According to the Merck Manual, three species of tapeworm may cause infections of the intestine in humans: beef tapeworm (Taenia saginata), pork tapeworm (Taenia solium) and fish tapeworm (Diphyllobothrium latum). These cause infections with adult tapeworms transmitted by raw or undercooked meat. Intestinal infections with tapeworms may be asymptomatic, but signs may include pain above the navel, nausea, hunger, weakness, weight loss, diarrhea, vitamin B-12 deficiency, anemia, anxiety or perianal discomfort when tapeworm segments emerge spontaneously from the anus.
B-12 Deficiency
Fish tapeworms absorb large amounts of vitamin B-12 and interfere with B-12 absorption from the terminal part of the small intestine (ileum), resulting in B-12 deficiency (this can also occur with beef and pork tapeworms).
Severity depends on the proximity of the tapeworm to the ileum, where B-12 absorption occurs. About 40 percent of people with tapeworms become B-12 deficient. Anemia may develop in people infected with fish tapeworm; this usually occurs in Scandinavian countries. Clinically, it resembles pernicious anemia and responds well to vitamin supplementation.
Weight Loss
According to TapewormDiet.net, the beef tapeworm secretes proteins that either speed up or slow down the human intestine, depending on the location of the protein in the digestive tract. The overall effect is less efficient food digestion. Since an average person ingests 2,000 Kcal a day, a 20 percent drop in efficiency would be 400 Kcal a day or 2,800 Kcal a week, which is approximately 1 lb. per week.
Tapeworm Segments
Usually, one tapeworm causes infection, but sometimes there may be as many as 10 infecting one human. According to Harrison's Principles of Internal Medicine, tapeworms attach to the intestine by hooks on the head. Behind the head are segments. As each segment matures, it moves away from the head as less mature segments are added. Some tapeworms may be several meters long. As the worm grows, some segments break off and are passed in feces, or may emerge spontaneously from the anus.
References
- Merck Manual: Tapeworm Infections
- Tapeworm Diet: FAQ
- "Harrison's Principles of Internal Medicine": Dennis Kasper, M.D.; 2005
