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Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or Hymenolepis diminuta.

Alternative Names

Dwarf tapeworm infection; Rat tapeworm; Tapeworm - infection


Hymenolepis live in warm climates and are common in the southern United States. The eggs of these worms are ingested by insects.

Humans and other animals become infected when they intentionally or unintentionally eat material contaminated by insects. In an infected person, it is possible for the worm's entire life-cycle to be completed in the bowel, so infection can persist for years.

Hymenolepis nana infections are much more common than Hymenolepis diminuta infections in humans. These infections were previously common in the southeastern United States, and have been described in crowded environments and individuals confined to institutions. However, the disease occurs throughout the world.


Symptoms occur only with heavy infections. Symptoms include:

  • Diarrhea
  • Gastrointestinal discomfort
  • Itchy anus
  • Poor appetite
  • Weakness
Signs and tests

Examination of the stool for eggs confirms the diagnosis.

Support Groups

Expectations (prognosis)

Expect full recovery following treatment.

Calling your health care provider

Call your health care provider if chronic diarrhea or abdominal cramping are present.

  • Abdominal discomfort
  • Dehydration from prolonged diarrhea

Praziquantel as a single dose is the current treatment of choice for this condition.


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


Blanton R. Adult tapeworm infections. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th Ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 299.

Richard FO Jr. Diphyllobothrium, dipylidium, and hymenolepsis species. In: Long SS, Pickering LK, Prober CG. Principles and Practice of Pediatric Infectious Diseases. 3rd ed. Philadelphia, Pa: Churchill Livingstone Elsevier; 2008: chap: 279.

Review Date: 8/28/2009
Reviewed By: Linda Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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