Diphyllobothrium latum and related species (the fish or broad tapeworm), the largest tapeworms that can infect people, can grow up to 30 feet long. While most infections are asymptomatic, complications include intestinal obstruction and gall bladder disease caused by migration of proglottids. Diagnosis is made by identification of eggs or segments of the tapeworm in a stool sample with a microscope. Safe and effective medications are available to treat Diphyllobothrium. Infections are acquired by eating raw or undercooked fish, usually from the Northern Hemisphere (Europe, newly independent states of the Former Soviet Union, North America, Asia), but cases have also been reported in Uganda and Chile. Fish infected with Diphyllobothrium larvae may be transported to and consumed in any area of the world. Adequately freezing or cooking fish will kill the parasite.
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.
How can I prevent Diphyllobothrium infection?
Do not eat raw or undercooked fish.
The FDA recommends the following for fish preparation or storage to kill parasites.
o Cook fish adequately (to an internal temperature of at least 145° F [~63° C]).
o At -4°F (-20°C) or below for 7 days (total time), or
o At -31°F (-35°C) or below until solid, and storing at -31°F (-35°C) or below for 15 hours, or
o At -31°F (-35°C) or below until solid and storing at -4°F (-20°C) or below for 24 hours.