Mice with a possible URI?

Question
QUESTION: I have two female mice. I've had them for a couple of months now with no issues. However, over the past week, they both have started sneezing or squeaking occasionally. It's not constant, and they have no other symptoms of illness. They are both very active throughout the day and night and are eating and drinking regularly.

Money is tight at the moment because of the holidays, so I'm hoping a vet visit isn't needed (though if it becomes necessary, I have already found a vet who can treat them).
I have been administering tetracycline to them via their water bottle, after following the instructions that I read on this site (and I have tinfoil over the bottle to keep light out). However, after about five days, they are continuing to occasionally sneeze. Still with no other symptoms.
I clean their cage regularly, I use only unscented dish soap, and they have Carefresh Natural bedding. Their bedding, food, and toys have consistently been the same type and brand, so I don't believe this could be an allergy.

How long does tetracycline generally take to clear up the illness?

Or, is it possible that they are simply reacting to the cold/dry air in my room, and are not actually sick? The air has been significantly drier lately as the temperatures in my area have dropped.

I've been extremely worried about them, and I'm hoping that the sneezing will clear up before it becomes something serious. These are the first mice I've ever had, so I don't have much experience, but I want to keep them as happy and as healthy as possible.

Thank you for your time.

ANSWER: Dear Luna,

Unfortunately they need to go to the vet. The tetracycline just isn't strong enough. The vet will probably put them on two, stronger antibiotics-- Baytril and amoxicillin. It should clear it up. Although your vet might say 10 days, I recommend 14.

It already is serious. Mice are prey animals, and so they do not show symptoms of illness until they are quite sick. A mouse can die of a respiratory infection overnight. They need to go to the vet right away.

Best of health to your girls.

Squeaks,

Natasha

---------- FOLLOW-UP ----------

QUESTION: Thank you for your advice; we'll be taking them to a vet first thing Monday morning. Meanwhile, I'm keeping a close eye on them and giving them steam baths to make sure they can breathe. They're reacting well to the steam already. I'll let you know what the vet says after their appointment.

ANSWER: Hi Luna,

I am glad they can get to the vet. Steam baths are just the thing. You can give them dark chocolate as well. Believe it or not, it helps with respiratory problems!

Squeaks,

Natasha

---------- FOLLOW-UP ----------

QUESTION: Update, with good news!
The vet said that nothing has spread to their lungs yet, and they should be fine. She put them on ten days' worth of Baytril, and she said she'd add a prescription for doxycyline if it becomes necessary.
Thank you again for all of your help. :)

Answer
Hi Luna,

10 days is not enough. You will probably have enough to give her 14 days, which is an absolute minimum. I do not know why so many vets under prescribe antibiotics. They may teach that in vet school, but people with rats know that illnesses often recur after only ten days' treatment.

Best of luck and health to both of them!

Squeaks,

Natasha