Background: Travel and global military presence dictate that international diseases can affect the American populace. Eastern Asia is experiencing an endemic of liver fluke worm disease, with 30% to 75% of the population being infected due to eating raw fish, and an estimated 35 million people infected throughout the world.1-3 The 2 flukes concerning healthcare providers are Opisthorchis viverrini and Clonorchis sinensis because they have been linked to bile duct cancer.1-5 Fluke worm disease is preceded by inflammation in the bile duct that causes scarring in the tissue and increases the risk for a bile duct cancer called cholangiocarcinoma.1-5 By the time the host is diagnosed, the cancer is typically widespread and mortality increases quickly regardless of treatment. Fluke worm has been known to lie dormant for years without side effects, making detection a challenge.
Objectives: Navigators should bring awareness to the increased risk of the development of this cancer among those who work in or travel to these areas.
Methods: Advanced Internet search was performed, and the cost of Ova and Parasite (O&P) testing was investigated.
Results: The average prevalence rate of opisthorchiasis in northern Thailand is 22%. In Khon Kaen, the prevalence rate of O. viverrini infection is 94%, and the infection is endemic in Thailand, Laos, Vietnam, and Cambodia. The cholangiocarcinoma rate is 0.2 to 0.7 per 100,000 people in Western countries, with incidence in Japan and Singapore at 1.0 per 100,000 people, 7.4 in Korea, and 84.6 in northern Thailand.2
One small study of immigrants tested for O&P after arriving in the United States revealed 17 positive cases out of 1800 stool samples tested. Some participants were diagnosed with liver fluke infestations within 3 months of arrival and some after years. One study revealed that more than 20% of 50 blood samples from the Vietnam veterans at the Northport VA Medical Center in New York were positive or near-positive for worm-specific antibodies.3,4 No studies were found with broad screening for O&P of US veterans with a history of traveling abroad.
In Thailand alone, there is an estimated cost of US $120 million annually in medical care and lost wages. Cost of O&P testing varies by laboratory in the United States, with a single test kit ranging from $60 to $201 when 7 labs were surveyed. Blood testing costs were unobtainable for antibodies.
Conclusion: The fluke worm, a known causative agent for cholangiocarcinoma, is transmitted by ingestion of undercooked fish, especially in Eastern Asia. American government workers, relocating populations, and travelers to the area may become infected and increase the risk of developing this cancer.
O&P screening tests are inexpensive and noninvasive and can detect the fluke worm. Navigators should advocate for early, inexpensive screening for the fluke worm to decrease the prevalence or severity of cholangiocarcinoma. Fluke worm testing should be considered in high-risk populations on a regimen similar to colon screening, every 5 to 10 years after exposure, due to the risk of dormancy.
- American Cancer Society Medical and Editorial Content team. Parasites that can lead to cancer. www.cancer.org/cancer/cancer-causes/infectious-agents/infections-that-can-lead-to-cancer/parasites.html. Updated July 11, 2016.
- Lim JH. Liver flukes: the malady neglected. Korean Journal of Radiology. 2011;12(3):269-279.
- Abassi L. Undetected Parasitic Infection May Cause Deadly Cancer in Vietnam Vets. American Council on Science and Health. www.acsh.org/news/2017/11/24/undetected-parasitic-infection-may-cause-deadly-cancer-vietnam-vets-12187. November 24, 2017.
- US Department of Veterans Affairs. Public Health. Bile Duct Cancer (Cholangiocarcinoma) and Liver Fluke Infection. www.publichealth.va.gov/exposures/infectiousdiseases/cholangiocarcinoma.asp. Updated March 6, 2018.
- Harkins G. VA studies Vietnam vets for exposure to cancer-causing parasite. www.moaa.org/Content/Publications-and-Media/News-Articles/2017-News-Articles/Vietnam-vets-parasite-cancer-fish-liver-flukes-bile-duct-cholangiocarcinoma.aspx. November 30, 2017.