Oh I'm so sorry to hear this! I found that niacin worked quickly for us but it is also a long road. The problems improved but didnt completely go away even after weeks of treatment. That appears to be a long road. I think
@issac 0 warned about that....
On the other hand, any time one of my animals was improving and takes such a sudden turn for the worse, which includes not wanting to drink (I feel that drinking is critical, more so than food, and especially for ducks), I start considering a trip to the vet. In your case, because there was this period before the niacin treatment where she seemed a bit off and I suppose we can't rule out that it might not have been two things that were bothering her, I'm rather concerned. Here are some ideas I'm going to throw out there even though I'm not a duck expert (though I do have ducks for the past few months).
Does your local vet see birds?
Can you tell if she has a high temperature (sign of fighting off some kind of infection)?
In my experience, if it isn't an injury, it can be a parasite or other infection that suddenly got very bad or was developing unnoticed. A vet could also look for parasites in the poop even if there is no fever. Even if a vet doesn't see ducks, most vets can check for cocci or worms because other animals they treat can be affected by them. That being said, one of my vets missed a massive cocci infection, and luckily we drove the hour to an avian vet who squeezed us in for a second opinion. Anyway, I know that isn't often available, but if it is, I would consider getting her checked for parasites.
For various reasons including risk of dehydration, blockage in the nostrils, and considering if there is some kind of blockage somewhere in the digestive tract, I feel it is important to monitor the drinking and pooping critically; does your duck also refuse water?? If she is drinking, how much? When did she last poop? What was the poop like?
Because she doesnt want to eat, this might not be the case, and I'm aware that there is no true crop in a duck. Nonetheless, it is still worth asking, considering that she might have ingested something dubious: is the crop area or throat swollen? Is she burping any weird smells? Whenever I've dealt with impacted crop, my chickens were actually very hungry as no nutrition was getting into their guts.
Is it possible that your duck ingested something that got through the crop area but is wreaking havoc elsewhere, like string?
I really hope that someone else has better/more ideas. I hate these moments and will cross my fingers for the best! Please post with an update when you can!
