Neurocysticercosis and cysticercosis are two very good reasons for not introducing tapeworm into the body.
These can cause epilepsy, blindness, heart failure and swelling of the brain.
In addition the tapeworm sucks all the goodness out of the food, leaving the person with a dire lack of vitamins, proteinns and nutrients. This could result in the 'pot belly' seen in starving people as well as thinning bones, anaemia and other medical complaints connected to poor diet.