A total of 1642 schoolchildren were enrolled in the study. The overall sex ratio (male to female) was 1.27: 1, but the sex distribution varied greatly according to the village, ranging from 14.9% to 73.3% for girls. The overall mean age was 8.7 years, without any significant difference between schools. The number in each age group was 532, 546 and 565 for the 7, 8 and 11 years old respectively.
The most commonly reported symptoms were bloody urine (41.8%), abdominal pain (28.5%) and pain when urinating (24.5%). A previous treatment against schistosomiasis was reported by 4.5% of the schoolchildren. No previous treatment had been administered at community level in any of the eight villages.
The overall prevalence of S. haematobium infection was 75.4% [95% Confidence Interval (CI): 73.2–77.5]. The prevalence varied from 43.6% to 97.7%, according to the village. Older children were more frequently infected than were younger ones (p<0.01). The overall prevalence of heavy-intensity infections was 21.8%. Intensity increased with increasing age: 16.4%, 21.8% and 27.0% in children aged 7, 8 and 11 years, respectively (p<0.01). Among the heavily infected children, 50 (13.9%) excreted more than 500 eggs/10 ml of urine. The geometric mean egg count among egg excreting children was 15.5 eggs /10 ml urine. Geometric mean egg counts were 11.7, 16.9 and 17.6 in children aged 7, 8, and 11 years respectively (p<0.01). The prevalence of infection was significantly higher in schools located in the south-western part of the country: 85.3% in the region of Tillabéry compared to 64.8% in the region of Tahoua (p<0.01). The prevalence of S. haematobium infection was significantly associated with reported haematuria and pain during urination (p<0.01).
S. mansoni infection was observed only in 2 schools: Sabon Birni (3%) and Sanguilé (1.1%).
Hookworm infection was observed in 3 schools; Sabon Birni, where the prevalence was 18.8 and in 2 other villages were the prevalence was 0.6%. Hookworm infection was not observed in the schoolchildren of the 5 other villages.
Very low prevalence (0.3 to 0.7%) of Ascaris lumbricoides infection was observed in 5 schools, while 3% of the schoolchildren were infected in 1 school (Sanguile) and no infection was observed in 2 schools (Kaou and Tabalak).
The overall prevalence of P. falciparum infection was 8% in the 636 tested schoolchildren, ranging from 3.8% to 15.8% according to the village (p<0.03). P. falciparum infection was neither associated with age, nor S. haematobium infection.
The overall prevalence of observed gross haematuria was 6.9%, with a significant relationship with S. haematobium infection (p<0.03). Gross haematuria was observed in 21.4% of heavily infected children. The overall prevalence of micro-haematuria was 53.3%, differing significantly according to the village (p<0.03) and increasing significantly with increasing age (p<0.03). The prevalence of micro-haematuria was 9.6% in children not excreting eggs, 56.3% in children with light-intensity infections and 92.8% in children with heavy-intensity infections (p<0.03). Reported history of haematuria and pain during urination were significantly associated with the prevalence of micro- and gross haematuria (p<0.03).
Overall, the mean haemoglobinemia was 11 g/dl (range: 5.3 g–17.3 g). The prevalence of anaemia was 61.6%, without significant difference between sexes. Haemoglobinemia was significantly related to age: 66.5% in children aged 7 years, 64.6% in children aged 8 years and 54.1% in those aged 11 years (p<0.03
). Prevalence of anaemia was also statistically different according to the village (p<0.03
). Anaemia was significantly associated with micro-haematuria (p
<0.02), but not to gross haematuria. Overall, we found a significant association of anaemia with S. haematobium
infection coded as a binary variable yes/no (p
0.045), but not with infection coded into 3 levels of intensity. After adjusting for age, the association was present only in 8 year old children, where prevalence of anaemia increased significantly with increasing intensity of infection (p<0.01
). The presence of anaemia was significantly associated with P. falciparum
). shows the prevalence of anaemia according to the presence, or absence, of several potential risk factors using bivariate analysis.
Prevalence (%) of anaemia according to the absence or to the presence of several potential risk factors at the baseline data collection
The proportion of children presenting at least one ultrasound abnormality of the urinary tract was 45.8%, without significant differences between sexes or transmission patterns, and was significantly associated with age (37.8%, 46.0% and 53.0% in children aged 7, 8 and 11 years, respectively; p<0.03
), to the intensity of S. haematobium
infection (22.1% in children not excreting eggs, 47.5% in light-intensity infections and 68.1% in heavy-intensity infections; p<0.03
) and to the presence of anaemia (p
Bladder wall abnormalities, evident in 41.6% of children, were the most frequently reported ultrasound abnormality. Their prevalence increased significantly with increasing age (p<0.03), with increasing intensity of infection (p<0.03), and was not associated with the presence of anaemia. Severe bladder wall abnormalities (either masses or pseudopolyps) were present in 15.5% of the children. Kidney and ureteral distensions were present in 4.2% and 4.1% of the children, respectively. Contrary to ureteral distension, kidney distension was significantly associated with the intensity of S. haematobium infection (p<0.01) and to the presence of anaemia (p<0.03).
