Dr Michael Mosley explores the bizarre and fascinating world of parasites by turning his body into a living laboratory and deliberately infesting himself with them. He travels to Kenya to give himself tapeworm - a parasite that can grow to many metres inside the human gut. He also encounters lice, leeches and the deadly malaria parasite, before swallowing a pill-camera to reveal what's growing within him. By the end of his infestation Michael learns a new-found respect for these extraordinary creatures, which can live off and even take control of their hosts for their own survival