Parasite

Demi Moore stars in this futuristic horror movie as Patricia Welles, a young woman struggling to get by in a post-apocalyptic world where a flesh eating parasite is terrorizing the city. When she meets up with Dr. Paul Dean, she learns the horrible secret behind the government's role in the creature's development and that Dr. Dean has an identical parasite feeding inside him. Determined to destroy the parasites, Dr. Dean and Patricia try to control the one inside him while they destroy the other before it gets too big and powerful to be stopped. (official distributor synopsis)