibility status was assessed at diagnostic doses of DDT (4%), malathion (5%), deltamethrin (0.05%), cyfluthrin (0.15%), alphacypermethrin (0.10%), lambdacyhalothrin (0.05%) and permethrin (0.75%) using the standard WHO tube test method during October/November 2006.


RESULTS
Anopheles stephensi was resistant to malathion by 54.9%, but tolerant to deltamethrin by 86.1%, cyfluthrin 95.5% and alphacypermethrin 90.6%, whereas it was susceptible to DDT by 98.1%, lambdacyhalothrin 98.6% and permethrin 100.0%, respectively. The KDT50 and KDT95 values for these insecticides also showed the similar responses.


CONCLUSIONS
Susceptibility of An. stephensi to DDT is an important finding as this has never been used in Mangalore city, whereas its rural counterpart Anopheles culicifacies is widely resistant to this insecticide. The study explores the selection and rotation of the appropriate insecticide molecule even within the same group for effective vector management.
Tiwari
Satyanarayan
S
National Institute of Malaria Research, ICMR Complex, Poojanahalli, Kannamangala Post, Devanahalli, Bangalore, 562110, Karnataka, India.
Ghosh
Susanta K
SK
Ojha
Vijay P
VP
Dash
Aditya P
AP
Raghavendra
Kamaraju
K
D000818:Animals; D000852:Anopheles / Q000145:classification / Q000187:drug effects* / Q000469:parasitology; D001681:Biological Assay; D007194:India; D007303:Insect Vectors / Q000145:classification / Q000187:drug effects* / Q000469:parasitology; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D007928:Lethal Dose 50; D008288:Malaria / Q000517:prevention & control* / Q000635:transmission; D009032:Mosquito Control / Q000379:methods*; D014505:Urban Population
D007306:Insecticides