On 3 Sep, 14:49, "Ian B" wrote:
David in Normandy wrote:
Quote: "Compost manufacturers are considering putting warnings about
Legionnaires' disease on their bags following advice from the Royal
Horticultural Society."

The full article:
http://www.telegraph.co.uk/health/7978133/Potting-plants-could-cause-...

Personally I enjoy getting my hands into the compost, it is half the
fun of potting up plants!

Hmm, I vote "dubious" for the claims of this article. I have some knowledge
of legionella as I used to be a building services engineer (polite term for
maintenance man) and a significant part of that is legionella precautions.

Legionella bacteria is all around us in the evironment. It's in all our
water. It is, under normal circumstances, harmless. It only becomes
dangerous when inhaled in a fine water spray, at which point it is able to
circumvent the body's natural defences against bacterial attack. We must
remember that the environment is full of things that want to do us harm,and
the reason we're here as a species is that the body has over billions of
years of evolution developed all kinds of protective mechanisms; which is
why disabling the immune system causes a horrible death from opportunist
infections. Once your protections are down, it's not *if* you will get ill,
but *when* you will get ill.

This is based on one particular case, and a supposition by the doctors
treating the man. It's a guess that he caught the infection from compost.
They have no proof, and cannot have proof; the only facts they have are that
he caught legionella, and had handled compost with a cut hand. But
correlation does not equal causation. He might have caught it from a spray
of water he does not even remember to tell them about.

So far as I am aware there are no known cases of legionella (except this
one, now, apparently) in which it has been caught by this route of
infection, through a skin lesion. If legionella were capable of infecting us
this way, it would be epidemic. But it isn't. Just rinsing a cut under tap
water- a very common first aid- would lead to infections, from legionella
infected water getting into the cut. Swimmers would catch it. People
handling garden soil would routinely catch it. Farmers dealing with water
troughs for animals would catch it. And so on.

But they don't. It is even very hard to catch from fine water sprays. Only
very high concentrations of the bacterium combined with a lack of water
treatment cause outbreaks. It only became a threat when cooling systems
using water sprays became commonplace, an environment in which the bacterium
thrives as the water is in a closed loop and can thus build up bacterial
concentrations; which is why engineers have to have a regime of bromine
treatment.

So I call foul on this. It's a supposition, not a scientific conclusion;
just guesswork from a doctor. It seems very unlikely to me.

Of course it's always advisable to avoid getting a cut dirty. There are lots
of diseases that like to make their way into the body via a dirty wound.
Legionella isn't one of them.

Ian

All of the above is exactly so.
I was a hospital engineer and spent quite a time bothering over
legionella.
You are more likely to get legionnaire disease by taking a shower.
About the compost, problems have arisen since substitutes for peat
have been incorporated. Peat was fairly sterile. Stuff like coir and
even composted human excrement are now used. I suppose there's a
good chance of infection via a cut.