Tapeworm and B12

From http://www.aim4health.com/parasite.htm:

"Tapeworms are the largest of the worms; a beef tapeworm can grow up to 12 meters (39.3 feet) long! There are beef (Taenia saginata), pork (T. solium), fish (Diaphyllobothrium latum), and dog (Dipylidium caninum) tapeworms. A beef tapeworm does not produce marked symptoms, but can result in diarrhea, abdominal cramping, nervousness, nausea, and loss of appetite. Pork tapeworms can be dangerous. When the larvae migrate, they can invade the muscles, heart, eye, and brain. In the brain, they can produce seizures and brain deterioration. It is often misdiagnosed as epilepsy. Fish tapeworms are common in the Great Lakes area and Canada. They can be contracted by eating raw or lightly cooked freshwater fish. Fish tapeworms can consume 80% to 100% of a host's vitamin B12. Symptoms include nausea, anorexia, and pain or fullness in the upper abdomen."

Tapeworm, like other parasites, doesn't necessarily disappear even if one stops eating fish...