Where to report depends on where you live. In my county reporting abuse/neglect of anything except dogs or livestock to animal control gets a non-response due to lack of resources. For reptiles I've been called because they just don't have the proper enclosures and staff versed in how to care for them.
Some states also regulate pet stores, you can see if yours requires permits or licensing with husbandry standards in place, and which agency is responsible for enforcing them.