Boa Health Declining Quickly- Advice Needed

[Bogertophis]

That's an awful lot of weight loss & I'm sorry to say it sounds pretty serious. I think a vet visit is what you need- this doesn't sound like a husbandry issue, unless he was ever over-heated??? (Excessive heat can cause neurological damage to snakes- but you said you're using t-stats & all that.)

Was he fed live rodents? Either by you or before you got him, IF you know? I ask because live rodents can share parasites like intestinal worms that steal a snake's food & health. But this could be something else & I don't wish to speculate. It's not appropriate or ethical to diagnose a seriously ill snake over the internet that we haven't even seen in real life, even IF we were veterinarians, which we are not- some of us are long time keepers & breeders of snakes with many years of experience, but that's all, so please believe me when I say you need some lab work done if you hope to save this snake. Waiting = more risk. Sorry if it's not convenient, so much of life isn't.

If you need more vet options: https://arav.site-ym.com/search/custom.asp?id=3661

Your initial vet check-up wasn't likely to turn up anything- snakes are too stoic for that, so unless they did real lab work (blood & stool) & for actual symptoms, they were just re-assuring you with very little information to support their conclusion. Pet stores have tons of temptation, but keep in mind that their unfortunate animals have often been shipped to them from a long ways away under crowded & very stressful conditions (that weakens their immune system) & with exposure to both captive-bred & wild caught, native & non-native reptiles, some of which are likely to be ill or carriers of diseases & parasites- so bottom line, it's a risky place to buy a snake. In the past, when I was a new keeper, I have done so also, but it takes "luck" too.

Good luck, I hope you get him some help, quickly. I'll admit that IBD crosses my mind too- pythons tend to get very sick much quicker whereas boas can have this for a while before becoming symptomatic. Sure hope that's not what it is though- again, you need professional vet help on this.