Dwarf tapeworm infection

Alternative names
Hymenolepiasis; Rat tapeworm; Tapeworm - infection

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

Causes, incidence, and risk factors

Hymenolepis live in warm climates and are common in the southern U.S. The eggs of these worms are ingested by insects, and mature into a life form referred to as a “cysticercoid” in the insect.

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 U.S., 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:

  • gastrointestinal discomfort  
  • diarrhea  
  • weakness  
  • poor appetite

Signs and tests
Examination of the stool for eggs and parasites confirms the diagnosis


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

Expectations (prognosis)
Expect full recovery following treatment.


  • abdominal discomfort  
  • dehydration from prolonged diarrhea

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

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

Johns Hopkins patient information

Last revised: December 4, 2012
by Janet G. Derge, M.D.

Medical Encyclopedia

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0-9

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.