Print

Email story

Comment

Email editor

Garden

Danger down under

Florida gardeners have their share of potential perils in the garden, including snakes, spiders and stinging insects. But there are other threats lurking underground that could be far more serious - even deadly.

By Yvonne Swanson
Published January 28, 2006

[Photo: Yvonne Swanson]

Wearing gloves when working with soil and washing your hands when you are done can help you avoid an array of disease-causing bacteria that can be found in your garden.

Soil is a living organism composed of solid particles, minerals, organic matter, water and air. It's also a breeding ground for all kinds of harmful bacteria, parasites, fungi and substances such as lead and arsenic.

There are thousands of bacteria that occur naturally in the environment. Some are good because they protect plant roots and enrich the soil; others are bad and can cause illness, including Clostridium tetani, which enters the body through a puncture wound or open sore and can cause tetanus. Although the incidence of tetanus in the United States is low, a significant number of cases are attributed to outdoor work. According to the federal Centers for Disease Control and Prevention, 31 percent of 130 U.S. tetanus injuries reported from 1998 to 2000 were sustained in the yard, garden or farm. A potentially fatal disease, tetanus often begins anywhere from three to 21 days after exposure by causing stiffness in the neck and trouble swallowing. If left untreated, it leads to painful muscle spasms and eventual death. If you're current on your tetanus immunization - the CDC recommends a tetanus booster every 10 years - you're protected. However, fewer than half of U.S. adults have the proper immunization and only one quarter of adults over 70 are immunized, says Dr. Susan Rehm, an infectious disease specialist at the Cleveland Clinic and medical director of the National Foundation for Infectious Diseases.

Tetanus is just one of numerous disorders that can result from contact with infected soil and mulch, says Rehm, who has treated patients with a variety of fungal and bacterial infections that originated in the soil or garden water features, such as fountains, bird baths and ponds. Some illnesses come from contact with plants themselves, including sporatrichosis, a fungal infection associated with handling sphagnum moss, says Rehm. "It has a characteristic rash that looks like nodules or bumps," she says. Don't panic, however, because most garden-related infections can be prevented by practicing common-sense measures such as wearing gloves, washing hands and bandaging cuts, says Rehm.

But according to a recent Reuters news report, 24 people in Singapore died from a soil-borne bacterial infection called melioidosis, or Whitmore's Disease, which can enter the body through the nose or broken skin. Open wounds were found to be the source of transmission among hundreds of U.S. soldiers who contracted Acinetobacter, a deadly drug-resistant bacteria that originated in Iraqi soil.

Granted, those cases are extreme, but they might make you think twice before digging in the soil with bare hands or romping around the garden in bare feet - especially if you are pregnant, elderly or have a compromised immune system due to chemotherapy, HIV or other disease that puts you at higher risk for illness. Parents should be particularly cautious with very young children who may ingest soil.

That's the advice from Dr. David Mellard, a toxicologist with the CDC's Agency for Toxic Substances and Disease Registry, who notes that eating soil isn't uncommon for children less than 2 years of age; it is also found in older children with an eating disorder called pica. But adults can just as easily ingest harmful agents simply from poor hygiene. "A lot of it depends on personal habits. Someone who gardens and doesn't use gloves, then bites their nails, is at risk," says Mellard.

Florida soils are not considered at heightened risk of arsenic or lead poisoning, says Mellard, although arsenic could be present in the soil immediately in contact with pressure-treated wood used for garden bed edging, raised beds and other outdoor structures. Arsenic, a known carcinogen, can enter the body through ingestion or cuts in the skin, he says.

Prior to the U.S. Environmental Protection Agency's voluntary phase-out in late 2003, most outdoor residential wood products contained chromated copper arsenate, or CCA, a chemical wood preservative made of chromium, copper and arsenic. According to the EPA, the chemicals can migrate from treated wood into surrounding soil at different rates depending on factors such as rainfall and acidity of soil.

"I would be concerned mostly for children who eat the soil . . . You don't know the levels of the arsenic or chromium in the soil," Mellard said.

Another bacteria source that might come as a surprise is your outdoor cat. Your garden could be littered with cat feces loaded with millions of toxoplasma gondii parasites that cause toxoplasmosis infection. More than 60-million people in the United States have the parasite, but most are symptomless other than initial flulike symptoms. The greatest risk is to people with weakened immune systems, who may then develop damage to the eyes or brain, and infants, who when infected in utero can have serious birth defects. Toxoplasmosis can be detected with a blood test and treated with medication. Reliable tests for cats are not available, according to the CDC.

Feces from cats and dogs can also be a source of parasitic roundworm diseases, which are more common in warm climates such as Florida. The eggs or larvae thrive in the soil and can enter the body through the skin or mouth, usually making their way to the intestines, where they cause a variety of health problems. There are many types of parasitic diseases, symptoms and treatments.

Excrement from pets, including cats and dogs, should never be used as manure or in composting because parasites are extremely long-lasting, horticulture experts say. If you're using manure, perhaps from a local horse stable or farm, dangerous bacteria could be present if the animals are infected. This can pose a serious threat, especially in a vegetable or herb garden. Your best bet is to use commercially bagged manure, which is composted and should be free of contaminants.

A good way to judge if compost is healthy is to examine its color, texture and aroma, says Charlie Nardozzi, senior horticulturist at the National Gardening Association. It should be dark brown, crumbly like soil and smell earthy - not like sulfur or ammonia. Don't use it if it's wet. If you do plan to work with fresh manure, let it mellow. "You should compost it first. In a warm climate, it might take only a couple of months. In a colder climate, give it an entire growing season," he says.Yvonne Swanson is a freelance writer in St. Petersburg and a master gardener for Pinellas County.

[Last modified January 27, 2006, 17:04:35]