Experimental Contamination of Vegetables with Helminth Eggs

In countries with limited water resources, the agricultural use of treated wastewater represents an interesting alternative. A recently published international report (Engelberg report 1985) shows the importance of strict parasitological criteria for such reuse. In this study we have tested the survival of Ascaris eggs on different edible crops (lettuce, radishes, chives) and in different soils (clay, sand, silt) irrigated with water artificially contaminated. Leaves and roots from vegetables, surface and deep samples from soil were analyzed. In the soil the survival of Ascaris eggs is dependent on 2 factors : exposure to sunlight and soil type. Up to 20 days the Ascaris egg survival is significant,after which time it decreases quickly. In vegetable samples 10 days after the contamination by spraying no eggs are found on leaves of any crops. In roots samples after 10 days the Ascaris recovery is dependent on type of vegetables. These differences could be explained by different radicular system. After 45 days, the decrease is similar for all the crops. These results underline the importance of parasitological criteria for the agricultural wastewater reuse.