upper respiratory infection

Hi all,

We had two fancy mice, Squeakers and Coco. Squeakers appeared to have
an upper respiratory infection. She was panting, lethargic, etc. I
took her to a vet, who supposedly treats rodents, but upon examining
her, I think he accidentally broke her spine, and she died while we
were there. My son is extremely heart-broken.

Anyway, Coco now seems to be sneezing periodically. I am not taking
her to the vet, since the first time was a fiasco. I did a web search
and found the respiratory infections are common and to treat with
tetracycline. I found some that is meant to be dissolved in drinking
water for birds, and I have put that into Coco's drinking water.

My question is, has anyone had success with treating the infection? We
want to get another mouse, because Coco is lonely now that her best
friend is gone, but I don't want to get one until she seems well.

Any suggestions?
Misty