Here's an example of a case we took earlier this year:
This is from a guinea pig named Trixie. Trixie was being fed bird food. You see the spots on her legs? That's where her starving body was cannibalizing her bones to try and meet it's desperate need for calcium. She died 2 days after intake. This was not prosecutable because the woman had, in good faith, provided food that she believed to be ok for guinea pigs. She was crippled and unable to walk and screeched in agony when she tried. This was in addition to her liquid diarrhea.
That's Gabriel. He was surrendered to us because he was "a little itchy" and they were moving. When our volunteer picked him up, he began having violent seizures in the car due to the severity of his mites. We had to stop transport to take him to an emergency vet to be injected with valium because his seizures were so violent. He died 4 days after intake. Not prosecutable -- she'd gone to the vet for him who said "he was fine". Our foster mom reported that he awoke her screaming in agony from violent seizures every 30 minutes.

This is BunBun. He was found
by a police officer living behind a school. He was in an outdoor, wire-floor hutch with a broken-in roof, mounds of droppings and dead chickens underneath, no water or hay, and moldy pellets. He was seized, but no charges were pressed.
I could post and post and post examples, and they would go on and on. The truth is, they happen so often that they barely rate any notice except when they are especially horrific, and isn't that sad? And yet, these are domesticated animals with readily available veterinary care and supplies -- not highly specialized exotics with complicated dietary, habitat, and medical needs.
I've got to say that, personally, no one in our rescue has ever heard of any of these cases being prosecuted, and we've been "in the business" for nearly a decade now. The ONLY times we've seen prosecution are in hoarder cases that also involve dogs, and these people typically get very light sentences. Actual, singular cases of abuse are very rarely prosecuted when they happen to exotics.