Compatibility of Biomphalaria alexandrina snails to infection with Schistosoma mansoni after exposure to sublethal concentrations of Myrrh.

The effect of exposing B. alexandrina to sub-lethal dose (LC10 & LC20) of Myrrh, on its susceptibility to infection with S. mansoni miracidia were determined. Starting three weeks post miracidial exposure, cercarial shedding was monitored. No shedding of cercariae were observed from snails treated with LC20. In snails treated with LC10, longer prepatent cercarial and shorter cercarial production periods than those of control group were recorded. The number of infected snails and of shedding cercariae were decreased. The study revealed that sublethal values of myrrh decreased the compatibility of B. alexandrina to S. mansoni infection thus playing an important role in the control of schistosomiasis.

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.