mysterious death of ball python

Question
I got my ball python, Monty, around Christmas time. He was 10 years old roughly, and about 4 ft long, 5 inches around. We brought him home and he was fine. We went to a pet store and got him his first mouse from us. He ate it with no problem at all. When it was time to feed him again we went to a different place instead of driving to another town to get his feeders. The place we went was a local pet grooming shop that also sold small animals and feeder rats. We got a small rat and took it home to Monty and he ate it. Once again, feeding time arrives and we get him a rat. They gave us a black and white rat, which we had only fed him white rats before. He wouldn't eat the rat and we thought maybe it was because of the coloration of the rat. I ended up giving the rat to my uncle and going to Clips n Bows (the place we started buying from) and told them how he wouldn't eat it and they gave me another. Once again he refused to eat it. we tried multiple times and no result. I took the rat back and instead, got 2 mice thinking maybe the small feeder rat was too big. No luck. He wouldn't eat them. My boyfriend and I left for a day and checked on Monty before he left, he was fine. When we got back home we immediately checked on Monty. As soon as my boyfriend got him out of the tank, i knew he was gone. He wasn't stiff yet, so he must have just died. His tank was warm, fresh water, everything was fine. We went to clips n bows to tell the owner of the store what had happened. before we even mentioned the rats she jumped really quick to say there was nothing wrong with her rats. About a week before Monty died i noticed his belly started to have a pinkish discoloration. It wasn't time for him to start shedding, and we didn't have an under tank warmer. Unfortunately we don't have the finances to get an autopsy done at the time.
What the hell happened?! I've asked people that own multiple snakes and have owned them for their whole lives. Could it have been the rats or what? please help!!!

Answer
I'm sorry to hear of your snake's death. sudden death in an apparently healthy snake is probably the most frustrating and puzzling event to snake keepers.

It's unlikely to be the rats, although it does sound suspicious. it sounds like it was caused by the relocation of the snake. Long term captive snakes may stop eating or die suddenly when switched to a new location, even if the location has ideal conditions. This is usually due to bacterial overgrowth in the gut, leading to gastroenteritis or septicemia. Bacterial overgrowth is commonly related to stress, which lowers the body's ability to fight infections etc. through immune system suppression.

Another possibility is an intestinal parasite that Monty may have carried before you got him. These parasites penetrate the intestine and cause internal bleeding and peritonitis -(Although i don't know for certain this may be what caused the pink discoloration on the underbelly). These parasites can be diagnosed by spotting blood present in the feces. If you can remember seeing any blood in your snakes feces this may be the cause of his death.

Other than that, under the circumstances there are very few other possibilities of reasons for your snake's death. Only a necropsy may be able to tell for sure and even then it might not always provide a clear reason.

Thanks for your question,

Andy