It has been studied and found to have no effect on humans. If you cook the breasts properly (which I do, I like 'em doused in a marinade I make, and crispy) the parasites die quickly.
I did it just to say I did it, but I probably won't eat any more ducks I shoot that have that condition. It's fairly rare to find one anyhow. That one I shot last year was my first with Rice Breast.