Ortho-isopropoxphenyl methylcarbamate (OMS-33) as a residual spray for control of anopheline mosquitos. With special reference to its evaluation in the WHO programme for evaluating and testing new insecticides.

More than 1300 compounds have so far been included in the WHO Programme for Evaluating and Testing New Insecticides, which is designed to disclose compounds that may satisfactorily replace those to which insect vectors of disease have become resistant. The authors describe the successful passage of o-isopropoxyphenyl methylcarbamate (OMS-33) through the first 6 stages of the 7-stage programme that has been established for compounds intended for use against anopheline mosquitos and conclude that this product is suitable for testing in the final stage-large-scale epidemiological evaluation.In operational field trials (at 2 g/m(2)) OMS-33 has been shown capable of controlling Anopheles stephensi (in Iran), An. gambiae and An. funestus (in Nigeria) for 3-4 months, An. albimanus (in El Salvador) for 2-4 months and An. dthali (in Iran) for 2(1/2) months. It has an airborne effect by which anophelines are killed for a considerable time after OMS-33 has been sprayed, even though they do not make contact with a sprayed surface; this quality would appear advantageous in areas where anophelines enter houses and bite man but do not rest long enough on sprayed surfaces to acquire a lethal dose of insecticide or where significant outdoor biting occurs. The observance of simple safety precautions protects occupants of sprayed houses, spraymen and others from danger. Chemical studies have indicated that commercially produced water-dispersible powders of OMS-33 are stable under field conditions of storage and use.