Let's not forget that the turtle is suffering, and probably has been for quite a while. Even if it is illegal to have, it is just as criminal to deny it proper treatment (it is a felony offense in many places). You have not only a legal obligation to get this animal proper veterinary treatment, but also a *gasp* moral obligation. If you can't take it to a vet, why the heck do you have it in the first place when EVERY animal will need to go to a vet SOMETIME? If every serious ailment had a homemade cure, why the heck do we have vets who spend 10 yrs of their life getting an education? The symptoms you describe sound grave in the most serious sense. Bottom line: If you can’t take care of it, give it to someone who will spare no expense to give it the best possible care, cuz there are plenty of people like that out there.
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...the oldest task in human history: to live on a piece of land without spoiling it."
Aldo Leopold (1938)
"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)