Legionella: guide for gardeners

By KATHERINE HOBY

Legionnaires' disease is little-known in New Zealand yet four people died from legionella infections last year.

The disease is a type of pneumonia caused by the legionella bacterium which is found naturally in soil, compost, water storage tanks, cooling towers, and domestic water systems.

Many New Zealanders spend a lot of time in their gardens, and should be aware of simple precautions recommended to avoid contracting the disease.

The chief executive of the Nursery and Gardening Industry of New Zealand, Jeremy Kennerley, said potting mix was sometimes unfairly singled out as a culprit. There was no evidence to suggest the use of potting mix increased the chances of contracting the disease, he said.

"Gardeners are not at any greater risk than anyone else involved in an outdoor activity as long as they follow basic health guidelines," he said. "The public can be assured that potting mix manufacturers have taken a very responsible approach to standards and labelling."

He said potting mix was safe if simple handling instructions were followed carefully. Basic guidelines for handling potting mix:

* Wear gloves.

* Water the mix gently to avoid splashes.

* Opening bags of mix carefully.

* Dampen the mixture to reduce dust.

* Work in ventilated areas.

* Avoid bodily contact with unwashed hands.

Mr Kennerley said the legionella bacteria (Legionella pneumophila) could not be completely eliminated from the manufacturing process.

"Although any harmful bacteria could be killed off using a pasteurisation-type process, the side effect would be to wipe out the beneficial bacteria as well."

The disease begins with flu-like symptoms, and then moves on to high fever, shaking chills, headaches, diarrhoea, pneumonia and pleurisy.

It is contracted through breathing infected droplets of water or ingesting infected dust. Those at greatest risk are the elderly, those with immuno-compromised systems, and smokers.