Sick cat (update).

Our cat (Ella) is slowly improving. Her fever has dropped to high-normal, she's alert and responsive, and her appetite is back. But she's still very uncomfortable and staying in bed most of the day.

The current guess is that it probably is a result of her vaccinations. The timeline and symptom set matches something called "post-calicivirus vaccine transient polyarthritis". And pretty much every other possibility has been ruled out.  

Since she's eating and drinking and her fever is better we're waiting to see what happens over the weekend. The post vaccine syndrome goes away on its own, and only requires pain management and supportive care if need be.

If she stops getting better or gets worse again, we see a specialty vet early next week for further evaluation. It could be an ongoing immune mediated polyarthritis issue which would require some more advanced diagnostics to confirm and set up a treatment plan.

But given all the things that the previous lab tests and examinations ruled out, it is almost certainly one or the other. And as of now there's no serious danger.

So, hoping for the best.