Chapter 6 Human Head Lice: Status, Control and Resistance

摘要

Pediculosis, caused by Pediculus lice, is the most prevalent parasitic infestation of humans. Most people find lice intolerable and repeatedly and prophylactically apply pediculicides. Commercial pediculicides are limited and health providers are spending an increasing amount of time and resources dealing with infestations. Few alternatives exist when standard treatments fail. U.S.pediculicide sales were last estimated at >$150 million just for over-the-counter (OTC) remedies and overall cost of infestations is ～ $1 billion annually. Infestation rates range from 6-12 million cases annually with 2.6 million households affected and 8% of all schoolchildren infested. Louse resistance to most commercial pediculicides is now commonly reported and increasing in frequency, particularly to DDT, pyrethrins, pyrethroids, and malathion. Knockdown resistance (kdr) is a major factor worldwide in all pyrethrin/pyrethroid-resistant lice studied to date. Recent genotyping efforts have determined that kdr resistance is widespread but not yet uniform. Malathion (e.g., Ovide?) is prescribed most often when pyrethroids fail. However, U.S. lice have widespread but low levels of malathion resistance. Enhanced malathion carboxylesterase activity is a major mechanism associated with highly malathion-resistant lice from the U.K.