CONICET | Buscador de Institutos y Recursos Humanos

The human head louse, Pediculus humanus capitis (Phthiraptera: Pediculidae), is an obligate ectoparasite that causes Pediculosis capitis and has been in contact with humans since the beginning of humankind. Head lice depend exclusively on the human scalp microenvironment which provides them with refuge, food and oviposition sites during their entire life cycle. Unfortunately, there is no information about the chemical communication that occurs when a louse interacts with its host. Host related cues have been widely shown to induce stereotyped behaviour in the parasites and epidemiological reports indicate the presence of differential levels of infestation among humans. Considering it, we proposed the hypothesis that human scalp compounds could modify the behaviour of head lice.In this work, we studied the effect of human scalp compounds on the behaviour of adult head lice. Filter paper segments were rubbed on volunteers scalps during 30 seconds and then were placed in the test arena. The movement of the insects was recorded using the software EthoVision®. Average movement parameters were calculated for the treatments in the bioassays such as total distance, velocity, frequency in the zone transition and time in each zone of the arena. We found that scalp compounds induced head lice to decrease average locomotor activity and to remain arrested on the treated paper. We also observed that head lice, in closeness with human scalp substances, performed behaviour presumably associated to the search for blood on the skin such as stillness, body raising perpendicular to the surface, and head disposition near the surface. Our results showed for the first time the effect of host compounds conditioning head lice behaviour. We discuss the role of these compounds in the dynamics of head lice infestation.

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