Soil Borne Diseases – Does Soil Make Gardeners Sick?

A few times a year I’ll see a meme float through social media telling gardeners they can die from soil borne diseases. The most recent of these was one for Legionnaires’ disease in New Zealand. I have also seen them for Tetanus, and I recently got my booster shot, just to be sure. For years I’ve been reading that sphagnum peat moss also carries a nasty bug.

As I write this, the news is saturated with information about the coronavirus and people are suiting up with masks and body armor. Should gardeners be doing the same thing when they head out into the garden? Should we wear masks and latex gloves to stay safe?

I decided to write a blog post about soil borne diseases that gardeners can get and try to uncover the myths about them. I expected to find 4 or 5 diseases and write a bit about each one so that I could try to understand this problem better.

You will be very surprised at what I found.

Death by Soil Exposure

Lets narrow the scope of this post. Gardeners face many deadly challenges including hazardous pesticides, poisonous plants, heart attacks due to over exertion, poisonous spiders and snakes, and allergies, but this post will only deal with diseases that gardeners can get by exposure to soil microbes.

Too Many Soil Borne Diseases

When I started this research project I expected to find a half dozen diseases but I was blown away by the many diseases you can get from soil. There are so many that I can’t possibly fit them all into a single blog post so I won’t even try to list them all. Here are some interesting ones to give you a taste of the danger below your feet.

Valley Fever occurs when people inhale fungi that belong to the group Coccidiodes, which are found in the southwestern United States. The tiny spores live in desert dirt, and on windy days, they can get blown around and you breathe them in. Severe cases can lead to pneumonia.

Hantavirus has a high mortality rate and is spread by rodent droppings, urine and saliva. It can become airborne and infect gardeners.

“There were 233 tetanus cases in the United States during the years 2001 to 2008, with a 13% fatality rate.” It is a significant cause of death in Asia, Africa and South America. “In 2006, 290,000 persons died of tetanus globally, of which 250,000 were neonatal deaths.” The bacteria causing tetanus is common in soil, dust and feces.

Botulism is well known as a disease related to infected food, but “wound botulism” can be contracted from soil.

The brain-eating amoeba kills almost everyone infected. The single celled microbe is found in warm freshwater and needs to enter the body through the nose. Unless the gardener goes for a swim in their pond, they should be safe.

Several strains of Escherichia coli (E. Coli) cause diseases. One strain, ETEC, accounts for several hundred million cases of diarrhea and tens of thousands of deaths globally each year.

Melioidosis is a bacterial infection that quietly causes thousands of deaths each year as people come in contact with mud.

And lets not forget the helminths, a group of parasitic worms, many of which live in your intestinal tract. They are usually contracted through exposure to soil and “approximately 1.5 billion people are infected worldwide.”

The fungus Histoplasma, which causes lung infections, is spreading throughout the US and probably other countries as well.

A good summary of many diseases can be found in “Soil Borne Human Diseases“, which is available on the internet.

Rate Of Infection

There are lots of diseases and lots of potential exposures, but to really understand the risk we have to look at rates of infection. There is some data for the EU (European Union) showing about 31 infections (includes all soil borne diseases), per year, per 100,000 people. It is possible that the rate of infection among gardeners is higher.

To put this into perspective, 5,000 out of 100,000 in the EU get influenza each year, resulting in 8 deaths. We don’t all go around wearing gloves and masks to prevent catching this disease.

In the EU, and most industrialized countries, the flue is a much bigger problem than soil borne diseases.

How Do We Get Infected?

Two things need to happen for infection to occur. Firstly, the offending organism has to be present in the soil. Many of these organisms are ubiquitous. Some are more prevalent in certain climates, but they do readily move around, so assume they are present.

The organism needs to enter your body. This can happen through a cut in the skin, through the mouth or through the nose. Many air borne fungal organisms and bacteria travel easily through the air.

If you don’t touch the soil and stop breathing, you are safe!

For example, tetanus is caused by a bacteria called Clostridium tetani, which lives in soil and manure. Infections occur through cuts and scrapes caused by things in contact with the soil, such as garden tools or rose thorns.

