Skin penetration of infective hookworm larvae. I. The path of migration of infective larvae of Ancylostoma braziliense in canine skin.

Migratory behaviour of Ancylostoma braziliense was studied in relation to the structure of the skin in dogs after primary infections. Data were obtained studying serial sections of lateral skin areas 6 mm in diameter, which had been exposed to larvae. The sections were stained either with Harris' haematoxylin and eosin or with P.A.S. or as outlined by Crossmon. Most of the larvae managed to penetrate the skin within 1/2 hr after the application. Hairs did not seem to constitute sites of entry. The larvae moved into the horny layer where edges of keratinized cells provide uneven spots. They migrated approximately parallel to the surface from the horny layer into the living epidermis and continued into an external root sheath of a hair follicle. They could only leave this site via sebaceous glands for the dermis or via apocrine sweat glands for the hypodermis. Tunnels from the epidermis into the dermis, however, suggested that a direct trans-epidermal migration had occurred. The vessels invaded by larvae were hypodermal lymphatic vessels. The first ones were found in these structures 1/2 h after the onset of the exposure.

Skin penetration of infective hookworm larvae. II. The path of migration of infective larvae of Ancylostoma braziliense in the metacarpal foot pads of dogs.

The hairless metacarpal foot pads of six hookworm-free puppies were exposed to infective larvae of Ancylostoma braziliense. Serial sections of the biopts stained with Harris' haematoxylin and eosin showed that the infective larvae are able to penetrate the toughest region of canine skin. Pores of eccrine sweat glands did not seem to constitute sites of entry and no larvae were detected in these glands. Larvae were only observed in the epidermis. The histopathology of the infected skin of the foot pads of the puppies was similar to that in human skin with "creeping eruption" as described by Fülleborn (1927). The biopts appeared to consist of hairy skin as well. In the unexposed adjacent hairy skin of the foot pads, larvae were also observed. They were found in the epidermis, hair follicle systems and dermis, suggesting that the migration from the epidermis into deeper tissue depends on the presence of the hair follicle systems.

Skin penetration of infective hookworm larvae. III. Comparative studies on the path of migration of the hookworms Ancylostoma braziliense, Ancylostoma ceylanicum, and Ancylostoma caninum.

The lateral skin areas of nine hookworm-free puppies were exposed to infective larvae of Ancylostoma braziliense, Ancylostoma ceylanicum and Ancylostoma caninum. Serial sections, stained with Harris' haematoxylin and eosin, showed that many similarities exist in the migration patterns of the hookworm species used. However, striking differences were observed between Ancylostoma braziliense on the one hand and Ancylostoma ceylanicum and Ancylostoma caninum on the other hand with regard to the speed with which the penetration occurred. Larvae of Ancylostoma braziliense may travel directly from the epidermis into the dermis--apart from migration via hair follicle systems--a path of migration we did not observe in infections with the other species used. Larvae of Ancylostoma braziliense seem to pass the skin more rapidly than those of Ancylostoma ceylanicum and Ancylostoma caninum. Many larvae of Ancylostoma ceylanicum managed to penetrate the skin 2--6 h after the onset of the exposure.