The effects of myrrh (Commiphora molmol) on the infected snails of Schistosoma sp. and their egg masses: effect on shedding of cercariae and on snail fecundity.

Myrrh has molluscicidal effect on infected Bulinus truncatus and Biomphalaria alexandrina snails at low concentrations (10 & 20 ppm respectively) after 24 hours exposure. The number of dead-snails increased with prolongation of exposure time. All Schistosoma free cercariae were killed by 2.5 ppm within 15 minutes. One day-old egg masses were more susceptible to the ovicidal effect of Myrrh than the five-day old ones. Both types of eggs were more resistant to the effect of Myrrh than the adult snails, embryogenesis began to stop at 20 ppm and eggs were all killed at 60 & 80 ppm. Shedding of cercariae of Schistosoma mansoni from infected B. alexandrina stopped at 1 ppm and was suppressed at 0.8 ppm. Snail fecundity decreased at 1 ppm.