Tapeworms, which are parasitic members of the flatworm class, or Cestoda, can cause quite a variety of problems for their hosts. Tapeworms can be found inside the intestines of a wide variety of warm-blooded animals.
Within the intestine, tapeworms can weaken the host by competing with it for nutrients. The scolex, or head, of some tapeworms has hooks or suckers, and can cause damage and inflammation of the intestinal wall. Large tapeworm infestations can cause intestinal bloackages.
In some cases tapeworms can move into other tissues aside from the digestive tract; this is referred to as cysticercosis. How serious the problem is is dependent on what tissues are infected. A tapeworm infestation of nervous tissue, known as neurocysticercosis, can be life-threatening of it involves brain tissue.