Head lice and body lice: shared traits invalidate assumptions about evolutionary and medical distinctions

Human louse-borne diseases are reemerging overseas and biological study of their arthropod vector, Pediculus, is needed. In an observational study on head lice, morphological features on the surface of the human host and on closely associated personal objects, such as clothing, influenced location of lice. Given optimal conditions, head lice readily transferred to the body and clothing, fed on the 'naked' body, retreated into, and laid eggs in, clothing or body hair, from which viable nymphs hatched and in turn continued the life cycle. Both wild and colonised head lice developed and reproduced without scalp contact or hairs and withstood periodic separation from the host. Further, head lice elicited the same dermatopathological effects as are reported for body lice. The belief that only established body lice infestations are a public health threat is challenged; an alternative disease process is proposed; and further basic research into this parasite is strongly indicated.