Okay, I'm going against DH's post up there.
We used Duramycin-10 for both chickens AND ducks. Thank god we only had ONE duck get sick. I brought her inside and kept her inside away from the others. I used Duramycin-10 and the vitamin/electrolyte packets. I only put a small amount of both in her water (I let her use the quart sized water container), and she only got it 3 times a day.
She did go off her feed for a while, but she did get better and everything worked out fine.