Legionella News – Compost Threat


The Scottish study looked at 22 different brands of compost bought at shops in the UK. A variety of Legionella bacteria were found in 14 of the composts. Four brands contained Legionella longbeachae.

Human Legionella infection has already been linked to compost in Australia and New Zealand and last month Health Protection Scotland said NHS Lothian was investigating four cases of Legionella longbeachae linked to gardening compost.

Legionella longbeachae - an unusual form of Legionella can cause a wide range of symptoms from mild flu-like illness to pneumonia and death. The major source of human infection is considered to be potting mixes, compost heaps and composted animal manures. Older gardeners and those with a suppressed immune system are most vulnerable.

Changing composts

This latest research, conducted at the University of Strathclyde, suggests that the Legionella bacteria found within the composts tested could be a source of infection.

Dr Tara Beattie, who led the research says in a press release: "Disease causing micro-organisms are widespread in the environment, and therefore it is not too surprising that species of Legionella that can cause human disease are present in compost.

"Any environment where you have pathogenic bacteria could be a source of infection, and we already know that compost has been linked to human Legionella infection in countries such as Australia and New Zealand.

"Within the UK and across Europe composts have traditionally been composed of peat, whereas sawdust and bark are more often used to produce compost in Australia and New Zealand where Legionellosis associated with compost is more common.

"It may be that the change in composition of composts in the UK, moving away from peat based products, could be resulting in species such as Legionella longbeachae being present in compost and therefore more cases of infection could occur."

However, Dr Beattie added: “It should be emphasised though, that although Legionella seem to be common in compost, human infection is very rare, especially if you consider the volume of compost sold and used.

“But with any potential source of infection precautions should always be taken. The occurrence of these bacteria in composts in Australia and New Zealand, and the cases of infection that have been traced to compost has resulted in hygiene warnings on compost packaging in these countries, and this is something manufacturers in the UK may wish to consider."

Safe Handling Advice

The advice for anyone using compost is to always wear gloves, avoid inhaling dust from compost particularly in enclosed environments like a shed or greenhouse, and to make sure you wash your hands after handling compost and before smoking or eating.