When he asked Rudy how long he had pretended to be Lois, the Parasite related his story to the Man of Steel. In his final moments he tells Superman that he still needed to have contact with Lois once every twenty-four hours to maintain his charade, confirming that she is still alive. He also told him that Lois loves him more deeply than he could ever know. The Parasite died before he could tell Superman where Lois was imprisoned. Lois was soon found alive by Superman and Batman inside a cave the Parasite had used as a hideout.
Lex Luthor, with whom it is implied the Parasite had engaged in amorous, "extramarital" activity while in Lois' form, was infuriated when he learned of the Parasite's schemes. As such, Luthor went to great efforts to obtain the Parasite's remains.
I feel a little sick after reading this.