An Insecticide-Bait-Box Method for the Control of Sylvatic Plague Vectors

Abstract

Field trials were conducted in the San Francisco Bay region to test the effectiveness of 5 and 10% DDT powder in rodent bait-boxes against fleas on native wild rodents and in the rodent nests. The principal species concerned were known flea vectors of sylvatic plague, Malaraeus telchinum and Hystrichopsylla linsdalei, and the meadow vole, Microtus californicus, an important plague reservoir. Preliminary trials with the bait-boxes showed that Microtus and other small native rodents would enter them quite readily and feed upon rolled oats. About 90 g of either 5 or 10% DDT powder, placed on the floor boards of the bait-boxes, was picked up by the rodents and resulted in effective immediate control of all flea species. Residual control of all flea species on Microtus (with the possible exception of Hystrichopsylla linsdalei) was obtained over a period of several months. Analyses of Microtus nests showed considerable amounts of DDT which had been transported to them by the rodents. All flea species in nests were effectively controlled by 5% DDT for at least 132 days after the DDT was removed from the area.The field work was performed by Alva R. Kinney and Robert L. Martin. The fleas were identified by Harold E. Stark. The DDT analyses of rodent nests were done by the personnel of the Technical Development Laboratories, CDC, Savannah, Georgia, under the direction of J. A. Jensen.