Triple insecticide resistance in Anopheles culicifacies: a practical impediment for malaria control in Odisha State, India

BACKGROUND & OBJECTIVES: In Odisha State, the control of malaria vectors has become dependent on synthetic pyrethroids, which are used for treatment of all approved long-lasting insecticidal nets (LLINs). The vast use of just one class of insecticide has led to the problem of resistance to insecticides in malaria vectors. One of the major malaria vectors in Odisha State is Anopheles culicifacies Giles. The aim of this study was to determine the resistance status of An. culicifacies to deltamethrin, a synthetic pyrethroid and other common insecticides used by the National Vector Borne Diseases Control Programme (NVBDCP) for indoor residual spraying in Odisha State. METHODS: Mosquitoes were collected during April 2014 - June 2014 from 15 randomly selected villages in five Plasmodium falciparum endemic southern districts of Odisha State. The blood-fed wild caught females were exposed to the diagnostic dosage of DDT (4.0%), malathion (5.0%) and deltamethrin (0.05%) for one hour. Mortality was recorded at 24 h after the exposure. RESULTS: Results indicated that An. culicifacies was resistant to all the three insecticides used in the malaria control programme in the five districts of Odisha State. INTERPRETATION & CONCLUSIONS: Resistance management strategy by appropriate rotation of different groups of insecticides including carbamates and incorporating a synergist with synthetic pyrethroids for treating mosquito nets should be considered for the control of malaria vectors in the area, especially where An. culicifacies is predominant. Periodical monitoring of susceptibility/resistance status of An. culicifacies to different insecticides is warranted.