Echinostoma liei (Jeyarasasingam, Heyneman, Lim and Mansour, 1972), was used for the first time as bio control agent for  the wild rat Rattus  rattus  frugivorus Rafinesque . Two levels of infection were used (250 and 500 metacercariae / rat ) and histopathological  alterations were studied in the  affected organs ( intestine ,liver  and testis )  . The investigation revealed that high infection of E. liei resulted in severe pathological alteration in rat intestine, and liver, such as edema, lymphocytic infiltration, necrosis and   hemorrhage in the liver lead to death in addition to testis hypertrophy with seminiferous tubules devoid of spermsthatmay lead to sterility.  Thus, E. liei could be considered a new effective  biological agent  for controlling wild rats causing either death or sterility  and also  safe to human  since  people in Egypt don't eat fresh water snails either raw or cocked ).