Not too sure that isn’t still in use.
I’ve got some ideas about how to rid cities of rats, and NYC would be a great place to start working on it, with its billion-ish rat population.
And ahead of time, I’d be preparing a huge breeding population of voles (North America’s native relative of the hamster and lemming) to fill the niche vacated by the rats, to keep them from regaining a foothold.
The voles were in epidemic proportions around the area where my folks live. They damaged a lot of the spud crop down there. Our cat caught a lot around here last summer. She just leaves them dead on the doorstep.
All the Health and Welfare has to do is pop out a new food pyramid with a rat at the top and problem solved.
I was reading the rats were getting resistant to Warfarin.