Penetration of mammalian skin by the infective larva ofNippostrongylus brasiliensis

Abstract

The behaviour of the third-stage larvae ofNippostrongylus brasiliensishas been studied on rat, mouse and human skin. Locomotion in thin films of moisture is by two-dimensional, undulatory propulsion on skin, and by three-dimensional, undulatory propulsion on hairs. In drops of water or in thick films of moisture locomotion is less efficient than in thin films. It is suggested that the thin film of moisture around larvae on the skin may become coated with a thin monolayer of lipid which could reduce evaporation from the surface of the nematode and from the film of moisture, thus extending the period before desiccation begins. Studies with the electron microscope have shown that the larvae move horizontally into the stratum corneum and later penetrate the epidermis and dermis by separating the constituent cells of these tissues. In the dermis there is dissolution of collagen around the larvae. It is suggested that this separation of cells and dissolution of collagen need not be brought about by enzyme action, as similar effects can be brought about by changes in pH or ionic composition of the bathing medium.