Contaminated Food

You have all heard the recalls for contaminated food, but what you probably don’t realize is that the organic food you are producing in your vegetable bed is just as likely to be contaminated from your soil. The difference is that you don’t test your garden produce, so you don’t know if it should be recalled.

Sterile Soil

There is not much you can do to eliminate these  diseases from the soil in the ground, but what about sterile soil used for containers. Is it safe?

To start with, there is no such thing as sterile soil except in a lab where it is specially treated. Those bags of soil that say “sterile” on them, are not sterile. See Sterile Soil – Does it Really Exist? for more details.

Legionnaires’ disease got a lot of publicity when some deaths among gardeners were attributed to it. Commercial potting mix was blamed. Since that event, it has also shown up in Europe and North America and seems to be on the rise as people are using more wood-based soils instead of peat-based ones. A study found 26 (79%) of 33 potting soil samples in Australia, tested positive for Legionnaires’ disease.

Assume that all soil, bagged or native, contains disease organisms.

Organic Manure

Different organisms live in manure, but many of the soil borne diseases humans get, exist in manure, and adding it to soil generally increases the number of disease organisms and increases your chance of infection.

So much for that great organic manure 🙂

Peat Moss

I have often read that peat moss is sterile. That of course is nonsense, but it does contain fewer microbes than soil because it is not a great environment for them (acidic with few nutrients).

It may surprise you that sphagnum peat moss can make you sick with the “rose gardener’s disease” (Sporotrichosis), which is caused by the Sporothrix fungus. This fungus lives in soil and on plant matter, including sphagnum peat moss, rose bushes and hay. Skin infection, through cuts and scrapes, is the most common way to get the disease. In Brazil, people have gotten sporotrichosis from contact with cats.

How common is sporotrichosis? The CDC estimates that in the US the annual rate is less than 1 person, per million population. “In the spring of 1988, the largest documented US outbreak of cutaneous sporotrichosis to date occurred, with 84 cases among persons from 15 states who were exposed to Wisconsin-grown sphagnum moss used in packing evergreen tree seedlings.” The moss source tested negative, but one nursery using old moss tested positive.

I think I’ll stop worrying about death by peat moss!

Preventing Soil Diseases

Prevention is fairly easy – stop gardening!

Or, you can start wearing a hazmat suit in the garden. As long as the soil can’t touch your skin, or be inhaled, you should be fine, provided you also sterilize any food you grow.

Lots of sources recommend wearing gloves to keep soil off your hands. Some suggest face masks when working with potting soil and peat moss. You should also wear closed shoes, long pants and long-sleeved shirts. These suggestions probably help, but I could find no science to confirm how effective they are. These are just things that health professionals suggest as standard practice for the prevention of any disease.

As we have now learned, a face mask does not prevent you from getting the coronavirus, so it is unlikely to prevent other soil borne diseases.

Tetanus Immunization

There is no preventative injection for most of the soil borne diseases, but tetanus is an exception. This disease has almost been eliminated in Europe and North America because of immunization programs. It does require a booster shot and traditionally this has been recommended every 10 years, although some now think that every 30 years is enough.

Natural immunity to tetanus decreases as we age, and this shot may be more important for us, older gardeners.

Reality Check

The chances of getting a soil born disease from gardening is extremely low. Unfortunately, humans have a very hard time making sense of risk data. These facts might help.

It is much more likely that you die from influenza than from any garden disease.

Driving to the garden center is thousands of times more deadly that working in the garden.

If you stay in the garden, don’t associate with other people during flu season, and stop driving, you will be much safer!

Wearing gardening gloves is probably a good idea. At the very least you end up getting fewer cuts. But since we tend to use the same gloves repeatedly, I’m not sure how clean they are. Masks are not as effective as people think they are and are probably overkill.

People with immune deficiencies, or very young people should take some extra precaution. Almost all of the soil born diseases affect them more.

If you do get ill, make sure you tell your doctor that you garden so that they can consider soil borne issues.

Next time you see a meme on social media, promoting fear about soil born diseases, post a link to this article.