Soils are a remarkable home for an array of biodiversity with approximately 25% of the Earth’s species making their home in the soil. A majority of organisms living within the soil are not of any threat to human health, but rather function to provide numerous ecosystem services which emerge through the multitude of complex interactions between organisms within the soil and the soil itself.
Soil is vital to human existence and the vast majority of organisms that reside in it function to our benefit. However, soil also harbors a minority of organisms – some of which call soil their home, while others pass through it transiently – that are capable of causing diseases in humans: these are soil-borne human pathogens and parasites.
These complex ecosystem services range from those which are vital for maintaining life on Earth, such as the formation of soil, the cycling of nutrients with the result of maintaining soil fertility, and the filtering of water, as well as provision of useful compounds such as antibiotics, the majority of which have been isolated from soil organisms.
Unfortunately, soils are also home to microorganisms which are capable of causing diseases in humans as seen in recent events of Salmonella and E. Coli contamination in much of the country’s spinach and lettuce which was recalled after infecting many individuals. Exposure to infectious organisms from the soil has been known for centuries. Some microorganisms are opportunistic pathogens which take advantage of susceptible individuals, such as those who are immuno-compromised; or as obligate pathogens which must infect humans in order to complete their life-cycles. These organisms may be capable of surviving within the soil for extended periods of time before infecting humans who come into contact with contaminated soil.
The table below lists many of the human diseases so far identified which fall under the definition of being soil borne diseases. The pathogens responsible for causing such diseases can be divided into two groups: Euedaphic (from the Greek for ‘true soil’) pathogenic organisms (EPOs), being potential pathogens which are true soil organisms, i.e. their usual habitat is the soil. This list includes most of the bacterial pathogens and all of the fungal pathogens. The other group consists of soil transmitted pathogens (STPs). These are organisms which, while they may be able to survive in soil for extended periods of time, are not true soil organisms, but rather are obligate pathogens who must infect a host in order to complete their life cycles.
Common vegetables such as lettuce and spinach which were recently infected by E. Coli and Salmonella can easily be grown hydroponically eliminating the need for soil and avoiding numerous soil borne diseases. A closed hydroponic systems will also greatly conserve water and avoid fertilizer run off further protecting the environment.