Synergized pyrethrin mousse, a new approach to head lice eradication: efficacy in field and laboratory studies

The purpose of this study was to evaluate the pediculicidal and ovicidal efficacy of a new, single-application formulation of synergized natural pyrethrins (presented in an aerosol mousse form) compared with an established, effective formulation based on permethrin (in a creme rinse form). The trial was a single-blind, comparative, randomized, parallel-group study. Children between the ages 7 and 15 years and adults with active head lice infections, identified by the presence of live lice, were enrolled from a school and a children's home in Dhaka, Bangladesh. Prevalence of infection ranged from 75% to 100% in the two study centers. The field study confirmed laboratory findings showing pyrethrin mousse to be effective at killing both lice and their eggs with a single 10-minute application. Of 52 patients identified with lice, 42 were treated with pyrethrin mousse and 10 with permethrin creme rinse. In each case, a sample of viable louse eggs was taken from the patients' hair before and after treatment. The eggs were then incubated to assess ovicidal activity. After treatment, the patients were examined for lice on alternate days until day 8 and then again on day 14. None of the patients in either group was found to have lice up to 2 days after treatment. One patient was found to have two moribund hatchlings on day 4. By day 6, when any eggs still present on the scalp would be expected to hatch, 19 pyrethrin mousse-treated patients were available for assessment. Two patients had been reinfected from contacts.(ABSTRACT TRUNCATED AT 250 WORDS)