End to lice? Effectiveness of new oral treatment demonstrated

This work has been published in the March 11th edition of The New England Journal of Medicine.

Lice are parasites which infest more than 100 million people worldwide each year. Children between the ages of 3 and 11 years are particularly vulnerable because of their social behaviour (games etc.) which is favourable to the propagation of parasites.

Although conventional anti-lice lotions are effective in a many cases, an ever increasing resistance to these treatments has been observed. Like many parasites, lice have evolved their own strategy for survival in difficult conditions. Through evolution of their genetic inheritance, they have become insensitive to the usual insecticides (malathion and pyrethrin) contained in the lotions. In the case of pyrethrin, mutations in the amino acids involved in the development of the sodium channels, acting at the central nervous system level of the lice, have been identified and are responsible for this resistance.

The appearance of new forms of resistance seems to be constantly increasing and lice epidemics are becoming ever more difficult to treat and eradicate. Hence the necessity to find new therapeutic alternatives.

A multi-centre international study

Researchers from AP-HP and Inserm have therefore performed a clinical trial to compare the effectiveness of a new oral treatment (oral Ivermectin administered at 400 μg per kilogram) with that of a conventional anti-lice treatment (0.5% malathion lotion). The trial was conducted by applying one or other of the products twice, at an interval of seven days, to 812 contaminated individuals from 376 families.

Ivermectin is a compound from the avermectin family which acts by blocking neurotransmissions in the brains of invertebrates.

The results obtained by the researchers are convincing: 95% of the 398 individuals who received Ivermectin were free from lice 15 days after the start of treatment, as compared to 85% of the 414 individuals treated with malathion. Ivermectin is already available on the market. It is prescribed, in particular, for treatment of scabies.

For Olivier Chosidow, coordinator of the study, no doubt remains, "When conventional treatments against lice do not work, taking Ivermectin twice, with a seven-day interval, offers excellent results and represents a real alternative to conventional anti-lice lotions."