Permethrin-resistant human head lice, Pediculus capitis, and their treatment.
OBJECTIVE
To compare the pediculicidal activity of Ovide lotion and its active ingredient, 0.5% malathion, with Nix and its active ingredient, 1% permethrin, in permethrin-resistant head lice.


METHODS
In vitro pediculicidal product and active ingredient comparison. The presence of knockdown resistance-type mutations (T929I and L932F) was validated by DNA sequencing.


METHODS
University of Massachusetts-Amherst; University of Miami School of Medicine, Miami, Fla; Plantation and Homestead, Fla; and Mathis, Tex.


METHODS
Lice were collected in 3 geographical regions within the United States and in Yamburara, Ecuador, from healthy but infested individuals. Intervention Within 3 to 6 hours of collection, lice were given a blood meal, exposed to products or active ingredients, and observed at regular intervals.


METHODS
Percent mortality of lice at regular intervals after exposure to products or active ingredients and presence of T929I and L932F mutations.


RESULTS
South Florida lice exhibited a significantly slower mortality response to permethrin compared with susceptible Ecuadorian lice. Ovide and malathion killed permethrin-resistant lice faster than Nix or permethrin. The presence of T929I and L932F in permethrin-resistant south Florida lice was confirmed by DNA sequencing. The population of Texas lice from Mathis was slightly resistant to permethrin and included 13% with resistant genotypes.


CONCLUSIONS
The presence of the T929I and L932F mutations was confirmed by DNA sequencing in lice collected from children in south Florida that were resistant to the pediculicidal effects of permethrin and the leading permethrin-based head lice product, Nix. Malathion resistance was not observed in this study. The data also show that Ovide killed these same permethrin-resistant head lice approximately 10 times faster than permethrin or Nix.
Yoon
Kyong Sup
KS
Department of Entomology, University of Massachusetts-Amherst, MA 01003, USA.
Gao
Jian-Rong
JR
Lee
Si Hyeock
SH
Clark
J Marshall
JM
Brown
Leon
L
Taplin
David
D
D000818:Animals; D002648:Child; D005838:Genotype; D006801:Humans; D066298:In Vitro Techniques; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000627:therapeutic use*; D010373:Lice Infestations / Q000188:drug therapy* / Q000235:genetics*; D008294:Malathion / Q000627:therapeutic use*; D010374:Pediculus / Q000235:genetics*; D026023:Permethrin / Q000627:therapeutic use*; D010641:Phenotype; D012536:Scalp Dermatoses / Q000188:drug therapy* / Q000235:genetics*; D013997:Time Factors
D007306:Insecticides; D026023:Permethrin; D008294:Malathion