It's called sarcocystocis or in ducks "rice breast disease". It's caused by a protozoan parasite. They are destroyed by cooking and you don't see them in cooked ducks. All the same, if I see them, I normally don't eat them. see
http://www.unbc.ca/nlui/wildlife_dis...arcocystis.htm I attempt to remove all the spaghetti worms from trout and reds that I see. There's just something about eating parasites.