Evidence of biological activity of Pulicaria crispa on Biomphalaria pfeifferi host snails of Schistosoma mansoni

The present study was carried out to investigate the molluscicidal activity of the herb Pulicaria crispa against the freshwater snails Biomphalaria pfeifferi, the intermediate host of Schistosoma mansoni parasites that cause intestinal schistosomiasis. It is an attempt to search for potential molluscicidal plants indigenous to Republic of Sudan. The molluscicidal activity of different parts of Pulicaria crispa (leaves, stems, and roots) on Biomphalaria pfeifferi snails in different periods of exposure (24, 48, and 96 hours) was studied. The assessment of toxicity was based on calculations of the lethal concentrations that killed 50% and 90% (LC50 and LC90) of the snail populations. Results revealed that leaves were the most potent against the snails (having the least LC50 and LC90 values) for all exposure periods (24, 48, and 96 hours), followed by flowers, and finally the stems. With regard to the effect of exposure time, it was evident that the prolongation of exposure period resulted in more potency of plant leaves against the snails as shown by the decreased LC50 and LC90 values for 96 hours exposure period, followed by 48 hours, and finally 24 hours. During the first five hours of exposure, snails showed sluggish activity, meanwhile dead snail remained inside their shells with blood around the shells. Accordingly, the herb Pulicaria crispa could be considered as one of the promising plant molluscicides in schistosomiasis control programs.