snip invalid ecological argument

As for your question whether we must let them live just because they
are alive, the answer is simply yes unless there is a serious reason
forcing us to do otherwise. According to our values (at least the
Judeo-Christian ones) all life is sacred and one must have good reasons
to take it away. (For instance, with the Cane Toad to answer your
question, I might have no other option if it threatens me and my
family. There is no such danger from stray cats.)
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Check this link re toxoplasmosis :
http://www.cdc.gov/ncidod/dpd/parasi...oplasmosis.htm
The summary - it's a lot like glandular fever, unless you are
pregnant. In this case, there is a high chance of miscarriage, still
birth or massive birth defects. The disease is spread only via cat
faeces. Most commonly, the cat dumps in a garden bed and people then
contract it while gardening.
My wife contracted this when we thought she might be pregnant. There
is a wait of 1-2 weeks for all the tests, and let's just say that this
isn't a fun time in your life. While we were speaking with the doctor
about options, he mentioned that they had recently had a still born
baby in our area caused by a toxo. infection
We don't own any cats, but there are 3 'community' cats that use our
yard as a litter box.
My neighbour is currently pregnant and we have several friends
expecting and so any cat that we catch on our property meets a fairly
rapid end.

This isn't such a problem in the US, as most people already carry the
disease ( once you've had it you are immune to future infections ). In
Australia, it's relatively rare and therfore a much higher risk.

Anyways, one must realize that a decision to kill is a serious matter.
I didn?t see any such seriousness in the message to which I originally
replied.
Agreed. My reasons are the same as killing rats - the cats are a pest
that spread disease.

I suspect that all there is behind your arguments is that you just hate
cats and that you are afraid of anything not completely under your
control in your property and its surroundings. That?s fine but from
that to trying systematically to eliminate stray cats is a big step.
I don't _like_ cats, that's why I don't own one.
But, I don't hate cats. The same as I don't hate rats or mice.
Most of these problems would be solved if cat owners kept their pet on
their own property. Less chance of them contracting & spreading
disease, as well as less annoyance for others in the area.

In any case, you might want to try to find out why your emotions on
this issue are so intense. I don?t think the topic warrants such
intensity.