Lab experiments and field survey have been carried out to investigate the impact and the relationship between the exotic crayfish; Procambarus clarkii and Schistosoma and Fasciola vector snails in Egypt. In the Lab, several
species of freshwater snails, fish and aquatic plants were reported to serve as food for the freshwater crayfish. In the field, a survey for the crayfish and freshwater snails has been conducted at several irrigation channels in Qalyobiya,
Ismailia and Behera governorates, which had been previously surveyed during 1990s. The results of the experimental Lab indicated that the vector snails; Biomphalaria alexandrina, Bulinus truncatus and limnaea natalensis were the
preys of first choice for the crayfish. The field surveys showed high reduction and sometimes complete disappearance of vector snails in irrigation channels, which have been invaded by Procambarus clarkii, while in water courses which
do not harbor the crayfish, such as El Manayef drain and Fayed canal (West of Suez Canal), high densities of these vector snails were recorded. The present study is providing encouraging indication of the possible
overcoming schistosomiasis and fascioliasis in Egypt by the freshwater crayfish Procombarus clarkii.