the rats of venice are big, dirty bloodline rats. They have big dirty, diseased rat enemies and they all used Bouche deLion to eliminate - rat on - each other.
Whether the rats eliminated were the ones denounced, or the gossiping hell snitches who denounced them is unclear.
Unless you're a diseased rat yourself it doesn't matter.
https://www.nationalgeographic.com/travel/article/need-to-complain-heres-how-renaissance-era-venetians-did-it