Extended field trial of deltamethrin WDP for control of malaria at Jagdalpur, Madhya Pradesh, India.

The synthetic pyrethroid, deltamethrin 2.5% wdp, was evaluated at a dosage of 25 mg/sq m in a group of villages of tribal area around Jagdalpur, District Bastar (Madhya Pradesh). Study was carried out in three consecutive years from 1986 to 1988 with a total of five rounds of deltamethrin spray covering a population of approximately 10,000. The suspension of deltamethrin wdp was white in colour, odourless, non-irritant and the deposits were faintly visible on the surface of wall. A total of 3848 kg of 2.5% deltamethrin wdp was consumed during the trial. Insecticide was found effective in keeping the adult vector density An. culicifacies to a very low level for a period of 14-16 wks. Both anopheline and culicine mosquitoes were affected by the spray. The trial confirmed its long residual effectiveness from 15 to 16 wks on both mud and cement plastered surfaces. Deltamethrin spray shortened the average life span of vector mosquitoes. Observations indicated that insecticide although has an excito-repellent effect on mosquitoes, thus forcing exodus from treated area but with poor survival. Partial impact of deltamethrin spray was observed on the larval population confirm this. Deltamethrin spray did not exhibit any fumigant effect on mosquitoes. Significant decline in SPR from 17.93 to 4.26% was observed in areas sprayed with deltamethrin as compared to the comparison area. Similarly, SfR showed 81% reduction in experimental area while the control area showed increase by 42 per cent. No ill-effect of spray was noticed on the inhabitants, spray personnels, animal population and other non-target organisms of the area. The acceptability of the deltamethrin spray was found to be very high.