Elizabeth,
Thank you for representing our Veterans.  It is not a rumor that cholangiocarcinoma can be caused by parasites.   There are 2 parasites in particular which are classified by the World Health Orgnaizations as carcinogens for this type of cancer.  This cancer is relatively rare in the United States, but very prevalent in Asia, Vietnam, etc. 
My husband was a Vietnam Veteran and passed away from this cancer.  I have a lot of information.  If any Vietnam Veteran or someone who is working with a Vet that needs the information, I will be happy to share all my research and a copy of the claim that I sent.  Since I was checking mainly about Vietnam, I didn't go into detail about other places in Asia.  However, I know it is very prevalent in Thailand, also.  I can be reached through my email,
petitti.mario@yahoo.com
I will be happy to help anyone regarding this if they are making a claim. I have statistics where it shows the amount of people in the U.S. getting this cancer compared to the number of Vietnam immigrants and the difference is astronomical.
These parasites live in the muscle of the fish and if the fish is not frozen correctly they may still be there, then if it is not cooked correctly, it may be there.  A person may or may not have symptoms when they eat the fish that has the parasites.   The parasites may be excreted or even killed off, but they already have done damage to the DNA of the bile duct and it usually takes between 30-to 40 years for the cancer to develop.  That is why many of our vets are coming down with it now.   Also, many times it is misdiagnosed because it ends up in the liver, so it is just stated as a liver cancer.  Won't go into any more detail here, but just wanted to let you know to contact me if I can be of help.  As stated in a previous reply, Sheila Harrison is a great source of information.  She was the one who put the whole thing together when her husband passed away from this cancer.  Just a note to all others, I am not a sushi eater, nor was my husband, although he did have some smoked fish in Vietnam.  I don't want to start rumors either and I don't know if this is true, but if you notice most of our fish is now coming from Vietnam or Thailand.  Don't want to alarm anyone, but I would be very careful about eating fish from there and would never ever eat sushi from anywhere.