I have a rat (named Possum) who is nearly 5 years old. (Yes, I'm sure on her age.) She is very old and keeps getting respiratory infections. She wheezes and sneezes and sounds like she's got a smokers cough. Her eyes and nose leak that gross red fluid, which I wipe off gently with a warm wet cloth. I've given her medicine before but it didn't work. Multiple medicines for several weeks on and off for about a year and the infection wont go away. Thing is, she may look and sound terrible, she acts fine. Eats, drinks, sleeps, plays, etc. When she's on any medication she acts very sick. She refuses to eat and drink and sleeps all day. It seems like she's very sensitive to medicines. Should I continue treating her? Let her live as she wishes? Put her down? I'm inclined to leave her as she is because the medicine makes her so ill and she seems to not be in pain or anything. Even looking and sounding so sick. Could it just be old age? I change her bedding every day because she's housed with three other rats. The other three have never caught whatever she has (though I did quarantine at first but the vet said after a while of medicine to reintroduce her).