DE won't cure an infestation and I'm not sure it does a lot to control numbers. Permethrin/pyrethrin dusts and sprays are an alternative to Sevin 5% garden dust. Permethrin/pyrethrin is available as garden dust or spray, Adam's (or other brands) flea and tick spray, and "poultry dust" type products in feed stores. DE is primarily a dessicant for feed, and is used against soft bodied insects (caterpillars, etc.) in the garden, also dries the litter, thus deodorizing.