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Gardeners compost a source for legionella bacteria

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Gardeners are being advised to wash their hands after handling compost following a series of Legionella cases in Scotland.

One person has died and five others have become ill after being exposed to the Legionella longbeachae organism. Health Protection Scotland said three of the cases have been confirmed, two were probable and one was possible. Five of the cases involve keen gardeners.

There are two causes of Legionellosis:

  • Legionella longbeachae, which is found in potting mixes, compost heaps and composted animal manures
  • The more common L. pneumonophila, which is commonly found in hot water systems, air-conditioning cooling towers, hot and cold water taps and showers.

Experts are unclear about the way in which Legionella longbeachae spreads. The bacteria may be breathed in or spread from hand to mouth. Legionella longbeachae can remain on hands contaminated by handling potting mix for periods of up to one hour. Evidence from Australia has highlighted the importance of hand-washing after handling compost.

A spokeswoman for the Health Protection Scotland said of the five gardeners involved, all had spent a major proportion of their time dedicated to the hobby. Cases tended to be in older people with underlying health problems, or people who smoked.

The statement from the Health Protection Scotland added that “no specific gardening activity (e.g. potting) or type or source of compost have been identified as common to all – or almost all – of the cases and therefore as being the likely source of the infection”.

Health Protection Scotland said its advice to gardeners was to wash hands thoroughly after carrying out gardening tasks and before eating or smoking. It said it was investigating whether further precautions for gardeners needed to be drawn up.

The Growing Media Association (GMA) said it was aware of the reported links between Legionella longbeachae and potting compost. In an emailed statement, a spokesman said: “We have been working with Trading Standards, microbiologists and medical advisers since these concerns were first raised in the UK.

“The GMA is committed to acting in a responsible manner on this important issue and is therefore conducting a detailed global analysis of the situation. Once the full results are available, the GMA will consider what advice it should issue to consumers, and whether labelling of bagged compost is appropriate.

“It should be noted that there have been only 11 reported cases of Legionella potentially connected to the longbeachae microbe in Great Britain since 1990. As a result there is an extremely limited amount of data available to those investigating the circumstances surrounding these reports. The exceptional rarity of these reported cases would seem to indicate that any associated risks are minimal.

“Despite this early indication, GMA members consider that the safety of their products is of paramount importance which explains our comprehensive approach to this issue”.
Source: Peter Russell
WebMD UK Health News

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