A hidden danger in the garden has been highlighted by the case of a man who contracted Legionnaires' disease from handling compost.

Doctors discovered that the 67-year-old man was infected through a cut in his hand.

Reporting the "rare" incident in The Lancet medical journal, they said compost was known to harbour Legionnaires' bugs.

The man, described as previously fit and healthy and a "keen gardener", was inexplicably struck down by a serious fever in March.

Doctors saw him in hospital after eight days of trembling, confusion, lethargy and shortness of breath. He had a high temperature and an X-ray revealed signs of pneumonia in his left lung.

Dr Simon Patten and colleagues from the Royal Alexandra Hospital, Paisley, Scotland, wrote: "We treated our patient with oxygen, intravenous fluids and antibiotics, but his respiratory function deteriorated, necessitating transfer to the intensive care unit for intubation."

"When we questioned the patient to find out the source of this infection, we discovered that he was a keen gardener and had lacerated his left index finger two days before the onset of his symptoms, while planting with compost," they wrote. "We presumed that this cut was the site of entry of the organism."

The patient's condition improved, and seven days later he was moved to a respiratory ward before being discharged.

Legionnaires' disease is normally caused by the bug Legionella pneumophili, which lives naturally in rivers, lakes, and reservoirs, and can also be found in man-made structures containing water such as air conditioning systems. Legionella longbeachae is a less common species first isolated from a patient in Long Beach, California. Unlike its cousin, it is mostly found in soil and potting compost. Infection by this type of Legionnaires' bug is sometimes called Pontiac Fever.

In the UK, just nine cases have been reported since 1984. L. longbeachae infections are much more common in Australia, New Zealand and Japan, where it accounts for about 30% of all cases of Legionnaires' disease. They added: "The UK Royal Horticultural Society has issued warnings about the risk of contracting Legionnaires' disease from handling compost and has announced that bags of potting compost will carry cautionary statements."