Cercariae of Schistosoma mansoni and Plants: Attempt to penetrate Phaseolus vulgaris and Hedychium coronarium produces a Cercaricide

Abstract

DURING the development of a method for evaluating the penetration of the cercariae of Schistosoma mansoni¹, a large percentage of the larvae were observed to penetrate the skin of dead as well as living mice. In addition, many cercariae attacked isolated mouse tissue, as had previously been reported². Furthermore, similar numbers of cercariae entered the skin of a wide variety of rodents regardless of whether or not the animals were hosts within which the larvae could complete their life cycle³. It is well known that avian schistosomes penetrate mammalian skin where they die; in man this results in a severe dermatitis known as “swimmer's itch”⁴. Thus these organisms seem to be bereft of any discriminatory mechanism in their attack on mammalian tissues. In the plant kingdom, cercariae were observed to attempt to penetrate the integument of the green string bean, Phaseolus vulgaris, lose their tails in the process and thereby immobilize themselves. Investigation of eighty-one aquatic plants failed to reveal a similar penetration phenomenon, but resulted in the discovery of a cercaricidal substance which exuded from the cut stem of the white butterfly lily, Hedychium coronarium.