Overview of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 33

2.4.2. Fasciola
There are two species, Fasciola hepatica and Fasciola gigantis , implicated in
waterborne human disease. These trematode worms, also known as liver
flukes, infect an estimated 2.4-17 million people globally. There is also a
water host, namely the snail. The snail releases infectious metacercariae that,
when ingested, excyst in the human stomach and migrate to the liver and
bile ducts. The acute phase, associated with the maturation of these excysted
flukes, results in symptoms such as dyspepsia, nausea and vomiting, abdomi-
nal pain and high fever. Subsequently, the mature adult flukes release eggs
that are excreted back into the water environment, and they can live inside
the host for 9-14 years ( Fig. 2.11 ). The metacercariae exhibit a high resis-
tance to disinfection by chlorine, but they can be removed by filtration. In
most regions, fasciolasis is spread through eating wet grass or aquatic plants,
such as watercress, although drinking water may be a significant transmis-
sion route for fasciolasis in certain locations, e.g. the Andean Altiplano
region in South America.
Figure 2.11 Life cycle of fasciola . Source: http://www.dpd.cdc.gov/dpdx/HTML/
Fascioliasis.htm. (For color version of this figure, the reader is referred to the online
version of this topic.)