The Viability of E. Histolytica Cysts in Soil

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Irrigation with polluted water, use of nightsoil, pollution by flooding, or direct deposition of human feces may carry cysts of E. histolytica onto vegetable gardens and truck farms. Seepage and tilling of the soil would tend to separate the cysts from the fecal mass and distribute a portion of them below the surface where they would be protected against direct sunlight, high temperature, and desiccation. Under these conditions, providing the soil itself is not a hostile environment, cysts might remain viable for relatively long periods, be transported to the markets, and thus become a potential source of infection. It has been assumed that this does occur. Craig (1) states that uncooked vegetables from gardens fertilized with nightsoil are a very common source of infection in those countries where the practice prevails; and Andrews' study (2) of an unsanitated mining community in Mexico indicated that the high incidence of amebic infection found there probably was due to the use of raw sewage for irrigating the vegetable gardens.

Author Notes

For general arrangements and provisions for our investigations we are indebted to Dr. Alfred Gage, Medical Director, Standard Oil Company. Also we wish to acknowledge the assistance of Dr. Rafael Risquez, Dr. A. La Corte, Prof. Charles Sous, Mr. O. J. Ayala, and other members of the Medical Department of the Creole Petroleum Corporation in Caracas and Caripito, Venezuela.