Schistosomiasis and Other Trematode Infections


Trematodes, including schistosomes, are parasitic flatworms (flukes) infecting both humans and animals. Various freshwater snails are intermediate hosts. Human water contact is a key element in schistosomiasis transmission. Infection takes place when cercariae penetrate intact skin exposed to infested water. For all other trematodes, humans become infected by ingestion of metacercariae in crustacea, fish or plants, the second intermediate host, hence the term foodborne trematodes. Most of the trematodes are zoonotic and infect a wide range of domestic and wild animals as well as man. Based on the location of the adult worms, flukes can be grouped as blood (schistosomes), liver, lung or intestinal flukes. Infections can lead to serious diseases and are of economic importance owing to the high number of infections worldwide. Control strategies should include treatment of affected populations to reduce the burden of disease, health education and effective control of animal reservoir hosts.

Key concepts:

  • Schistosmiasis affects the general health and well being of millions of people.

  • Integration of schistosomiasis control measures into existing public health services are vital for longā€term success.

  • Agricultural development projects and irrigation can increase the risk of schistosomiasis transmission.

  • Domestic animals play an important role in the transmission of liver and intestinal trematodes.

  • Control of foodborne zoonotic trematodes requires effective control of the reservoir hosts.

  • Health education is an essential element in control of foodborne zoonotic trematodes.

Keywords: schistosomiasis; liver flukes; foodborne trematodes; zoonoses; praziquantel

Figure 1.

The basic lifecycles of the principal schistosomes infecting man.

Figure 2.

Life cycle of Opisthorchiidae. Stages in the snail host from the left: miracidium; sporocyst; redia; cercaria. Courtesy of Chongkham Phonekeo, WHO, Lao PDR



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Vennervald, Birgitte J, and Johansen, Maria V(Dec 2009) Schistosomiasis and Other Trematode Infections. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0002249.pub2]