This research work presents the malacological and schistosomiasis status in the Gharb, one of the large plains in northwestern Morocco, just before its redevelopment following the commissioning of a new and large dam, El Wahda. The results show that no danger was posed to humans by the populations of Planorbis metidjensis (Forbes, 1838) during the current study. In addition, an overlap of the distribution of schistosome infestation was monitored and the intermediate hosts raise several issues, notably: (1) the problem of the external or local origin of schistosomiasis in certain schistosomiasis foci in the Gharb plain; (2) a change, in time and space, in the geographical distribution of the intermediate host foci is possible; (3) a change in the infestation rate of the populations of the intermediate host is also possible; (4) Physa acuta (Draparnaud, 1805), the species whose presence is constant in schistosomiasis foci and which is experimentally infectable by Schistosoma haematobium (Bilharz, 1852) in the literature, may likely constitute a third vector of schistosomiasis in Morocco.