A New Ivermectin Formulation Topically Kills Permethrin-Resistant Human Head Lice (Anoplura: Pediculidae)

Publication Type:Journal Article
Year of Publication:2008
Authors:J. P. Strycharz, Yoon, K. Sup, J. Clark, M.
Journal:Journal of Medical Entomology
Pagination:75 - 81
Date Published:Jan 2008
Keywords:human head louse, in vitro rearing system, ivermectin formulation

This study examines the effectiveness of a new ivermectin formulation for the topical treatment of the human head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae). Permethrin-resistant lice originally obtained from south Florida and maintained on an in vitro rearing system were 100% susceptible to ivermectin formulations by using a semiclinical hair tuft bioassay. The formulation was 100% effective at killing lice using 1, 0.5, and 0.25% ivermectin concentrations after 10-min exposures. As judged by the lethal time (LT)50 and LT95 values, 0.5% formulated ivermectin was 3.8 and 3.2 times faster at killing lice, respectively, than 0.5% nonformulated ivermectin, indicating that the formulation may facilitate the penetration of ivermectin into the louse. The hair tuft-based bioassay in conjunction with the in vitro rearing system provides a standardized method to assess the comparative efÞcacy of pediculicide formulations in a reproducible format that mimics the exposure scenario that occurs on the human scalp.

Short Title:J Med Entomol
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