The Department of Veterans Affairs this spring commissioned a small pilot study to look into the link between liver flukes ingested through raw or undercooked fish and a rare bile duct cancer. It can take decades for symptoms to appear. By then, patients are often in tremendous pain, with just a few months to live.

Of the 50 blood samples submitted, more than 20 percent came back positive or bordering positive for liver fluke antibodies, said Sung-Tae Hong, the tropical medicine specialist who carried out the tests at Seoul National University in South Korea.

“It was surprising,” he said, stressing the preliminary results could include false positives and that the research is ongoing.