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Permethrin resistance in the head louse Pediculus capitis from Israel
K Y Mumcuoglu1, J Hemingway, J Miller
1Department of Parasitology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Insights
Head lice (Pediculus capitis) in Israel show rapidly developing resistance to permethrin, a common insecticide. Susceptibility decreased fourfold between 1989 and 1994, indicating widespread resistance in head lice populations.
Area of Science:
- Medical Entomology
- Parasitology
- Public Health
Background:
- Head lice (Pediculus capitis) infestations are common in children.
- Permethrin, a pyrethroid insecticide, is widely used for head lice treatment.
- Reports of treatment failures with permethrin prompted an investigation into head lice resistance.
Purpose of the Study:
- To assess the level of permethrin resistance in head lice (Pediculus capitis) collected from children in Maale Adumin, Israel.
- To compare current resistance levels with historical data from 1989.
- To evaluate changes in susceptibility in a laboratory population of body lice (Pediculus humanus) for comparison.
Main Methods:
- Head lice were collected from 1516 children aged 3-12 years.
- Lice were exposed to permethrin-impregnated filter papers.
- Log time probit mortality (ltp) regression lines were calculated and compared between 1989 and 1994.
Main Results:
- A significant 4-fold decrease in permethrin susceptibility (at LT50) was observed in head lice between 1989 and 1994.
- The 1994 head lice population exhibited a more heterogeneous response to permethrin compared to the 1989 population.
- Laboratory body lice showed a non-significant increase in permethrin susceptibility over the same period.
Conclusions:
- Rapid development of pyrethroid resistance in head lice populations has occurred since permethrin's introduction in Israel.
- Increased resistance suggests a need for alternative or combination therapies for head lice control.
- Monitoring insecticide resistance in head lice is crucial for effective pediculosis management.
Abstract:
Head lice, Pediculus capitis, were collected from children aged 3-12 years in Maale Adumin, a town near Jerusalem, after reports of control failure with the pyrethroid insecticide permethrin. A total of 1516 children were examined: living lice and eggs were found on 12.1% of the children; or another 22.8% of the children only nits were found. Twice as many girls as boys (8.1% v 4%) were infested with lice and or nits. Head lice collected from infested children were exposed to permethrin impregnated filter-papers. Log time probit mortality (ltp) regression lines were calculated for mortality data and compared to ltp lines for a similar collection of head lice made in 1989. The regression lines for the two years were significantly different, with a 4-fold decrease in susceptibility at the LT50 level between 1989 and 1994. The slopes of the lines also suggested that the 1994 population was more heterogenous in its response to permethrin than the 1989 population. In contrast, a laboratory population of body lice (Pediculus humanus) tested with the same batch of permethrin-impregnated papers showed a slight but non-significant increase in susceptibility between 1989 and 1994. The results suggest that resistance to pyrethroids has developed rapidly among head lice since permethrin was introduced in 1991 as a pediculicide in Israel.