“Toxic Hitchhikers”
in the March/April 2014 issue reported on parasites from war zones and
the illnesses they have caused. One of the most insidious is the liver
fluke—Opisthorchis viverrini or Clonorchis sinensis—a freshwater-fish-borne flatworm that causes cholangiocarcinoma (cancer of the bile duct).
Cholangiocarcinoma
is widespread in areas of Southeast Asia due to the popularity of
traditional dishes in which fish is either raw or insufficiently cooked
to kill the parasite. Many veterans who served in or near Vietnam
acquired the parasite.
What
makes liver fluke infection especially ominous is that the parasite can
live and reproduce in the bile duct for thirty years or longer. This
causes chronic inflammation that eventually creates cancerous cells
before producing noticeable symptoms. Although detection and elimination
of the parasite are easy at an early stage, all too often the infection
is not discovered until a patient has Stage IV cancer. Typically, the
first visible signs include jaundice resulting from a blocked bile duct.
At this stage, the prognosis is dismal, and the same cancerous blockage
that causes jaundice also locks in a still-thriving colony of liver
flukes, preventing their detection in stool samples.
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