I did worm him - it didn't help, just made him sick for a few days. I also gave him brewer's yeast in his food for months, and probiotic supplements. I guess it was just a very slowly progressing virus, or some kind of neurological defect. He had a fantastic appetite right up until the end...I just couldn't watch him do nothing but sit in a box any longer, so I put him to sleep. That's no kind of life for a duck - unable to walk, fly, and barely even swim.I'm so sorry guys. For the future when in doubt worm them and try apple cider vinegar it works wonders. Doing this will also mean any supplements you give are given the best chance. Again so sorry.