Definitely seem like Leeches to me, which is fitting.
This trailer has shown two enemies that definitely are animals, these leeches and the dogs, I wonder what explanation the game has for other animals being hostile enemies? The dog looks like a large Haunted, but these leeches just look like leeches, so I wonder what sort of role they have? The fact they look so normal has me suspicious they may have a much bigger role than one might guess, especially as leeches played a big part in Resident Evil lore. Like maybe when killing certain enemies they crawl out or something like that.
I've had a running theory for a while now that the reason the Haunted can keep on getting up even after their bodies are beyond sustainable damage to reasonably be alive is because something is inside them, controlling them.