The residual effect of deltametrine in the control of malaria as observed on different types of walls in the Brazilian Amazon

RESUMO

The residual power of deltametrine FW (25mg l.a/m²) was evaluated and compared to that of DDT (2g i.a./m²) by means of biological tests. The different kinds of material used in constructing houses in Amazonia, such as masonry, wood, and wattle and daub, were used. Data from logistic regression showed that the drop in mortality, the inclination of the curve in relation to time, was similar for the two insecticides in the first samples. The negative coeficient for the variable, months after application, confirmed a reduction in the activity of both insecticides. Wooden and wattle walls showed positive and negative coeficiencies respectively from the beginning. The wooden walls retained a residual effect but the wattle walls were shown to be the least indicated for the application of insecticides. The experiments demonstrated a more prolonged residual effect for deltametrine as compared to DDT, and that insecticides work better on brick and cement and wooden walls than they do on wattle and daub constructions. For these reasons, it would be necessary to spray brick and cement walls every 8 months, wooden ones every 9 months and wattle constructions every 7 months to control the vectors of malaria