[Intra-domiciliary low volume spraying of malathion and deltamethrin for controlling Anopheles sp]

The effectiveness of low volume (LV) house-spraying of deltamethrin 0.027 per cent and malathion 20 per cent in the control of Anopheles sp was evaluated in two villages of Tabasco, México during the last semester of 1987. Two spray rounds were carried out at three-month intervals, using Fontan R-12 back-pack-space sprayers. Residual effect and cost-benefit were evaluated and compared to the standard DDT spraying technique using the Hudson X-pert sprayer. The entomological evaluation focused on mortality rates and density levels observed from intra and peridomicilliary man biting collections, indoor mosquito resting densities, curtain trap and the standard WHO wall bioassay. It was determined that when using the LV method these insecticides were highly effective. Malathion showed a residual effect of eight weeks whereas deltamethrin was found to have a residual activity of up to 12 weeks. Deltamethrin was more effective in reducing intra and peridomiciliary biting rates, and indoor resting mosquitoes. The cost-benefit ratio of deltamethrin and malathion LV house-spraying was 2.56 and 0.89, respectively, as compared to the standard DDT house-spraying. Considering its effectiveness in anopheline control and its cost-benefit, in addition to being a functional technique, intradomicile LV insecticide spraying should be considered as a practical alternative in malaria control programs.