Ecological considerations in scrub typhus. 3. Methods of area control.

The best of the known methods for control of the chigger vectors of scrub typhus is the application of dieldrin to the ground and low-lying vegetation as a fog or spray at the rate of 2.5 lb to the acre (28 kg/hectare). This has produced a more than 91% reduction in the numbers of Leptotrombidium (L.) akamushi (Brumpt, 1910) and L. (L.) deliense (Walch, 1922) for at least 2 years. Aldrin applied at the rate of 2.25 lb per acre (2.5 kg/hectare) is also highly effective, but less so than dieldrin. Lindane at the rate of about 5 lb per acre (5.7 kg/hectare) ranks third, but offers protection for only about 2 months. Because of the potential hazards to wildlife when such long-acting compounds are used, application of organophosphorous or carbamate insecticides may be used instead in areas where reapplication every few weeks is feasible. Fenthion and arprocarb are promising compounds for this purpose.