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Many protozoan parasites have a hardy stage that survives for long periods in soil and water. Others normally thrive and multiply in the environment.
Most people have heard the common wisdom that you can catch worms from eating dirt—it’s true that a number of parasitic worms infect humans through accidental ingestion of contaminated soil—but these are not the only parasites that may be present. Protozoan parasites, tiny single celled organisms, can remain infective for long periods in soil. How do Protozoan Parasites Get Into Soil?Intestinal protozoan parasites are passed in feces. When an infected human or animal defecates on the ground, millions of parasites contaminate soil. Many protozoan parasites have a tough cyst stage—a stage that isn’t actively growing or multiplying, but which can survive and remain infective in the environment until it can infect a new host. A few of the protozoan parasites that infect humans are actually environmental species—species that normally live in soil or water and only accidentally cause disease. People Eat a Lot of DirtWe don’t think we’re eating dirt but, actually, we all eat more than we realize. Not only do we often put dirty fingers and objects in our mouths (children are particularly likely to do this), but we eat particles of dirt on raw fruit and vegetables. Tiny protozoan cysts, 5 to 100 one-thousandths of a millimetre wide, are invisible to us—there might be hundreds of them on one dirty finger. While many protozoans are better known for spreading via dirty water, human excrement is sometimes used as fertilizer, and dirty water is used to water crops—soil can certainly be a source of infection. Protozoan Parasites in DirtThe parasitic protozoa that spread through soil and water are divided up into groups—amoebae, flagellates, ciliates, and coccidia:
Avoid Protozoan Parasites in DirtIt’s impossible to completely protect yourself from microscopic intestinal parasites, but you can lessen your chances of ingesting them:
Sources:Diagnostic Medical Parasitology 3rd Ed. Garcia, Lynn S. and David A. Bruckner. Washington: ASM Press, 1997. Foundations of Parasitology 6th Ed. Roberts, Larry S. and John Janovy Jr. Boston: McGraw Hill, 2000. Related Content:
The copyright of the article Protozoan Parasites in Dirt in Human Infections is owned by Rosemary Drisdelle. Permission to republish Protozoan Parasites in Dirt in print or online must be granted by the author in writing.
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