Is it my fault?

[Caitlin]

God, I am so sorry this happened.

I am not a veterinarian; I was raised in a family of vets and worked my way through undergrad and grad school as a vet tech in exotics and laboratory settings. So it is very possible another member here will have better info than I do.

You clearly kept her successfully for many years. Still, after losing an animal I think it's always a good idea to take a close look at husbandry - it's not hard to have some critical element (temps, humidity, environmental stresses) slip out of control for a bit, and sometimes that's all it takes for the opportunistic bacteria, fungus, or viruses that are always present in the environment to take advantage of the situation. That said, I don't think you should blame yourself - you got her to the vet and followed the instructions you were given. The fact that she refused food is normal for snakes undergoing antibiotic treatment or who are struggling with a respiratory infection.

This is the hard part - please know that I am not being critical of you. I have lost beloved snakes myself. Reptile vets don't generally regard oral antibiotics as ideal for RI, though they are used sometimes. Ideally you'd want the vet to take a culture via a lung wash or tracheal swab to determine exactly what type of bacteria were involved, and then prescribe an antibiotic known to be most effective against that specific type of bacteria. I have to admit I have not often heard of doxycycline as the first choice antibiotic for RI. These days you'd typically see RI treated with injections of Ceftazidime (Fortrum), Cefotaxime (Claforin), or somewhat less often, Enrofloxacin (Baytril).

So in future - and I do hope that you find yourself willing to invite another snakey friend to your family someday - you might consider establishing a relationship with a reptile specialist veterinarian, or at least have one available that your regular veterinarian can consult with. None of this means that your snake got bad treatment, but I will admit I am a little uneasy about what you describe. She wasn't my snake, though, and you know your own veterinarian, so I don't want to jump to conclusions here. I just felt like I should share this info for your consideration.