This guide will tell you where to find the Putrid Rat in V Rising.
On the Blood Altar, you can see that the featured rat has no track function, so it means you can’t track it. The only thing you can do is progress through the story and kill some of the earlier guys. After that, you can construct a vermin trap in the base, which will become a sort of resource-generating device if you have other resources to throw on it.
You have to pick the Putrid drive as it gives you rat form, and it is quite useful. After that, make your way into the room with the vermin box, and you will find the third option down to how to make the Putrid rat.
