I haven't seen any lethargy. She sleeps, but that's normal. She isn't sleeping excessively and she plays all the time if the lights are off. Her fur looks normal and the only time I've seen porphyrin was when I had a flat paper floor in their cage while potty training them and there were some light pink marks around their bed. Didn't seem like an abnormal amount. I just checked her breathing and while I couldn't hear very well since she was squirming [she's not entirely used to being handled yet] it sounded like normal to me. Just windy breathing sounds.
If the only symptom you see at all period is this noise, I wouldn't worry. You gotta get them out of that bin as soon as humanly possible though.
The second she gets worse it's time to go to the vet. It's possible this is all because of the bin / lack of air circulation. It might get better when she can breathe better, or it could develop into a solid URI.
Lethargy is identifiable moreso by lack of interest. Like if you try to play with her or give her a treat and she just doesn't move or care. If any of the symptoms I mentioned or any of these show up, go to a vet:
- Eating less
- Drinking less
- Wheezing, clicking or coughing noises
Keep listening to her lungs everyday, the best you can. If you hear anything besides a soft woosh-woosh it's a problem. For porphyrin, you should only see a small amount around the nose when they first wake up.
Oh and vet costs... I'd say expect anywhere from 25-100 $ for the visit and actually about the same for antibiotics to treat a URI. It really is too hard to guess if we don't go to the same vet. My advice is to call all local vets who see rats and ask how much a standard exam fee is. Antibiotics for URIs really should be less than 50$. You can ask how much they charge for antibiotics, but the receptionist might not know. This is good information to have either way!