humaworm
Parasites live in the muscle tissue of both man and beast. Pork tapeworms for instance, live in the muscle tissue of hogs - BUT - when they are in humans, they get confused and go straight to the head area.
This is why all meat needs to be cooked. Not cooked to death - but cooked enough so that any parasites in the tissue will be killed. Regular bi-annual parasite cleansing will get rid of any that might have escaped the cooking process :)