All-Purpose Repellent Mixtures as Clothing Treatments against Chiggers

Abstract

of the serious annoyance these mites cause people in outdoor areas. The most desirable method of preventing attacks is to destroy the chiggers in their natural habitats by means of insecticidal sprays or dusts. However, this is usually impracticable or impossible because areas of infestation are generally too scattered and the number of persons affected is too small to justify the expense of area-control measures. Under certain conditions also, particularly in military operations, persons may be required to enter infested areas before such measures could be taken. In such cases reliance must be placed entirely on personal protection. The high incidence of scrub typhus (tsutsugamushi disease) in the Pacific theater of operation during World War II brought into prominence the need for effective methods of protecting military personnel from attacks by mites. Early tests at the Orlando, Florida, laboratory of the Bureau of Entomology and Plant Quarantine (Madden et al., 1944) demonstrated that the standard insect repellents, especially dimethyl phthalate, would prevent chigger attachments when applied to clothing. Just as the war ended benzyl benzoate was adopted by the Army as the standard material for treating uniforms. This material was shown (Snyder and Morton, 1946) to be effective through at least two soap-and-water washings, whereas dimethyl phthalate became ineffective after a single rinsing in cool water. The search for new and better clothing treatments for protection against chiggers, as well as against ticks, fleas, and mosquitoes, has been continued since 1944. Studies have shown that mixtures of several good repellents are effective against a wider range of species and on more persons than any one repellent used alone. For this reason a number of mixtures were tested against mosquitoes, ticks, fleas, and chiggers. From