X2.. I believe I saw on here it's around 20.00 to do a fecal, then you'd know what you need to do to help this duck.If you could find a Vet who will test a stool sample for you would be the best thing at this point. I don't believe the fees are the same as an office visit. Or find your State Vet's office and get it done through them. Somethings not quite right and you really do need to get this checked out somehow. Ducks, because of their higher body temperature, aren't normally prone to worms or other internal parasites. Filthy conditions can bring them on or adding new birds who may have been in less than desirable conditions can also bring them in. If you aren't having any of these things going on, you will need to look further and a Vet is able to do the right tests. We can only guess.