Permethrin-resistant human head lice, Pediculus capitis, and their treatment

Area of Science:

• Entomology and Parasitology
• Dermatology
• Public Health

Background:

• Permethrin resistance in head lice (Pediculus humanus capitis) is a growing public health concern, diminishing the efficacy of widely used treatments.
• The T929I and L932F mutations are known genetic markers associated with permethrin resistance in head lice populations.

Purpose of the Study:

• To compare the efficacy of Ovide lotion (0.5% malathion) and Nix (1% permethrin) against permethrin-resistant head lice.
• To investigate the presence of specific resistance mutations in geographically diverse head lice populations.

Main Methods:

• In vitro testing of pediculicidal products and their active ingredients (malathion and permethrin).
• Head lice were collected from the United States and Ecuador.
• DNA sequencing was employed to validate the presence of T929I and L932F resistance mutations.

Main Results:

• Head lice from South Florida exhibited significantly reduced mortality rates when exposed to permethrin, confirming resistance.
• Ovide (malathion) demonstrated a faster kill rate against permethrin-resistant lice compared to Nix (permethrin).
• The T929I and L932F mutations were confirmed in permethrin-resistant lice from South Florida; Texas lice showed slight resistance.

Conclusions:

• The study confirmed permethrin resistance in South Florida head lice, linked to T929I and L932F mutations.
• Malathion resistance was not detected in the studied populations.
• Ovide (malathion) proved to be approximately 10 times faster in killing permethrin-resistant head lice than permethrin or Nix.