Is the turtle even alive anymore? Looks like his shell's cracked in a few places and infested with maggots; I'd probably soak the turtle in lukewarm water first for a couple minutes, then place it in a diluted chlorhexidine bath for maybe 10 or so minutes; hopefully that might clear the maggots from the wound and disinfect it a bit. I'm not too sure about this, but soaking the turtle in water with aquarium salt added could possibly also help. I know it'll probably remove a large portion of the maggots, though. I don't have much experience with terrestrial turtles, but if you can somehow clean the wound and remove the maggots, Betadine, Polysporin (without the painkiller additive), and some sort of iodine-based topical cream might be beneficial. Canine saliva might prove to be greatly detrimental to the turtle; possibly lethal (although I highly doubt it). Honestly, I think it would be best just to turn the poor turtle over to an animal rescue of some sort if there's any in your area. 90% sure the turtle is an Eastern Box Turtle.