The penetration of human epidermal sheets by the cercariae of Schistosoma mansoni and the collection of schistosomula

Abstract

1. The percentage conversion of cercariae into schistosomula, when the former were penetrating human epidermal sheets, was found not to be significantly affected by the underlying media 1—5 (Table 1). The percentage conversion varied from 16·4% (in normal saline underlying skin) to 26.2 %. When distilled water was the underlying medium significantly fewer cercariae penetrated the sheets.2. There was a statistically significant decrease in the percentage conversion of cercariae to schistosomula when sodium chloride final concentration 0·67 % was placed in the exposure tube with the cercariae (1·6 % P = < 0·02 when compared with La Ye medium); 0·43 % sodium chloride also significantly decreased penetration.3. There was a statistically significant decrease in the percentage conversion of cercariae to schistosomula when the orientation of the human epidermis was reversed, i.e. the biologically inner surface was exposed to the cercariae (2.6 %, P = < 0.02, when compared with La Ye medium).4. Schistosomula agglutinated in the presence of normal or immune human serum or horse serum. In human serum to which donor red blood cells had been added, many red cells adhered to the schistosomula. The number adhering was less in inactivated serum. The adhesion was specific for red cells, the effect not occurring with either yeast cells or silicic acid particles. The red cells were shed from the surface of the schistosomulum after 4—12 h.I should like to thank the following: Dr S. A. Ibrahim, in whose laboratory this work was carried out; Dr S. Dawood of the Stack Laboratory, Khartoum for the use of his microscope; Mr T. R. Melrose and Mr J. R. Lauder for valuable discussions; the Medical Research Council, U.K., and the University of Khartoum for research grants. I am very grateful to the Pathology Department Faculty of Medicine, University of Khartoum, for preparing the sections of human epidermis.