Diphyllobothriasis: Causes, Symptoms, Diagnosis and Treatment

Diphyllobothriasis is an fish-borne parasitic caused by tapeworms (Diphyllobothrium latum) that can affect humans and other animals.

In this article, we will discuss the causes, symptoms, diagnosis, prevention and treatment for diphyllobothriasis.

Image: Diphyllobothriasis symptom (abdominal pain).

Causes of Diphyllobothriasis Disease

Diphyllobothriasis is caused by the fish tapeworm Diphyllobothrium, which is found in freshwater fish such as salmon, trout, and pike. The infection occurs when a person ingests raw or undercooked fish that contains the tapeworm’s infective larvae.

In some cases, the infection can be acquired through consumption of raw or undercooked fish in sushi, ceviche, or other dishes popular in some cultures.

Another way of becoming infected is by consuming water from lakes, rivers, or streams that are contaminated with tapeworm larvae, this is not common but it’s possible, especially in areas where sanitation is poor.

What is Diphyllobothrium latum

Diphyllobothrium latum, more commonly known as the fish tapeworm, is a species of parasite that can infect humans.

The tapeworms are commonly found in parts of Europe, North America, and Asia where freshwater fish are consumed raw or undercooked.

The adult worm lives in the small intestine and attaches itself to the intestinal wall by its suckers and hooks.

It then begins to consume nutrients from food passing through the intestines while releasing eggs into feces that can contaminate water sources such as lakes and rivers if not disposed of properly.

If left untreated, the infection can cause deficiencies in vitamins B12 and folate which can lead to anemia.

Life Cycle of Diphyllobothrium latum

The life cycle of Diphyllobothrium latum includes the following stages:

Egg: The tapeworm releases eggs into the host’s feces, which then enter freshwater or brackish environments.

Coracidium: The eggs hatch into a free-swimming larvae called a coracidium in freshwater or brackish environments.

Procercoid: The coracidium is then ingested by a copepod, a small aquatic crustacean. Inside the copepod, the larvae develops into a procercoid.

Plerocercoid: The procercoid is then ingested by a fish, where it develops into the plerocercoid stage.

The plerocercoid develops into the adult tapeworm in the small intestine.

Adult tapeworm: The adult tapeworm lives in the small intestine of the human host, where it attaches to the intestinal wall and absorbs nutrients. The tapeworm can grow up to 30 feet in length.

It’s important to note that the life cycle is not completed until the human host excretes eggs in feces and the cycle starts over again.

Diphyllobothriasis Signs & Symptoms

The signs and symptoms of diphyllobothriasis, an infection caused by the fish tapeworm Diphyllobothrium, can vary depending on the number of worms present and the duration of the infection.

Some common symptoms include:

  • Abdominal pain and discomfort
  • Diarrhea
  • Nausea and vomiting
  • Weight loss
  • Anemia (due to vitamin B12 deficiency)
  • Fatigue
  • Weakness
  • Abdominal distension
  • Loss of appetite
  • In some cases, patients may also have visible segments of the tapeworm, called proglottids, in their stool or around their anus.

It’s important to note that many people with this parasite may have no symptoms at all. And some symptoms can be mistaken for other illnesses, making it hard to diagnose.

Diphyllobothriasis Diagnosis

Clinical examination: Symptoms such as abdominal pain, diarrhea, and weight loss may suggest the presence of a tapeworm infection.

Stool analysis: A sample of the patient’s stool can be examined for the presence of tapeworm eggs or segments of the worm.

The definitive diagnosis is based on the detection of the eggs or proglottids in the feces, so a stool analysis is essential to confirm the presence of the parasite.

Blood tests: Elevated levels of vitamin B12 in the blood may indicate an infection with Diphyllobothrium.

Imaging studies: X-rays or a CT scan of the abdomen may reveal the presence of a tapeworm in the intestine.

Endoscopy: A thin tube with a camera on the end can be inserted into the intestine to directly visualize the tapeworm.

How To Avoid Diphyllobothrium latum Infection | Diphyllobothriasis Prevention

In addition to taking medication, it is important to practice good hygiene and sanitation to prevent reinfection.

Here are some preventive measures to help avoid Diphyllobothrium latum infection:

Cook fish thoroughly: Make sure to cook fish to an internal temperature of at least 145°F to kill any tapeworm larvae that may be present.

Avoid raw or undercooked fish: Especially from lakes, rivers, or other bodies of freshwater.

