A Nonflammable Pyrethrum Spray for Use in Airplanes.

The increase of international travel by air has brought forth new problems in controlling the spread of quarantinable diseases. With specific reference to yellow fever, the destruction of infected Aedes aegypti on airplanes while in flight presents itself as one means of restricting the possible spread of this disease. In order to accomplish this end, however, it is necessary to have an agent which will kill these mosquitoes without hazard to human occupants of the airplanes. Pyrethrum in a kerosene base answers this purpose in certain respects; it is comparatively innocuous to human beings while at the same time lethal to Aedes in low concentrations. It has the disadvantage of being flammable. Recent observations I at the New Orleans quarantine station showed that only 2 to 4 grams per 1,000 cubic feet of a pyrethrum concentrate in kerosene (2 grams of pyrethrins per 100 cc) were lethal to Aedes when used as a fine spray. Since that time additional observations have been made at this station with pyrethrum in various and modified bases or vehicles with the object of developing a nonflammable mixture.