Definition of Hymenolepiasis:

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 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.