Hundreds of millions of people, particularly those who live in
rural areas or deprived urban settings in the developing world,
are at risk of acquiring foodborne trematodiasis and schistosomiasis.1-3
Foodborne trematodiasis include clonorchiasis, paragonimiasis,
fascioliasis, and opisthorchiasis. These and schistosomiasis all
belong to the subclass of Digenea, class of Trematoda, phylum of Platyhelminthes.
The taxonomy of Platyhelminthes is shown in eFigure 335.1. Digeneans,
also known as flatworms, are characterized by dorsoventral flattening,
presence of an oral sucker and often a ventral sucker, and lack of
a circulatory system.4Figure
335-1 shows, by means of scanning electron microscopy, the
head portion of an adult Clonorchis sinensis (a
liver fluke), clearly depicting some of the typical features of
Taxonomy of Platyhelminthes.
Scanning electron microscopic image of the head portion
of an adult Clonorchis sinensis fluke (OS, oral
sucker; VS, ventral sucker).
The endemic regions of the world, global burden and at risk populations
for infection with clonorchiasis, fascioliasis, fasciolopsiasis, opisthorchiasis,
paragonimiasis, and schistosomiasis are summarized in Table
Table 335-1. Schistosomiasis
and Foodborne Trematodiasis |Favorite Table|Download (.pdf)
Table 335-1. Schistosomiasis
and Foodborne Trematodiasis
|Disease||Causative Agent(s)||Endemic Areas||At-risk Population (in millions)||Number of People Infected (in millions)||Age and Sex-Related Infection Patterns|
|Schistosomiasis||Schistosoma haematobium||Sub-Saharan Africa, Middle East, some islands in the Indian
Ocean||779||207||School-age children are usually at highest
risk of infection. Occupation (eg, fishermen) is a risk factor of
|S mansoni||Sub-Saharan Africa, parts of South America (eg, Brazil),
some Caribbean islands|
|S japonicum||China, Indonesia, the Philippines|
|S intercalatum||Parts of Central and West Africa|
|S mekongi||Cambodia, Lao PDR|
|Clonorchiasis||Clonorchis sinensis||China, Republic of Korea, Taiwan, Vietnam||601||35||No uniform age distribution. Often infection rates increase
with age and higher prevalence observed in males|
|Opisthorchiasis||Opisthorchis felineus||Siberia, Kazakhstan, Russian Federation, Ukraine||12.5||1.2||Not known|
|O viverrini||(Cambodia), Lao People’s Democratic Republic, Thailand,
Vietnam||67||9||Low prevalence in young children. Highest prevalence and
intensities observed in young adults and adults|
|Fascioliasis||Fasciola hepatica, F gigantica||Bolivia, Ecuador, Peru, Chile, Egypt, Islamic Republic of
Iran, Cuba, Portugal, France, Spain||91||2.4-17||School-age children mostly affected; higher prevalence and
intensities among females|
|Paragonimiasis||Paragonimus species||Cameroon, China, Costa Rica, Ecuador, Equatorial Guinea,
Gabon, Guatemala, India, Japan, Lao People’s Democratic Republic,
Liberia, Malaysia, Mexico, Nepal, Pakistan, Panama, Nigeria, Peru, Philippines,
Republic of Korea, Siberia, Sri Lanka, Taiwan, Thailand, Vietnam||293||> 20||School-age children and young adults mostly affected|
|Fasciolopsis buski||Bangladesh, China, India, Indonesia, Malaysia, Taiwan, Thailand,
Vietnam, Lao People’s Democratic Republic, Indonesia, Cambodia,
Philippines ||?||?||School-age children ...|
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