“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.