Wash hands thoroughly: Before eating and after handling raw fish or meat.

Practice good hygiene and sanitation: This includes washing hands frequently, keeping food preparation areas clean, and avoiding cross-contamination of raw and cooked foods.

Be cautious while traveling: Be careful while consuming raw or undercooked fish while traveling to areas where the infection is common.

Be selective: Be selective about the fish you eat, and avoid consuming fish that are known to be carriers of Diphyllobothrium latum, such as salmon and pike.

Seek medical attention: If you develop symptoms of tapeworm infection, such as abdominal pain, diarrhea, or malnutrition, seek medical attention immediately.

It’s important to note that these preventive measures are not guaranteed to protect you from infection, but they can significantly reduce the risk of infection.

Diphyllobothriasis Treatment

The treatment involves the use of one of the following medications:

Niclosamide: This medication is highly effective in killing the adult tapeworm and can be taken as a tablet or capsule.

Praziquantel: This medication is also highly effective in killing the adult tapeworm and can be taken as a tablet or capsule.

These medications are highly effective in killing the adult tapeworm, and can be taken as a tablet or capsule.

It’s important to note that these are prescription medications and should be taken under the supervision of a healthcare professional.

These medications are prescription drugs and are not recommended to be taken without a medical prescription.


  1. Durrani, M. I., Basit, H., & Blazar, E. (2022). Diphyllobothrium latum. In StatPearls [Internet]. StatPearls Publishing.
  2. Lacanaria, J. F. M., Miloren, B. G., Navarro, V. C. R., Piolo, A. I. Y., & Rosanes, J. A. A. (2020). Detection and identification of Diphyllobothrium latum (fish tapeworm) larvae in Eleutheronema tetradactylum (threadfin salmon) sashimi in selected food establishments in Imus City, Cavite.
  3. Greigert, V., Brunet, J., Pfaff, A. W., Lemoine, J. P., Candolfi, E., & Abou-Bacar, A. (2020). Locally acquired infection with Dibothriocephalus nihonkaiense (= Diphyllobothrium nihonkaiense) in France: the importance of molecular diagnosis. Parasitology research, 119(2), 513-518.
  4. Guo, A. J., Liu, K., Gong, W., Luo, X. N., Yan, H. B., Zhao, S. B., … & Jia, W. Z. (2012). Molecular identification of Diphyllobothrium latum and a brief review of diphyllobothriosis in China. Acta Parasitologica, 57(3), 293-296.
  5. Lee, K. W., Suhk, H. C., Pai, K. S., Shin, H. J., Jung, S. Y., Han, E. T., & Chai, J. Y. (2001). Diphyllobothrium latum infection after eating domestic salmon flesh. The Korean Journal of Parasitology, 39(4), 319.
  6. Nyberg, W. (1963). Diphyllobothrium latum and human nutrition, with particular reference to vitamin B12 deficiency. Proceedings of the Nutrition Society, 22(1), 8-14.
  7. Llaguno, M. M., Cortez-Escalante, J., Waikagul, J., Faleiros, A. C. G., Chagas, F. D., & Castro, C. (2008). Diphyllobothrium latum infection in a non-endemic country: case report. Revista da Sociedade Brasileira de Medicina Tropical, 41, 301-303.
  8. Wardle, R. A., & McColl, E. L. (1937). The taxonomy of Diphyllobothrium latum (Linne, 1758) in western Canada. Canadian Journal of Research, 15(9), 163-175.
  9. Nyberg, W., Gräsbeck, R., & Sippola, Ä. (1958). Urinary excretion of radiovitamin B12 in carriers of Diphyllobothrium latum. New England Journal of Medicine, 259(5), 216-219.
  10. Bonsdorff, B. V. (1956). Diphyllobothrium latum as a cause of pernicious anemia. Experimental Parasitology, 5(2), 207-230.
  11. McGAVRAN, E. G., & Songkla, M. (1928). Diphyllobothrium latum in Massachusetts: a report of two indigenous cases. Journal of the American Medical Association, 90(20), 1607-1608.