The mean ESI, summarizing urinary tract morbidity due to S. haematobium infection, was 1.33 (range: 0–24) and the mean bladder score was 0.8 (range: 0–7). The mean ESI was not different between boys and girls. The mean ESI was significantly higher in pond-related transmission villages than in river-related transmission villages (p<0.03).
Multivariate analysis using logistic regression showed that the risk of anaemia was significantly associated with young age (OR
1.7, 95% CI 1.3–2.2 for age
7 and OR
1.6, 95% CI 1.2–2.0 for age
8), to the presence of ultrasound abnormalities of the kidneys (OR
3.0, 95% CI 1.5–6.0) and to the village. When the same analysis was performed on the sub-sample of 4 villages where P. falciparum
infection was documented, the predictors of anaemia were P. falciparum
2.5, 95% CI 1.3–4.7), ultrasound abnormalities of the kidneys (OR
2.9, 95% CI 1.2–6.8) and the village (OR
0.6, 95% CI 0.4–0.9 for Tabalak and OR
0.4, 95% CI 0.3–0.7 for Kaou).
A total of 89% of the initial sample group were re-examined one year after baseline data collection and the first round of treatment with praziquantel and albendazole. The mean age was 9.7 years and the sex ratio (male to female) was 1.27:1. A total of 482 eight year olds, 470 nine year olds and 484 twelve year olds were re-examined.
The overall prevalence of S. haematobium infection was 38% and 4.6% of children had heavy-intensity infections; only three (4.6%) among the latter excreted more than 500 eggs/10 ml. 56.2% of the initially infected children did not excrete eggs and 91.6% of heavy-intensity infections had cleared or become light intensity infection. However, the improvement of infection markers was different according to the village and prevalence was still above 60% in 3 schools (Kaou, Kokorou and Tabalak). In children from Tabalak, only minor changes in the prevalence and intensity of infection were observed (22.7% of heavy-intensity infections at baseline and 18.2% at follow-up).
Assessment of P. falciparum infection in the 4 schools tested in 2005 showed a significant increase of the prevalence from 8.6% to 17.1% (p<0.03). The rise of prevalence of malarial infection was observed in 4 schools, although only statistically significant in Rouafi (paired analysis, p<0.03).
The overall prevalence of all the morbidity markers of S. haematobium had decreased significantly at follow-up (). Among the 1412 schoolchildren which were re-examined, the overall prevalence of anaemia decreased from 61.9% to 50.4% (paired analysis, p<0.03) and the mean haemoglobinemia showed a significant increase of 0.39 g /dl to reach 11.4 g/dl (paired analysis, p<0.01). However, the change in prevalence of anaemia was not significant in children from Kaou, Kokorou, Mozague and Tabalak. At follow-up, anaemia was not associated with S. haematobium infection. Gross and micro-haematuria decreased from 7.1% to 0.4% (paired analysis, p<0.03) and from 53.5% to 6.0% (paired analysis, p<0.03), respectively. Prevalence of gross and micro-haematuria were each significantly associated with the intensity of S. haematobium infection (p<0.03). Anaemia was neither associated with micro-haematuria nor with gross haematuria. One year after treatment, the overall prevalence of ultrasound abnormalities of the urinary tract and the prevalence of ultrasound abnormalities of the bladder decreased from 45.6% to 15.2% (paired analysis, p<0.03) and from 41.6% to 14.7% (paired analysis, p<0.03), respectively. The mean global ESI showed a significant decrease of 1.04 (paired analysis, p<0.03).
Evolution of the prevalence (%) of the main morbidity indicators between initial survey and re-assessment one year later (paired analysis)
In 2006, the relationship between anaemia and P. falciparum infection was no longer observed.
Compared to those children who remained in the study cohort, the 216 children who dropped out after the initial survey differed significantly in the prevalence of S. haematobium infection (75.4% vs. 78%, respectively), but had less frequently heavy-intensity infections (22.8% vs. 16.5%, respectively). On the other hand, they did not differ in mean age (8.7 vs. 8.9 years, respectively), in the prevalence of anaemia (61.9% vs. 59.7%, respectively) nor in mean haemoglobinemia (11.04 g/dl vs. 11.03 g/dl, respectively).