Garden Variety Illness? Man Survives Freak Legionnaires' Infection

Sept. 3, 2010— -- Pity the poor British fellow who learned that puttering in the garden can be, in rare instances, hazardous to one's health.

Researchers have published a case report involving a 67-year-old man admitted to a hospital in March after spending eight days suffering from fever, shortness of breath and confusion. The doctors' diagnosis was pneumonia, but they were at a loss to find the underlying cause, according to the report this week in The Lancet.

Initial tests came back negative for several pneumonia-causing viruses. But a fluid specimen taken from inside the man's lung cultured positive for a rare strain of Legionnaires' disease -- the potentially fatal and eponymous respiratory illness named for a 1976 outbreak among American Legion conventioneers in Philadelphia that sickened 221 people, including 34 who died. Legionella bacteria most often spread through tiny droplets of water spewed from cooling towers, hot tubs, showers or -- in the 1976 outbreak -- air conditioning systems. They do not spread from person-to-person.

In the British case, though, doctors were trying to figure out how a man who tinkers in the garden could become infected with typically airborne Legionella.

Further investigation revealed that the patient had cut his finger while composting two days before his symptoms began. Several published cases in Australia, New Zealand, Japan, the Netherlands, Switzerland and Scotland, as well as California, Oregon and Washington state, involved men and women who used compost mixes, compost heaps and potting mixes to plant tomatoes or bulbs, and contracted a strain called Legionella longbeachae, isolated in 1981 from a pneumonia patient in Long Beach, Calif. Subsequent tests in those cases confirmed the presence of Legionella in potting soils they handled.

Fortunately, the gardener responded to antibiotics. But the case has ongoing ramifications. The Royal Horticultural Society in Great Britain has issued warnings about the possibility of contracting Legionnaires' from touching compost and will begin posting cautionary advice on bags of potting compost.

Compost Key in Gardening-Linked Legionnaries' Disease Case

According to the federal Centers for Disease Control and Prevention in Atlanta, about 8,000 to 10,000 Americans are diagnosed with Legionnaires' each year. But that's widely considered to be the tip of the iceberg. "The number of cases is much higher since most of the time it is not looked for, the diagnosis is hard to make, and the usual antibiotic coverage for community-acquired pneumonia will take care of it," says Dr. Peter Katona, an infectious diseases specialist at UCLA.

Because it starts like many other types of pneumonia, with a high fever, chills and cough, it can easily elude proper diagnosis. Anywhere from 5 percent to 30 percent of cases end in death, but most sufferers recover with antibiotic treatment. The elderly, those with weakened immune systems, and people with lung disease are especially vulnerable.

A 2009 study published in the journal Clinical Microbiological Infection described potting soils as an important, but probably underestimated, source of Legionella infection, by L. longbeachae as well as other Legionella species associated with Legionnaires' disease. Katona says that the source of the bacterium -- either soil or water -- or the species isn't what determines how sick you can get. Instead, he says, it's "the magnitude of the exposure, the virulence of the bug, and the fact that it gets into both blood and lung as in this case."

And Legionnaires' disease isn't the only illness spread this way. Said Katona: "Soil and plant exposure also causes other diseases such as atypical mycobacteria and sporotrichosis." (Atypical myobacteria, which are in the same family as tuberculosis, cause a wide variety of infections, while sporotrichosis is a fungal skin infection).

Add to that list aspergillosis. In 2008, a 47-year-old British welder became sickened after opening bags of old gardening mulch that emitted a cloud of dust. That cloud proved toxic, as it contained spores of aspergillus, a common fungus that doesn't bother most people. But the welder who inhaled those spores developed aspergillosis, which landed him in an intensive care unit as his lungs shut down, and he died within days. Because of such mulch hazards, some doctors advise patients whose immune systems are weakened by chemotherapy, or immune-suppressing drugs, to stay out of their gardens.