Thank you all for the education and especially for the link.

Unfortunately, this was not my decision to make. Katherine decided to send him to the Bridge.

There are three or four cats that live in the fields behind our warehouse. Between us, we have spayed or neutered them, and got them their first shots. We feed them every night but rarely even see them. Katherine was afraid that he would die in severe pain and we wouldn't be able to help him. She is going to see her vet today and discuss FIP with him in more detail so she will better understand.

Now that I know more, I would be inclined to agree with everyone here. I will definitely not end a life for only a positive FIP test.

I hope this thread will help anyone else who rescues a cat.