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DPDx

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Acanthocephaliasis

[Bolbosoma spp.] [Macracanthorhynchus hirudinaceous] [Moniliformis moniliformis]

Egg of M. hirudinaceous in an unstained wet mount of stool.

Egg of M. hirudinaceous in an unstained wet mount of stool.


Egg of M. moniliformis liberated from an adult worm that was recovered from the stool of a patient.

Egg of M. moniliformis liberated from an adult worm that was recovered from the stool of a patient.


Adult of M. hirudinaceous.

Adult of M. hirudinaceous.

Causal Agents

The principle agents of acanthocephaliasis in humans are the thorny-headed worms, Macracanthorhynchus hirudinaceous and Moniliformis moniliformisBolbosoma species have also been known to infect humans.


Life Cycle

Life cycle of acanthocephalans

Eggs are shed in the feces of the definitive hosts The number 1, which are usually rats for M. moniliformis and swine for M. hirudinaceous, although carnivores and primates, including humans, may serve as accidental hosts. The eggs contain a fully-developed acanthor when shed in feces. The eggs are ingested by an intermediate host The number 2, which is an insect (usually scarabaeoid or hydrophilid beetles for M. hirudinaceous and beetles or cockroaches for M. moniliformis). Within the hemocoelom of the insect, the acanthor The number 2a molts into a second larval stage, called an acanthella The number 2b. After 6-12 weeks, the worm reaches the infective stage called a cystacanth The number 2c. The definitive host becomes infected upon ingestion of intermediate hosts containing infective cystacanths . In the definitive host, liberated juveniles attach to the wall of the small intestine, where they matureThe number 4 and mate in about 8-12 weeks. In humans The number 2a the worms seldom mature, or mature but will rarely produce eggs.

Geographic Distribution

Acanthocephalans are widely distributed and cases of acanthocephaliasis generally occur in areas where insects are eaten for dietary or medicinal purposes.

Clinical Presentation

Clinical symptoms of acanthocephaliasis are often severe, due in part to the mechanical damage caused by the insertion of the armed proboscis into the lumen of the host's intestine. Symptoms may include abdominal pain and distension, fever, decreased appetite, nausea, vomiting, weight loss, diarrhea, constipation or bloody stools.

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  • Page last reviewed November 29, 2013
  • Page last updated November 29, 2013
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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