The results of the present study show that the Niakhar district is endemic for urinary schistosomiasis. The prevalence (57.6%) and intensity of S. haematobium infection (185 eggs/10 ml) indicate a high risk at the community level in accordance with the WHO definition . This high rate of egg excretion might be due to the age group studied because children from 7 to 14 years old are the most important egg shedders [21, 22]. In addition, only 5.5% of children had received treatment for schistosomiasis, which would explain the rates observed. This finding is also attributable to intense water contact activities in the area. The same observation was also made in Senegal (in the region of Bignona, Casamance , at Barkedji in the department of Linguere ) and in several Nigerian villages around the Gusau dam, Zamfara . Communities in the study area of Niakhar are rural, and most of the villages depend on backwater and ponds for their water needs, such as bathing, swimming, fishing and other domestic uses. These water bodies provide natural water sources and also serve as habitats to intermediate hosts (bulinids) and schistosome parasites. These water bodies constitute the main transmission foci of S. haematobium in the communities and are distributed throughout the area. These conditions make it certain that the people will continue to be infected and re-infected because no intervention strategy has been implemented in the area.
However, the differences found in the prevalence and intensity of infection between the villages investigated could be attributed to the fact that people living in Datel, Gajiak, Godel and Kothiokh were dependent on backwater as their principal water source during the rainy season. The high prevalence in these villages reflects the higher level of exposure and dependence of these inhabitants on backwater, which persists during the dry season [11, 14]. In addition, these villages did not have access to tap water . The low prevalence observed in the other villages might be due to the fact that they depended on ponds, which dried more rapidly than backwater, and to the presence of running water for their daily uses. This observation agrees with other reports conducted in Nigeria [25, 26] where variability and epidemiology of the disease were attributable to water-contact patterns. It is also similar to the observations by Nkengazong et al. , who showed in south west Cameroon that villages without pipe-borne water access maintained a high level of infection. However, in some villages with running water in the Niakhar district, the prevalence was also high. This situation might be explained by other factors such as the proximity with ponds, lack of health education and poor hygiene.
The higher prevalence in boys than in girls confirms other reports for human infection in Senegal [24, 28] and in several different localities in West African countries [29, 30]. However, this result does not agree with the reports by Dabo et al.  in Mali and Ahmed et al.  in central Sudan, who found similar prevalence in boys and girls. EGMC was strongly correlated with gender, with boys being more heavily infected than girls. This difference noted in the Niakhar district may be due to cultural, behavioral and social factors. Indeed, during the rainy season, boys participate in various activities, such as swimming, washing domestic animals, fishing, etc., that create frequent and prolonged contact with water sources. In contrast, girls are restricted socially from water contact activities such as swimming and bathing. They also go to backwater and ponds for the washing of clothes or fetching water for domestic work. In villages with running water, girls usually stay at home and generally use tap water for housework, thus reducing their contact with other water sources. Boys thus constitute a high risk group for urinary schistosomiasis in Niakhar.
The highest prevalence values of urinary schistosomiasis were recorded in the 10–12 and 13–15 year groups. These age classes are most likely responsible for schistosomiasis transmission in the area. The increase of prevalence with increasing age of children was also noted in other African countries. In Burkina Faso, Poda et al.  found a significant difference between three age groups (7–9, 10–12, and 13–16 years). A similar result was also reported by Briand et al.  in two villages from the same district of Niakhar. In the present study, the percentage of infected schoolchildren in the 10–12 year group was practically equal to that noted in the 13–15 year group, and this last finding agrees with several reports [22, 34] where there was a peak at 10–14 years. No significant difference was observed between the age of children and the intensity of infection. This finding also agrees with previous reports [34, 35] where the intensity of infection did not show any significant difference with the age of children.
If children are grouped by age and sex, the intensity of S. haematobium infection increased with age in boys but decreased in girls. According to Gryseels et al. , the decline of intensity of infection among older children in some populations is due to a decreased contact with infected water . In the Niakhar district, the decrease in infection observed among older girls might be explained by their seasonal migration to urban areas during the rainy season to seek employment as domestic workers . Boys stay in the villages during the rainy season, thus maintaining a high intensity of egg parasites, most likely due to seasonal re-infection. A snail survey is needed to assess the role of water sources in the transmission of S. haematobium. The implementation of a control program in this area to decrease prevalence and intensity would also be highly suitable.