Ecdysteroids as regulators of host and parasite interactions: a study of interrelationships between Schistosoma mansoni and the host snail, Biomphalaria glabrata.

Ecdysteroids have been detected in trematode parasites and in several species of gastropod snails. The potential role of these and other hormones as regulators of host/parasite interactions is discussed. This study considers the role of ecdysteroids in the host parasite interactions between Schistosoma mansoni and Biomphalaria glabrata interactions. beta-Ecdysterone was found to be effective in stimulating host location activities in S. mansoni miracidia and in enhancing growth and egg production in B. glabrata. However, plant extracts rich in phytoecdysteroids were not attractive to miracidia and did not affect growth and egg production in snails. The potential role of ecysteroids in the process of parasitism and snail physiological processes is discussed. Plants rich in phytoecdysteroids do not appear to be of value in process which may interfere with the host parasite interactions in schistosomes.