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Dwarf tapeworm infection; Rat tapeworm; Tapeworm - infection

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

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  • Causes

    Hymenolepis 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 intentionally or unintentionally 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

    Examination of the stool for eggs confirms the diagnosis.

  • Treatment

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

  • Outlook (Prognosis)

    Expect full recovery following treatment.

  • Possible Complications

    • Abdominal discomfort
    • Dehydration from prolonged diarrhea
  • When to Contact a Medical Professional

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

  • Prevention

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

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Blanton R. Adult tapeworm infections. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th Ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 294.

Richardz FO Jr. Diphyllobothrium, Dipylidium, and Hymenolepsis species. In: Long SS, ed. Principles and Practice of Pediatric Infectious Diseases. 3rd ed. Philadelphia, PA: Churchill Livingstone Elsevier; 2008:chap: 279.


Review Date: 9/1/2013  

Reviewed By: 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, Bethanne Black, and the A.D.A.M. Editorial team.

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