Well, I don't know if the Oct. issue of Reptiles is out yet but the cover story is about MHDs. (I wrote it)
If possible buy the issue and make him read that entire article from start to finish. I am betting that if you can see all of the bones that he hasn't had it treated for parasites yet and it won't be with us much longer anyway. I hate to see these wonderful animals suffer but I don't know what else you can do. You have tried to educate him and his parents either don't care of won't take the time to get involved so they won't provide much help either.
The only other possibility is your local humane enforcement. Some states have very strict abuse laws and actually enforce them. If you look at the links page of my site you can find links to the animal rights pages and see if your state is one of those that will protect the animals. If so you can try to get them involved by reporting this as a case of neglect. I don't know that this would be any better for the animal but it is bound to die at the hands of the 9-yr-old so it can't be any worse. If you are able to take this sort of action you may want to provide a copy of my caresheet so that they know what they are dealing with and can better evaluate the MHDs conditions and environment. I have found that most humane societies will take proper care of any animal, reptiles included, if they know what care is needed.
On the other hand, I don't want to see a young person's interest in Herps squelched, but he does need to learn that keeping reptiles isn't just a cool thing, but it takes knowledge, equipment, time, medication, and a real commitment to keeping that reptile healthy.
Hey, I know, show him some of these posts!
Marcia
www.froggieb.com/MHDLinks.html