Diphyllobothrium latum (and other species) FAQs

What is Diphyllobothrium latum?

Diphyllobothrium latum and related species (the fish or broad tapeworm), the largest tapeworms that can infect people, can grow up to 30 feet long. Several other Diphyllobothrium species infect humans, but less frequently.

What are the signs and symptoms of Diphyllobothrium infection?

Most infections are asymptomatic. However symptoms can include abdominal discomfort, diarrhea, vomiting, and weight loss. Vitamin B12 deficiency leading to pernicious anemia may occur. Complications include intestinal obstruction and gall bladder disease caused by migration of proglottids.

What should I do if I think I might be infected?

See your health care provider.

How is infection with Diphyllobothrium diagnosed?

Diagnosis is made by identification of eggs or segments of the tapeworm in a stool sample with a microscope. Eggs are usually numerous, but more than one stool sample may be needed to find them.

Is medication available to treat infection with Diphyllobothrium infection?

Yes, safe and effective medications are available to treat Diphyllobothrium infection (praziquantel or niclosamide are used most often).

How did I get infected with Diphyllobothrium?

You got infected by eating raw or undercooked fish. Examples of fish include salmon, trout, perch, walleyed pike, and other species -- usually freshwater fish. Some fish such as salmon live in both fresh and salt water and can harbor Diphyllobothrium larvae. Lightly salted, smoked, or pickled fish also may contain infectious organisms.

Who is at greatest risk of infection?

Diphyllobothrium infection generally occurs in the Northern Hemisphere (Europe, newly independent states of the Former Soviet Union, North America, Asia), but has been reported in Uganda and Chile. Fish infected with Diphyllobothrium larvae may be transported to and consumed in any area of the world.