[Intestinal parasitosis in the inhabitants of a suburban zone in which the groundwater is polluted by nitrates of fecal origin (Yeumbeul, Senegal)]. / Les parasitoses intestinales chez des habitants d'une zone péri-urbaine à nappe phréatique polluée par les nitrates d'origine fécale (Yeumbeul, Sénégal)

This study was carried out in 1997 to 1998, to determine the prevalence of intestinal parasite infestations due to groundwater pollution at Yeumbeul, Senegal, and to follow the progression of parasite infestations following anti-parasite treatment. The study included 705 people living in a suburban zone in which the water table was polluted with nitrates of fecal origin. These individuals consumed either well water or water from springs. The overall prevalence of parasite infestation was 42.26%, but varied significantly with age (p < 0.001). Individuals who consumed well water were more frequently infested than those who consumed spring water, but the difference was not significant (p > 0.3). Giardia and Entamoeba coli were the most frequently isolated parasites, with Giardia predominating in the 0 to 9 year age-group. There was no significant correlation between the prevalence of the various parasites and indicators of water pollution (R2 = 0.0566 for nitrates and 0.1086 for fecal coliform bacteria). Similarly, no correlation was found with water pollution factors such as the depth of the water table (R2 = 0.027) and the distance between the wells and the latrines (R2 = 0.00007). Following specific treatment, the prevalence of parasite infestation fell to 30.81%. This indicates the limitations of drug treatment, which is always used alone to combat intestinal parasites, in the face of possible reinfestation.

Nitrate pollution study in the aquifer of Dakar (Senegal).

Dakar is a peninsula inhabited by a population of about 2 million people in 1996. In some dug wells and piezometers, the nitrate content (NO3.) in the groundwater is above the World Health Organization (WHO) limit of 50 mg/l. In the unconfined part of the aquifer of the peninsula, all the samples from wells are contaminated by high nitrate contents which increased over time from 100 mg/l in 1987 to more than 250 mg/l in 1996. Only a limited area is affected by nitrate pollution in the confined layer. The results indicate anthropogenic pollution, a fact which indicates the increasing risk of pollution of drinking-water resources. Studies in the unsaturated zone and familiarity with the sanitation practices in the area indicate that the horizontal and vertical flux are linked mainly to defective septic tanks and direct organic waste elimination into the soil by more than 40% of the inhabitants. The correlation between tritium values (3H) and nitrate shows that the source of nitrate is recent. The relation of oxygen 18 (18O) to deuterium (2H) in water with high nitrate levels indicates that the concentrations of nitrate have been identified in evaporated points.