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Cyclophyllidian gut tapeworms 

Cyclophyllidian gut tapeworms

Chapter:
Cyclophyllidian gut tapeworms
Author(s):

Richard Knight

DOI:
10.1093/med/9780199204854.003.071002_update_001

Update:

Epidemiology—Geographic distribution updated; Taenia asiatica now known to be quite widespread in east Asia and South-East Asia.

Phylogeny—human taeniasis predates domestication of cattle and pigs.

Updated on 31 May 2012. The previous version of this content can be found here.
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date: 25 March 2017

The cyclophyllidean tapeworms are cestodes that maintain anchorage to the host small-gut mucosa by means of a scolex bearing four suckers; mature reproductive proglottids develop at the end of the worm. The life cycle involves a cystic larval stage, usually in a nonhuman host species. Humans are an obligatory part of the life cycle in four gut species; in the rest they are an accidental host.

Taenia saginata

The beef tapeworm is common in Africa, the Middle East, Asia and South America. It remains endemic, although now rare, in the United States of America and western Europe. Transmission occurs where cattle have access to human faeces and where humans eat undercooked beef containing cysts. Many people who are infected have no symptoms, except that they experience active exit of single proglottids through the anus. Diagnosis is by finding typical eggs in perianal swabs. Treatment is with niclosamide or praziquantel. Prevention is by health education concerning production and cooking of meat, also by proper sewage treatment and disposal. Mass treatment of selected or whole adult populations is the most effective short-term measure when endemicity is high.

Taenia asiatica

Adult worms resemble T. saginata but the cysts are much smaller and occur in the liver of pigs and wild boar. First recognized in 1973 and now known to be quite widespread in east Asia and South-East Asia. Cattle are not involved in the life cycle.

Taenia solium

Adult pork tapeworm infections occur when cysts in undercooked pig meat are eaten. High prevalences occur in Africa, parts of Asia, and Central and South America. Symptoms, diagnosis and treatment are similar to those of T.saginata. The potentially dangerous condition of cysticercosis occurs when eggs from the faeces of persons harbouring adult worms are ingested; this produces cysts in striated muscle, subcutaneous tissue, nervous system and the eye. See Chapter 7.10.3 for further discussion.

Other tapeworms

Several species are recognized as accidental human parasites, but Hymenolepis nana, the dwarf tapeworm, is common; the life cycle involves only humans. Heavy infection can lead to anorexia, abdominal pain, and malabsorption. Diagnosis is by finding eggs in the faeces. Treatment is with praziquantel or niclosamide.

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