Diphyllobothriasis is an infection caused by a fish parasite, also known as fish tapeworm. The infection is similar to the taenia solium and the taenia saginata, which contamination occurs through the ingestion of undercooked beef and pork. Humans are the definitive hosts, but other mammals such as dogs and cats that eat raw fish can serve as host.


The fish parasite is a worm scientifically called Diphyllobothrium latum, and represents one of the species of flat helminths (platehlminths) reaching the largest size among the helminths. Humans become infected when they eat raw or undercooked fish containing the worm larvae.

Incidence and risk factors

The infection is seen in many areas of Eastern Europe, North and South America, Africa and in some Asian countries. In Brazil, 27 cases were reported by the São Paulo State Health Office in the municipality of São Paulo, between March 2004 and March 2005, which took the Ministry of Health to issue a warning notice on the 7th of April 2005, thereby highlighting the potential infection hazards.


After the person, or any other host, consumes infected raw or undercooked fish, the larva grows in his/her intestine. The adult worm, which is segmented, may reach 30 feet in length with around 3,000 segments. The eggs are formed in each one of the segments and are passed still immature in the feces (up to 1,000,000 eggs each tapeworm). Occasionally, some segments (which are called proglottid) may also pass in the feces. The mature adult parasites lodging in the small intestine attack its mucous membrane.


The majority of infected individuals present no symptoms. Very heavy infections may include the following symptoms:

Abdominal discomfort
nausea, vomiting and diarrhea
loss of appetite and of weight
falta de apetite
massive infestation may cause intestinal blockage by the worms, leading to abdominal pain
this infection can lead to vitamin B-12 deficiency and, as a result, to pernicious anemia (megaloblastic); individuals with B-12 deficiency and anemia may suffer fatigue and confusion.


It is made through fecal smear, where the eggs can be seen through the microscope. Sometimes the segments (proglottid) pass in the feces, and can be visible to the naked eye. The blood test may reveal anemia.


If you suspect being infected, look for your physician or go to a health center for a previous diagnosis and further prescription.

Do not use any kind of medication without seeing a physician.


Infection can be eradicated with a single-dose treatment without any lasting effects.


Occurring infection with no proper treatment, anemia and intestinal obstruction by the worms may develop. But remember that the majority of the infected individuals do not present any symptoms.


A existência de diversos restaurantes que oferecem nos seus cardápios pratos como sushi, sashimi, ceviche, outros pescados crus, ou mal cozidos, nas suas preparações, possibilita o risco de contaminação ao consumidor se a matéria-prima estiver infestada.

Avoid eating raw or undercooked fishes. The consumers of raw or undercooked fishes are the high-risk group population for diphyllobothriasis. The existence of several restaurants offering dishes such as sushi, sashimi, ceviche, or any other kind of raw or undercooked fish in their preparation, represents a potential risk of contamination for the consumer if the raw material is infested.