Take a look at this story of a very large cat being effected by rat poison: http://tinyurl.com/ovoauml
They think it ate dead rats killed with poison. When I was a kid, we lost 1 cat to what my parents thought
was poison. Another just did not come home and I found a cats body a while later. Didn't want to get close.
But, I think it was our cat. My guess is she was killed by poison.
Any ideas how to keep cats away from rat poison? Besides keeping inside all the time.