Ivermectin acts as a posteclosion nymphicide by reducing blood feeding of human head lice (Anoplura: Pediculidae) that hatched from treated eggs.

TitleIvermectin acts as a posteclosion nymphicide by reducing blood feeding of human head lice (Anoplura: Pediculidae) that hatched from treated eggs.
Publication TypeJournal Article
Year of Publication2011
AuthorsStrycharz JP, Berge NM, Alves A-M, Clark MJ
JournalJournal of medical entomology
Volume48
Issue6
Pagination1174-82
Date Published2011 Nov
AbstractThe 0.5% ivermectin topical cream formulation was not directly ovicidal to treated eggs of head lice, as hatchability was not decreased. Nevertheless, the percent of hatched lice from treated eggs that took a blood meal significantly decreased (80-95%) compared with lice that hatched from untreated eggs and all treated lice died within 48 h of hatching, including those that fed. Dilutions of ivermectin formulation of 0.15 and 0.2 microg/ml, which were topically applied to 0-8 d old eggs, were not lethal to lice at 24 h posteclosion. However, 9 and 16% less lice fed when hatched from these treated eggs, respectively. Total [3H] inulin ingested by untreated first instars significantly increased over a 48 h feeding interval but was significantly less in instars that hatched from eggs receiving the 0.15 (36% less) and 0.2 (55% less) microg/ml ivermectin treatments compared with placebo. The reduced feeding that occurred after the 0.15 and 0.2 microg/ml ivermectin treatments occurred in the absence of mortality and suggests a unique mode of action of ivermectin on feeding that is separate from the mode of action of ivermectin leading to mortality. Failure of hatched instars to take a blood meal after egg treatments with formulated ivermectin is likely responsible for its action as a posteclosion nymphicide.
Alternate JournalJ. Med. Entomol.