The tested plant is generally liable for the defect of the internal defence system (Augusto et al., 2017) hence the compatibility of the surviving snails to Schistosoma infection could be reduced. This reduction may be because the physiology of the snails would be altered due to constant exposure to the pumpkin seed extract (WHO, 2017). There is, however, no current motivation to trust that a common mechanism of action is responsible for these reactions (Labe et al., 2012). This then offers the proposition that there could be a range of activities and the mechanism of action of molluscicides might take time to be understood. Nonetheless, further research is necessary in order to discover the constituents responsible for the molluscicidal activity of pumpkin seeds so as to produce greater quantities for inclusive laboratory and semi-field bioassays.
 Our results show that the water and ethanol extracts of pumpkin seeds induced a significant molluscicidal activity. The results showed that there was no significant difference between the survival rates of juvenile and adult Biomphalaria snails exposed to water extracts (p = 0,208; CI = 95%). Pumpkin seeds water extract also had a molluscicidal activity against Bulinus snails. There was no significance in the difference of species exposed to the water extracts (i.e. Biomphalaria and Bulinus) (p = 0,665; CI = 95%. It was also observed that there was no significant dependence of mortalities on the time of the exposure of snails to the extracts. This observation was made for all the snail classes used in the study.
 
Acknowledgements
We thank Chinhoyi University of Technology Department of Biology for funding this work.

References