  12. Kim, J. H., & Lee, J. H. (2010). Diphyllobothrium latum during colonoscopy. New England Journal of Medicine, 362(11), e40.
  13. Lee, S. H., Park, H., & Yu, S. T. (2015). Diphyllobothrium latum infection in a child with recurrent abdominal pain. Korean journal of pediatrics, 58(11), 451.
  14. Guttowa, A., & Moskwa, B. (2005). The history of the exploration of the Diphyllobothrium latum life cycle. Wiadomosci Parazytologiczne, 51(4), 359-364.
  15. Iizuka, H., Kakizaki, S., & Onozato, Y. (2009). Diagnostic value of colonoscopy in intestinal Diphyllobothrium latum infection. Clinical Gastroenterology and Hepatology, 7(10), e62-e63.
  16. MAGATH, T. B. (1933). The relation of Diphyllobothrium latum infestation to the public health. Journal of the American Medical Association, 101(5), 337-341.
  17. Vergeer, T. (1928). Diphyllobothrium Latum (Linn., 1758), the Broad Tapeworm of Man: Experimental Studies. Journal of the American Medical Association, 90(9), 673-678.
  18. Van Doorn, H. R., Van Vugt, M., Wetsteyn, J. C., & Van Gool, T. (2005). Infestation with the tapeworm Diphyllobothrium latum after eating raw fish. Nederlands tijdschrift voor geneeskunde, 149(44), 2470-2472.
  19. Salminen, K. (1970). The effect of high and low temperature treatments on the infestiveness of Diphyllobothrium latum wih regard to public health. Acta Veterinaria Scandinavica, (Suppl. 32).
  20. Kuhlow, F. (1955). Researches on the Development of the Broad Tapeworm (Diphyllobothrium latum). Zeitschrift fur Tropenmedizin und Parasitologie, 6(2), 213-25.
  21. Mercado, R., Yamasaki, H., Kato, M., Muñoz, V., Sagua, H., Torres, P., & Castillo, D. (2010). Molecular identification of the Diphyllobothrium species causing diphyllobothriasis in Chilean patients. Parasitology research, 106(4), 995-1000.
  22. Fang, F. C., Billman, Z. P., Wallis, C. K., Abbott, A. N., Olson, J. C., Dhanireddy, S., & Murphy, S. C. (2015). Human Diphyllobothrium nihonkaiense infection in Washington state. Journal of Clinical Microbiology, 53(4), 1355-1357.
  23. Chen, S., Ai, L., Zhang, Y., Chen, J., Zhang, W., Li, Y., … & Yamasaki, H. (2014). Molecular detection of Diphyllobothrium nihonkaiense in humans, China. Emerging infectious diseases, 20(2), 315.
  24. Galán-Puchades MT. Human diphyllobothriasis. Lancet. 2020 Sep 12;396(10253):755. doi: 10.1016/S0140-6736(20)31192-2. PMID: 32919507.
  25. Zelia OP, Zavoikin VD, Plyushcheva GL. [(THE CURRENT SITUATION OF DIPHYLLOBOTHRIASIS: EPIDEMIOLOGY AND EPIDEMIOLOGICAL SURVEILLANCE)]. Med Parazitol (Mosk). 2017 Jan;1(1):52-59. Russian. PMID: 30721617.
  26. Kitaoka H, Takamizawa K, Shimizu N. Raw fish and diphyllobothriasis infection. QJM. 2020 Sep 1;113(9):695-696. doi: 10.1093/qjmed/hcaa008. PMID: 31926009.
  27. Dupouy-Camet J, Peduzzi R. Current situation of human diphyllobothriasis in Europe. Euro Surveill. 2004 May;9(5):31-5. PMID: 15208471.
  28. SHELIAPINA Ts. K voprosu o lechenii bol’nykh difillobotriozom [Treatment of diphyllobothriasis]. Sov Med. 1956 Aug;20(8):75-7. Russian. PMID: 13391153.
  29. Chernyshenko, A. I., Chistiakov, D. A., Shamarina, A. G., & Galeeva, L. N. (1979). Profilaktika difillobotrioza [Prevention of diphyllobothriasis]. Fel’dsher i akusherka44(1), 6–8.
  30. Goto, K., Hayashi, M., Inamori, M., Akiyama, T., Ikeda, T., Fujita, K., Ikeda, I., Fujisawa, T., Takahashi, H., Yoneda, M., Hara, K., Yasuzaki, H., Abe, Y., Kirikoshi, H., Kubota, K., Saito, S., Kawana, I., Ueno, N., Sakashita, T., & Nakajima, A. (2007). Education and imaging. Gastrointestinal: diphyllobothriasis. Journal of gastroenterology and hepatology22(3), 445. https://doi.org/10.1111/j.1440-1746.2007.04879.x