Pathogenic parasites in sewage irrigated crops and soil: pattern of occurrence and health implications

The current study aimed to determine the contamination level by human parasite eggs and cysts of sewage-irrigated soil, food crops and fodder crops. Field trials were conducted on spray-irrigated lettuce and flood-irrigated crops using raw wastewater and fresh water. Findings showed that irrigation by raw wastewater led to crops contamination with parasite eggs and cysts in varying levels. Lettuce samples were positive (27.7%) for one or more helminth eggs including the pathogens Ascaris and Trichuris with an average of 4.7 eggs/kg. Wastewater application caused an increase in lettuce contamination, followed by a decreasing phase. Cessation of irrigation resulted in helminth eggs disappearance within a week. Flood-irrigated crops were contaminated with helminth eggs in levels ranging from 1.5 eggs/kg in alfalfa to 4.75 eggs/kg in coriander. The pathogenic Giardia,Entamoeba histolytica/dispar and commensal amoeba cysts were highly detected reaching 9.97x10³ cysts/kg in alfalfa. Parasites highly concentrated in soil, with levels up to 159 eggs/100gdw and 1.3x10³ cysts/gdw. Ascaris and Trichuris eggs developed in soil and crops attaining the infective stage. Crops and soil irrigated with fresh water were free from parasite eggs and cysts. The occurrence of pathogens in soil and crops implies health risks for farmers, produce handlers and consumers.