Overview
Diphyllobothriasis is an infection caused by large tapeworms belonging to the Diphyllobothrium family, most commonly Diphyllobothrium latum, sometimes called the 'fish tapeworm' or 'broad tapeworm.' People get this infection by eating raw or undercooked freshwater fish that carry the parasite's larvae. Once swallowed, the tapeworm attaches to the lining of the small intestine and can grow to enormous lengths — sometimes over 10 meters (about 30 feet) — while living inside the body for years or even decades. Many people with diphyllobothriasis have no symptoms at all and only discover the infection when they notice worm segments in their stool. When symptoms do occur, they usually involve the digestive system: stomach pain, nausea, diarrhea, or a feeling of fullness. One important complication is vitamin B12 deficiency, because the tapeworm competes with the body for this essential nutrient. Severe B12 deficiency can lead to anemia and nerve problems if left untreated. The good news is that treatment is straightforward and highly effective. A single dose of the antiparasitic medication praziquantel (or sometimes niclosamide) typically eliminates the tapeworm completely. With prompt treatment, most people recover fully with no lasting health effects. Prevention focuses on thoroughly cooking freshwater fish or freezing it at very low temperatures before eating.
Also known as:
Key symptoms:
No symptoms at all (many people are unaware they are infected)Stomach pain or crampingNauseaDiarrhea or loose stoolsConstipationFeeling unusually full or bloatedUnexplained weight lossFatigue and low energySeeing worm segments or a long worm in the stoolVitamin B12 deficiency leading to anemiaTingling or numbness in hands and feet (from B12 deficiency)Dizziness or lightheadedness
Sporadic
Usually appears on its own, not inherited from a parent
Variable
Can begin at different ages, from infancy through adulthood
Treatments
No FDA-approved treatments are currently listed for Diphyllobothriasis.
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Specialists
View all specialists →No specialists are currently listed for Diphyllobothriasis.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Diphyllobothriasis.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.How do I take the medication correctly, and are there any side effects I should watch for?,Do I need a follow-up stool test to make sure the tapeworm is gone?,Should I be tested for vitamin B12 deficiency, and do I need supplements?,Could other members of my family or household also be infected?,How long might I have had this infection, and could it have caused any lasting damage?,What foods or food preparation methods should I avoid to prevent getting this infection again?,When can I expect to feel completely back to normal after treatment?
Common questions about Diphyllobothriasis
What is Diphyllobothriasis?
Diphyllobothriasis is an infection caused by large tapeworms belonging to the Diphyllobothrium family, most commonly Diphyllobothrium latum, sometimes called the 'fish tapeworm' or 'broad tapeworm.' People get this infection by eating raw or undercooked freshwater fish that carry the parasite's larvae. Once swallowed, the tapeworm attaches to the lining of the small intestine and can grow to enormous lengths — sometimes over 10 meters (about 30 feet) — while living inside the body for years or even decades. Many people with diphyllobothriasis have no symptoms at all and only discover the infe
How is Diphyllobothriasis inherited?
Diphyllobothriasis follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.