Increase of pediculicidal activity of commercial insecticides by combination with an artificial blend of faeces components.

Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae), the human head louse, is a parasitic insect responsible for pediculosis, a global health concern. In a previous study, we demonstrated that this hematophagous insect is attracted to a solvent extract from its faeces. In this study, we evaluated the head louse attraction towards mixtures of the three main components present in faeces (uric acid, hypoxanthine and guanine). A basic uric acid:hypoxanthine:guanine (10:10:1) mixture in 0.2 M produced significant attraction towards head lice in behavioural bioassays. In another approach, we evaluated the aggregation response of groups of head lice around collected fresh faeces and around the main components of the synthetic blend. In both studies, we found a significant aggregation of head lice. Finally, we studied the effect of the addition of the attractant blend on the mortality produced by malathion and permethrin, and found an increased mortality effect for both insecticides. We concluded that the blend of the main components of the louse faeces produces both attraction and aggregation of head lice, and increases the insecticide mortality effect of malathion and permethrin insecticides. These findings can contribute to the development of new strategies for pediculosis control.