Very Sick Duck - Coccidiosis

One of my ducks came out of the coop Tuesday morning unable to walk.  Took her to the vet and she was diagnosed with coccidiosis.  Began treatment on her, all the other ducks, and all our chickens (which are housed separately).  She was standing a bit, off and on last couple of days, and eating a bit.  This morning she is not doing well at all.  She can't stand at all or even sit up straight.  

i've read that coccidiosis damages the intestinal walls, limiting the bird's ability to assimilate food, and that the damage is permanent.  i'm feeling like this little duck might not make it.  Will start force feeding momentarily.  But i am also wondering if it would be the kindest thing to have her euthanized.  If anyone has any experience with cocci in ducks, i really need some input.  Thanks.

Thank you so much Miss Lydia and Rubber Duckee for your replies.  It has been such a struggle getting answers to the many questions i have about this disease.  i spoke with a vet at the animal health poultry lab in Turlock, although they tend to primarily deal with large scale operations. He said there are many varieties of coccidiosis and that they are species specific.  So the strain that is effecting our chickens and ducks would not be the kind our cats or we could catch.  Our vet's office didn't specify what strain we have here, and i would really like to know.  Wondering where we could get a soil sample tested.

Our little duck, Portia de Rossi, is hanging in there, though not improving.  i hate to take a life if there is any chance of recovery.  She is still lively enough to bite me when i try to give her the medication.  RubberDuckee, your comment made me think that perhaps giving her subque fluids would help.  i did take her in on the first day for fluids, and that seemed to help.

Oh, this poultry specialist also indicated that they recommend not treating until an animal shows symptoms, or the cocci levels are high in the fecal sample.  He said that a healthy bird should develop immunity to it after exposure.  i guess my next question would be, after i treat all my birds, does that ensure they won't contract this particular strain again?  And then, after over 4 years here, why are they just now contracting it.  Where did it come from?  Maybe wild birds?

Well, i never expected all these roller coasters when i first got into chicken, duck, and geese ownership.  It's not for the faint of heart.  Thanks again for your input.  It really helps to have someone to talk to about this.

Good news - Portia was standing up yesterday, and biting harder.  So i feel like we've turned a corner.  She is also eating a bit on her own.  Although i am force feeding her watered-down baby parrot formula.  Her poos are still pretty watery. Today is the last day of the medication.  i wonder if i should go one more day.  As unpleasant as it is to have a duck in the house, i would like to keep her in and bulk her back up with vitamins, probiotics, and good food before letting her back out.  Plus, we are in triple digits here, all last week and predicted to go through to the end of the week.  i don't want her heat-stressed at this critical juncture.  Hoping she continues to recover.