Assessment of the health hazards associated with wastewater reuse: transmission of geohelminthic infections (Marrakech, Morocco).

To address the problem of water scarcity, wastewater has long been used for agricultural purposes in Marrakech (Morocco) and its benefits have long been recognized. However, the benefits of urban wastewater reuse may be limited by its potential health hazards associated essentially to the danger of transmission of pathogenic organisms to human beings. The current study aimed to evaluate the risks associated with raw wastewater reuse for agricultural purposes, and the incidence of geohelminthic infections among the children of the wastewater spreading area of Marrakech as compared to a control group. Faecal samples from 610 individuals were examined for Ascaris spp. ova and Trichuris spp. ova (323 children for the exposed group and 287 for the control group). The study duration was two months and a half, and was carried out in the summer period. A questionnaire-interview with children and parents was used to collect data on possible demographic, hygiene and behavioural-contact factors such as gender, age, family size, source of water supply, parental occupation. The investigations resulted in the detection of Ascaris spp. ova in 43 samples indicating a point-prevalence of 13.3% in the exposed group versus 1.7% for the control group. Trichuris spp. ova was detected in 43 faecal samples indicating a point-prevalence of 13.3% in the exposed group, and 3.8% in the control group. The Chi-square test showed that the differences observed between the exposed and control group are statistically significant (p < 0.01). Males are more infected with ascariasis and trichuriasis than females and children of 2-8 years of age are heavily infected as compared to 9 - 14-year-old children. Based upon the findings of this study, it is concluded that wastewater reuse for agricultural purposes presents an increased risk of infection in the exposed group.

Health effect of human wastes use in agriculture in El Azzouzia (the wastewater spreading area of Marrakesh city, Morocco).

The use of wastewater and excreta in agriculture constitutes an important source of spread Salmonella strains and protozoan infections into the environment. This practice has been used in El Azzouzia (the wastewater-spreading area of Marrakesh city, Morocco) for several years. The available circumstantial evidence gained from epidemiological and microbiological investigations suggests that the use of untreated wastewater causes an excess of protozoan infections among children living in El Azzouzia (72%) compared with those from a control area (45%). The pathogenic protozoan infections observed were giardiasis (39%) and amoebiasis (28%). For Salmonella infection, 21.34% of the exposed children were infected, while this rate did not exceed 1.14% in the control group. The serogroups B and C were the most commonly isolated. The sewage farming children are therefore more exposed to detectable risk from pathogenic micro-organisms than the control children.

Health effect of wastewater reuse in agriculture.

The present study addresses the impact of wastewater reuse in agriculture on the transmission of protozoan and helminthic infections. For this purpose, an epidemiological study was carried out on two populations of children totalling 608 individuals for protozoan infections and 528 for helminthic infections. Each population comprised an exposed group living in the wastewater spreading area of Marrakech and a control group. Results showed that 72% of the exposed group had protozoan infections. This rate did not exceed 45% in the control group. The pathogenic protozoan infections observed were giardiasis and amoebiasis. Regarding helminthic infections, 73% of the exposed children were infected compared with 30% of the control group. The risk attributable to wastewater reuse in the transmission of pathogenic protozoan and helminthic infections was 41% and 43%, respectively. Children of the spreading area are therefore more exposed to detectable risks from parasitic helminths and protozoa than the control children.

The effect of waste water reuse in irrigation on the contamination level of food crops by Giardia cysts and Ascaris eggs.

In Marrakech, raw sewage has been used for farming purposes for several decades for many types of crops. This study aimed to determine the contamination level of Giardia cysts and Ascaris eggs for crops designated for human consumption. Collected crops in irrigated fields were turnip, marrow, squash, potatoes, pepper and eggplant. Field trials were also carried out on four crops, coriander, carrots, mint and radish, using three water types for irrigation, i.e. raw waste water, treated waste water (sedimentation and 16 days retention) and fresh water. Giardia cysts were detected at a level of 5.1 cysts/kg in potatoes, while Ascaris eggs were observed in numbers varying between 0.18 eggs/kg in potatoes and 0.27 eggs/kg in turnip. Field trials confirmed that irrigation of crops by raw waste water leads to contamination. Giardia and Ascaris were isolated in coriander at concentrations of 254 cysts/kg and 2.7 eggs/kg, respectively; mint was also highly contaminated with numbers reaching 96 cysts/kg and 4.63 eggs/kg. Carrots and radish were contaminated and respective numbers observed for Giardia were 155 and 59.1 cysts/kg; Ascaris was discovered in numbers of 0.7 and 1.64 eggs/kg, respectively. However, cultures irrigated with treated waste water and fresh water were free from contamination. Cysts and eggs on coriander persisted for a maximum of 8 days.

Epidemiological study of intestinal helminthiasis in a Marrakech raw sewage spreading zone.

It has been suspected for some time that raw sewage is a potential source of protozoan and helminthic infections (10). Shuval et al. (16, 17) and W.H.O. (21) have shown that irrigating crops with untreated wastewater causes significant intestinal infections in both consumers and farm workers. This study compared the stools of "sewage farming" children exposed to raw sewage (El Azzouzia area) and those of a control group. Stool specimens from 253 exposed children and 275 controls were analyzed. 73% of the exposed were infected with one or more helminths verses 30% of the control group. The main parasites were Ascaris and Trichuris. The El Azzouzia children were more heavily infected and their polyparasitism index (PPI: 13%) was considerably higher than that of the controls (PPI: 2%). Thus "sewage farming" children are exposed to detectable risk from the parasitic nematodes in raw sewage.

Quantification of helminth eggs in waste water.

Agricultural use of waste water has been regulated mostly by its bacteriological quality. Recently the importance of parasitological criteria for waste water standards was recognized by establishing that waste water containing less than 1 intestinal Nematode egg per liter is released for unrestricted use of effluents. At present, most of the techniques borrowed from parasitological coprology are only qualitative. In this report different protocols for helminth egg quantitation were compared. Three flotation techniques (Janeckso-Urbanyi, Faust, Arther) and two sedimentation techniques (Bailenger, Ritchie) and their performances were evaluated. Although all the techniques were based on the same number of on the whole positive samples, significant differences were observed in both the number of species identified and in the type of egg preferentially concentrated. Among the flotation methods tested, the Janeckso-Urbanyi modality offers undeniable advantages in efficiency and in the variety of species concentrated, but it is relatively costly. Among the sedimentation techniques, the one described by Bailenger is relatively inexpensive and concentrates all the types of eggs normally found in waste water samples, except for the relatively rare Enterobius with globally satisfactory yields.