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[Bolbosoma spp.] [Macracanthorhynchus hirudinaceous] [Moniliformis moniliformis]
The principle agents of acanthocephaliasis in humans are the thorny-headed worms, Macracanthorhynchus hirudinaceous and Moniliformis moniliformis. Bolbosoma species have also been known to infect humans.
Eggs are shed in the feces of the definitive hosts , 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 , 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 molts into a second larval stage, called an acanthella . After 6-12 weeks, the worm reaches the infective stage called a cystacanth . 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 mature and mate in about 8-12 weeks. In humans the worms seldom mature, or mature but will rarely produce eggs.
Acanthocephalans are widely distributed and cases of acanthocephaliasis generally occur in areas where insects are eaten for dietary or medicinal purposes.
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.