I am so sorry about your poor dog! It sounds as if your vet is doing a great job. A poisonous spider or other insect bite could cause a problem as you have described. Dogs will bite all kinds of things to eat and as defense and occasionally get stung or bitten on the tongue. Necrosis of the tongue surrounding the bite or sting occurs when the area actually dies off. This does not mean that the entire tongue will fall off or that your dog will do badly from this. The necrotic part of the tongue may have to be removed surgically to expidite healing. Please ask your vet about this. In the mean time continue to feed and care for your dog as you have been.
Dear Dr. Cheng, Thank you so much for your kind words and encouragement. You are right, our vet has been wonderful, checking on our dog and giving him antibiotics every day. After several days it became clear that our dog was going to lose a part of his tongue. His tongue actually split in front so he looked like he had a viper tongue as the healthy tissue separated from the dead (wish I'd taken a picture now but it was too traumatic at the time!). At that point our vet injected him with a spider poison that sped up the process of losing that part of his tongue (he told us they also use this venom for breast cancer treatment!).
The next day, the dead part dropped off and the horrible smell went away. He told us to keep a close eye on our dog to make sure there wasn't much blood loss when the tongue did drop. Thankfully, there was hardly any blood at all. By that night, he was able to eat soft food on his own and now he is learning to lap up water too. It's been quite an episode but we are very grateful that our dog is going to be alright and for the excellent care he received.
All in all, there were six vet visits to our home, one visit to the vet's office where he administered an IV, about 14 injections (mostly antibiotics, initially an anti-inflammatory), 4 cans of soft food (Science Diet), and a medicine to put on his tongue. Total cost for everything was approximately $215. Yes, you read that correctly. He's also given us great advice for dog training. So, we thank God and our vet for a happy outcome. Thanks to you as well for the reassurance that this was handled well.