Those of you wondering just how long can parasites live in humans may be astounded by this. Parasites can actually live in us for up to 25 years. The tapeworm is the single most notorious parasite for such a long life inside its human host.During its lifetime, it can grow to 10 meters long. Flukes are other parasites that can comfortably inhabit the human body for periods of 10 to 20 years.During this time, flukes not only increase in numbers, but also move from the abdominal cavity to other organs. Such include lungs, the liver, kidneys and lungs.Flukes are known to grown up to 3.5 inches long.lukes are other parasites that can comfortably inhabit the human body for periods of 10 to 20 years. During this time, flukes not only increase in numbers, but also move from the abdominal cavity to other organs. Such include lungs, the liver, kidneys and lungs. Flukes are known to grown up to 3.5 inches long.