Penetration of Host Skin by Cercariae of Schistosoma mansoni. I. Observed Entry into Skin of Mouse, Hamster, Rat, Monkey and Man

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Abstract
Behavior of cercariae of S. mansoni was observed and described on 10 skin types from mouse, rat, hamster" monkey and man. The percentages of cercariae penetrating, entry sites, and exploration and entry times were recorded. Early migration was followed wherever possible. Adult human and monkey skin and tail skin of haired mice were penetrated by over 85% of the applied cercariae; ear and body skin of adult hairless mice, body skin of adult hamsters and of 4- to 5-day-old mice, by 73-78%; body skin of 1- to 2-day-old mice and tail skin of adult hairless mice, by 65 and 62%; and body skin of 5-day-old rats, by 34%. Breaks, bends, angles and frank openings in the stratum corneum all featured in cercarial penetration. Entry sites of choice varied with the skin from wrinkle walls in human skin to hair follicles in tail skin of haired mice. Exploration times were related to the distribution of entry sites; entry times varied from 3 to 7 minutes, being shortest in 1- to 2-day mouse body skin and longest in adult human and hamster skin. Patterns of penetration and migration were similar on all the skins. Penetration involved orientation to the entry site, close oral attachment, great muscular activity, and copious glandular secretion. Migration was accomplished by a combination of muscular and glandular activity, with constant oral exploration until yielding intercellular avenues were encountered.