Fish tapeworm (diphylobotriasis)

THE diphylobotriasis it is a health problem which takes place in various parts of the world. In Brazil, until 2003, there were no records of the disease. With the increasing introduction of new cultures and the popularization of different eating habits, this disease, also known as “fish tapeworm”, has become more common.


Features

Diphylobotriasis is a disease caused by eating fish infected with the larva of a parasite of the genus Diphyllobothrium. Contaminated raw fish, undercooked, smoked at inappropriate temperatures or insufficiently frozen are responsible for the development of this parasitosis.

O parasite belongs to the phylum of flatworms, cestode class, order Pseudophyllidea, family Diphyllobothridae and gender Diphyllobothrium. It is one of biggest intestinal parasites of man, reaching even incredible 10 meters long. Another impressive data is the lifespan of the parasite, which can live up to 25 years.


Life cycle

THE "fish tapeworm" has two intermediate hosts, a crustacean of the copepod and fish group. Man becomes infected by ingesting fish with a parasite. In addition to humans, other mammals, such as dogs and cats, are definitive hosts of the parasite.

The ultimate host releases flatworm eggs into their feces. Embryos develop, giving rise to ciliated embryos, which hatch from eggs and are ingested by crustaceans. In the body of crustaceans, these embryos transform into larvae. The fish, when ingesting the crustaceans with the larvae, become contaminated. Man, by eating the fish, is also contaminated. The larva then migrates to the human intestine, where it develops, causing diphylobotriasis.

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Symptoms

Diphylobotriasis presents variable symptoms and signs in each case. Some people have an asymptomatic condition, but others have extremely severe clinical manifestations. Here are some of the possible clinical manifestations:

  • Diarrhea or constipation

  • vomiting

  • Anorexia

  • Weight loss

  • Weakness

  • abdominal discomfort

  • Flatulence

  • Eosinophilia (increased concentration of eosinophils in the blood)

  • Megaloblastic anemia (anemia caused by vitamin B12 deficiency)

  • Intestinal or bile duct obstruction when the patient has many worms


Diagnosis and treatment

Diagnosis is made by analyzing the patient's condition and with the aid of laboratory tests (stool analysis). The treatment is mainly done with praziquantel, an antiparasitic. In patients with megaloblastic anemia, administration of B-complex vitamins and folic acid is necessary.


Prevention

As the disease is contracted due to inadequate storage or consumption of raw foods of dubious origin, it is possible to prevent the disease with simple measures, such as:

  • Cook the fish well and avoid eating raw fish in regions where the problem is known to exist.

  • Only eat fish in places where hygiene conditions are known and which have authorization to operate.

  • Eat fish of known origin.

  • Freeze the fish at a temperature of -18ºC for 48 hours to kill larvae that may be in the animal.


By Ma. Vanessa Sardinha dos Santos

Would you like to reference this text in a school or academic work? Look:

SANTOS, Vanessa Sardinha dos. "Fish tapeworm (diphylobotriasis)"; Brazil School. Available in: https://brasilescola.uol.com.br/doencas/tenia-peixe-difilobotriase.htm. Accessed on June 27, 2021.

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