F o r   R e s e a r c h e r s

In seeking to understand a parasite, the basic biology of the host and the parasite are studied. Studying factors critical to their interaction underlies the interpretation of more complex studies. In this respect, basic study of head lice is well overdue. Human host factors, be they how various hair characteristics protect lice or how girls keep their hair, require serious study as much as the contribution of different fibre sizes in the sheep wool industry.

Some very comprehensive studies on human factors with regard to lice were published in parasitology journals a century ago. Researchers and editors of biological journals may be interested in looking again at this fascinating area of parasitology. It is time to take a more open approach to including the limited, but building, medical reports on pediculosis in parasitology discussions in order to piece together the host-parasite relationship and transmission dynamics.

A quick browse of entomology or veterinary parasitology journals shows that precise methodological tools have been developed to record the process of infection by parasitic insects or the basic physiological responses of animals. Of course the animal cannot be asked "When did you first notice the parasite attach to you; what attempts have you made to remove it; and, besides our tests, do you have any symptoms that indicate that the medication did not work?"

The health care profession may take the opportunity to jump in at this point and share with all those involved in the study of human lice, that clinical diagnosis in humans is complex and interesting because medicine is about the patient. Counting lice and pronouncing a cure falls short if the patient provides evidence of a persistent and distressing live infestation. Public health is all about helping as many people as possible reach their full potential.

The patient can provide further clues that may help with accurate diagnosis and appropriate treatment. History taking can reveal information that challenges the accuracy of louse counts, elucidates the length of the course of infection and contributes to the study of transmission and control of the parasite, which is important in understanding collective health.

From a health information-gathering perspective, louse-control policies should be based on more than just pure biological data. Human health encompasses well-being, not just an absence of disease or infirmity (WHO guidelines). Louse counts in point prevalence studies alone do not assess the impact on families and do not equate with effective community control. Low-level control fails to take into account the disruption caused by 'minor' outbreaks.

It is interesting that it has taken a recent aviation space medical study to enunciate the multiple problems of not screening for this communicable parasitosis upon entry into a close-contact community: "a symptom period of up to 9 weeks before a diagnosis was made", "three weeks of treatment were required to remove the infestation from all crew", and "treatment altered performance, comfort of crews, took time out of their duties, and even affected relations between crew members." -Lapierre J, Perreault M. Outbreak of head pediculosis during SFINCSS-99 isolation experiment. Aviat Space Environ Med 2002 Mar;73(3):203-5.

At present there is controversy over whether screening the "traditional" way (presumed to be confined to looking for eggs only) is the answer to control in schools, because some commentators suggest that children with extinct infestations will be overdiagnosed. On the other hand, fine-toothed combing requires extra logistic effort. Health care professionals often use tiered diagnostic tests. An initial screen may show up a marker that can indicate either current or non-active states of an infection and from there the patient must be followed up if a positive infection is not to be missed.

Entomologists understand that, with a keen eye, experience is quickly gained in spotting eggs. Medically, the eggs are a sign that may indicate either an inactive or active infestation and should serve as a precursor for further examination. Dry hair examination in school children to look for eggs near the scalp as a crude indicator (to sort non-infested from possibly infested cases) would be extremely quick and economically achievable. From there, assessing further dermatological signs, symptoms and history of infestation and treatment, and follow-up if any doubt, are second nature to the health professional who can make lightning-fast decisions that will in turn assist the individual and benefit the community.

There has been a building momentum in the gathering of information on this disease. The confirmation that head lice are of the same species as body lice solves part of a centuries-old argument and also raises questions about disease transmission. It is a good time now to look forward to interdisciplinary collaboration among scientists and health workers who should become more involved in a reassessment and a renewal of outlook on head lice research and health policy development.