Head lice appearance and behaviour: implications for epidemiology and control

Abstract

Detecting Pediculus humanus capitis, the head louse, in human hair directly affects the diagnosis and control of head lice, pediculicide testing results and data collection for research purposes. Fine toothed combing is recommended as a diagnostic tool to improve visual detection and for the physical elimination of head lice. This study evaluated the effect of louse and host factors on the grooming process by observing the appearance and behaviour of the parasite and its recovery rate during simulated grooming experiments. It was found that detection and removal of lice were greatly influenced by the behaviour and morphology of the parasite, choice of grooming tool and several hair factors. These findings provide scientific explanation for broader clinical reports that undetectable louse numbers may be masked in the natural hair environment, thus affecting diagnosis and treatment and epidemiological surveillance. Inaccurate detection of head lice will flaw home assessments and has important implications for louse control. To overcome the inherent complexities in detecting head lice, screening of populations at risk should be conducted by experienced health professionals rather than lay persons.