Mary Alice, testing for Tg in a cat and releasing them will NEVER get rid of the Toxo and also will NOT prevent further predation by the cats.  If you surround them with a predator proof fence, then they are contained, but cleaning up thousands of litter boxes everyday is NOT a reality.  You don't understand the lifecycle of Tg and transmission.  By the time a cats serology turns positive, it has already shed over a million infectious oocysts into the environment.  Euthanasia is humane, prevents Tg spreading further, and prevents further predation.  Ecologists need to be involved, NOT amateur cat trappers, because not only are cats tough to trap (or shoot), but the introduced rodents have to be controlled too.  There are now non-toxic rodent traps, self emptying, and self reloading, but real scientists need to design such a comprehensive approach.  Agree the community has to be involved, but they should take pride in saving local species, while keeping their own cats safe at home.