Medical Encyclopedia


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Contents of this page:



Alternative Names    Return to top

Fish tapeworm infection

Definition    Return to top

Diphyllobothriasis is an infection caused by a fish tapeworm.

Causes    Return to top

The fish tapeworm, scientifically named Diphyllobothrium latum, represents one of the giant tapeworm species. Humans become infected when they eat raw or undercooked fish that contain tape worm larvae (sparganum).

The infection is seen in many areas where humans consume uncooked or undercooked fish from rivers or lakes. Diphyllobothriasis is seen in Eastern Europe, North and South America, African countries in which freshwater fish are eaten, and in some Asian countries.

After a person has eaten infected fish, the larva begin to grow in the intestine. The adult worm, which is segmented, may attain a length of 30 feet. Eggs are formed in each segment (proglottid) of the worm and are passed in the stool. Occasionally, a string of proglottids may be passed in the stool.

Fish tapeworm infection may lead to Vitamin B12 deficiency and the subsequent development of megaloblastic anemia.

Symptoms    Return to top

The vast majority of infected individuals have no symptoms. Symptoms may include:

Exams and Tests    Return to top

Infected individuals sometimes pass visible segments of worm in their stools.

Tests may include:

Treatment    Return to top

Medicines to fight the parasites are given in a single dose to treat the tapeworm infection. Vitamin B12 injections or supplements may be needed to treat megaloblastic anemia.

Outlook (Prognosis)    Return to top

Fish tapeworms can be eradicated with a single treatment dose. There are no lasting effects.

Possible Complications    Return to top

When to Contact a Medical Professional    Return to top

Call your health care provider if you have noticed a worm or segments of a worm in the stool. Also call if any family members have symptoms suggestive of pernicious anemia.

Prevention    Return to top

Avoiding raw freshwater fish and cooking fish sufficiently will prevent infection with the fish tapeworm.

References    Return to top

Sampaio JLM, Andrade VP, Lucas MC, et al. Diphyllobothriasis. Emerg Infect Dis. 2005;11:1598-1600.

Update Date: 8/16/2007

Updated by: Arnold L. Lentnek, MD, Division of Infectious Disease, Kennestone Hospital, Marietta, GA. Review provided by VeriMed Healthcare Network.

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