This looks to be a midland watersnake (also known as banded) They are often confused with the cottonmouth as they can be quite similar and share the same habitat. Removing a snake like this from the wild, without reason or knowledge is pretty silly.
they are also known to have a pretty nasty disposition. They will also secrete a musk when on the defensive, which is never fun.
i don't know about Illinois, however I'm fairly certain they are protected by state law in Georgia against killing or capture, but you would need to look into that.
most wild caught snakes are often riddled with parasites in the wild. It's just somthing they deal with, this snake is normally quite heavy bodied too, which makes me believe this snake in particular is likely housing internal parasites itself.
in my humble opinion, do yourself and the snake a favor and release it where you found it. And go buy yourself a captive bred, "pet" snake.
all the best
"edit" I read your state as Illinois not Indiana, outside that and the genus the rest of the post still stands
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