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Tapeworm infection - hymenolepis

Hymenolepiasis; Dwarf tapeworm infection; Rat tapeworm; Tapeworm - infection

A hymenolepis infection is an infestation by one of two species of tapeworm: Hymenolepis nana or Hymenolepis diminuta. The disease is also called hymenolepiasis.

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Causes

Hymenolepis worms live in warm climates and are common in the southern United States. Insects eat the eggs of these worms.

Humans and other animals become infected when they eat material contaminated by insects (including fleas associated with rats). In an infected person, it is possible for the worm's entire life cycle to be completed in the bowel, so infection can last for years.

Hymenolepis nana infections are much more common than Hymenolepis diminuta infections in humans. These infections used to be common in the southeastern United States, in crowded environments, and in people who were confined to institutions. However, the disease occurs throughout the world.

Symptoms

Symptoms occur only with heavy infections. Symptoms include:

• Diarrhea
• Gastrointestinal discomfort
• Itchy anus
• Poor appetite
• Weakness

Exams and Tests

A stool exam for the tapeworm and its eggs confirms the diagnosis.

Treatment

The treatment for this condition is a single dose of praziquantel, repeated in 10 days.

Household members may also need to be screened and treated because the infection can be spread easily from person to person.

Outlook (Prognosis)

Expect full recovery following treatment.

Possible Complications

Health problems that may result from this infection include:

• Abdominal discomfort
• Dehydration from prolonged diarrhea

When to Contact a Medical Professional

Contact your health care provider if you have chronic diarrhea or abdominal cramping.

Prevention

Good hygiene, public health and sanitation programs, and elimination of rats help prevent the spread of hymenolepiasis.

Related Information

References

Fairley JK, O’Connell EM. Tapeworms (cestodes). In: Blaser MJ, Cohen JI, Holland SM, et al, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 10th ed. Philadelphia, PA: Elsevier; 2026:chap 295.

Fischer PR, White AC. Adult tapeworm infections. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 348.

White AC, Brunetti E. Cestodes. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 325.

Review Date: 8/5/2025  

Reviewed By: Jatin M. Vyas, MD, PhD, Roy and Diana Vagelos Professor in Medicine, Columbia University Vagelos College of Physicians and Surgeons, Division of Infectious Diseases, Department of Medicine, New York, NY. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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