Doctors battle cancer-causing Thai fish dish

It wasn't until he got to medical school that Narong Khuntikeo finally discovered what caused the liver cancer that took both of his parents' lives: their lunch.

Like millions of Thais across the rural northeast, his family regularly ate koi pla - a local dish made of raw fish ground with spices and lime.

The pungent meal is quick, cheap and tasty, but the fish is also a favorite feast for parasites that can cause a lethal liver cancer killing up to 20,000 Thais annually.