Effect of house spraying with lambdacyhalothrin 10 per cent capsule suspension (CS) formulation in comparison with 10 per cent wettable powder (WP) against malaria vector in Malkangiri district, Odisha, India

BACKGROUND & OBJECTIVES: Selection of an insecticide and its appropriate formulation is a prerequisite of formulating any chemical control strategy against vectors. A hut scale field trial was carried out to study the effectiveness of house spraying with capsule suspension (CS) formulation of lambdacyhalothrin in comparison with its wettable powder (WP) formulation on mortality, density and behaviour of malaria vector in Malkangiri district, Odisha, India. METHODS: The two formulations were tested at 20 and 30 mg (a.i.)/m(2) for their effectiveness in terms of deterrence, excito-repellency, blood-feeding success, mortality and residual activity against Anopheles fluviatilis, the major malaria vector, in experimental huts in Malkangiri district, Odisha State, India. RESULTS: Both CS and WP formulations prevented the entry of An. fluviatilis in to the sprayed huts by >90 per cent for >6 months, the entire peak malaria transmission season in the area. The exit rate increased (90-99%) with different treatments and the feeding rate was reduced (91-97%). There was no significant difference between WP 30, CS 20 and CS 30 mg/m(2) in these respects. However, WP 20 mg/m(2) caused a lesser effect than the other three groups. The formulations or the dosages differed only in causing vector mortalities. Overall, the total mortality rate of An. fluviatilis was higher in the huts sprayed with CS 30 (58%) than the huts sprayed with CS 20 (48%), WP 20 (37%) and WP 30 mg/m(2) (47%). INTERPRETATION & CONCLUSIONS: Considering the duration of residual action and the effect on entry, exit, feeding and mortality of An. fluviatilis, the dosage 20 mg/m(2) of CS formulation of lambdacyhalothrin could be considered for further use.