An examination of the skin phase of schistosome migration using a hamster cheek pouch preparation

A living hamster cheek pouch preparation has been used to study the skin phase of schistosomulum migration. Between 0 and 16 h post-exposure schistosomula become increasingly difficult to see and lateral movement in the skin ceases. Up to 50 h post-exposure they remain poorly visible. They lie in fluid-filled lacunae within the epidermis, external to the basement membrane. The first schistosomula enter the dermis from 40 h post-exposure, approximately half having done so by 52.5 h. Coincidentally, they can be more easily distinguished from surrounding tissue. Up to 91% of original penetrants have been observed alive in pouch tissue at 65 h post-exposure. Since only 26% eventually mature in the hepatic portal system there would appear to be considerable attrition subsequent to the skin phase of migration. The mean diameter of venules penetrated was 22.7 micrometers and the mean time taken to penetrate was 8.01 h. The majority of schistosomula left the pouch between 60 and 80 h post-exposure.