Prevalence of Schistosoma infection
Table 1 summarises the prevalence of Schistosoma infection, stratified by sex, age group and school. Schistosome eggs were detected in the stool and urine of 33 of the 274 children surveyed (12.0%) in October 2016. The prevalence of S. mansoni and S. haematobium were 9.5% and 2.6%, respectively. None of the children were concurrently infected with both S. mansoni and S. haematobium. From the initial 75 SCORE schools, six were included in the present study. In Gbadrou, Mona, Ziondrou and Zoukougbeu, S. mansoni prevalence failed to decrease by at least 35% and/or the intensity of infection failed to decrease by at least 50% when comparing the baseline situation in 2012 with the endline situation in 2016 after multiple rounds of treatment (Table 2). Hence, these four schools were considered PHS in the present analysis. The remaining two schools (Tobly Bangolo and Zê) achieved a S. mansoni prevalence reduction by at least 35% and/or the intensity of infection declined by at least 50%. Subsequently, these two villages were considered low-prevalence schools. In general, prevalence and intensity of S. mansoni infection decreased meaningfully in schools where children received four rounds of praziquantel treatment compared with schools where only two treatments were performed.
The average S. mansoni prevalence in the four PHS was 10.9% (95% CI: 6.8–16.4%), while it was 6.6% (95% CI: 2.5–13.8%) in the two low-prevalence schools. The highest S. mansoni infection prevalence was found in Ziondrou (22.7%, 95% CI: 11.5–37.8%). The arithmetic mean egg count among S. mansoni-positive individuals was 123.8 epg in the four PHS schools and 18.7 epg in the two low-prevalence schools. Schistosoma mansoni prevalence was significantly different between schools (χ2 = 14.3, df = 5, P = 0.014). Infections with S. mansoni were mainly light (80.8%), while moderate (15.4%) and heavy (3.9%) infections were less common. The two age groups did not differ significantly in the S. mansoni prevalence (χ2 = 0.1, df = 1, P = 0.751).
The average S. haematobium prevalence was 3.3% (95% CI: 1.2–7.0%) in the four PHS schools and 1.1% (95% CI: 0.03–6.0%) in the two low-prevalence schools. The highest prevalence of S. haematobium was found in Zoukougbeu (8.2%, 95% CI: 0.2–16.1%). Among S. haematobium-positive children in the four PHS schools, the intensity of the infection was 16.7 eggs/10 ml of urine (95% CI: 0.3–33.0 eggs/10 ml of urine). All S. haematobium infections were of light intensity (< 50 eggs/10 ml of urine). Schistosoma haematobium prevalence differed significantly between the two age groups with children aged 11–12 years at higher odds of infection (χ2 = 11.0, df = 1, P = 0.001).
Table 3 summarises the demographic characteristics of the study villages, including results from the questionnaire survey regarding the last round of preventive chemotherapy. Overall, 299 children participated in the parasitological survey. However, 25 children were absent during the questionnaire survey, resulting in 274 children with complete parasitological and questionnaire data. There were 150 (54.7%) boys. There was no significant sex difference between the two groups of schools. With regard to age, 60.6% of the children were in the younger age group (9–10 years) with no significant difference in the age groups between the PHS and low-prevalence schools (P = 0.805) (Table 4).
Most of the children (97.5%) declared that they were present during the last treatment round and 95.3% of them had received praziquantel. Reasons for not taking the drugs were absence for at least five days (37.5%), unwillingness to be treated based on a dose pole (25.0%), feeling healthy (12.5%), feeling too sick (12.5%) or absence of a community health worker during treatment administration (12.5%). There was no statistically significant difference between PHS and low-prevalence schools in terms of praziquantel coverage (P = 0.055). In Ziondrou and Zoukougbeu, all the surveyed children reported having received the drugs, while in the remaining schools some children were missed out. Two-thirds of the children (65.7%) said that they did not know which disease praziquantel cured. About one out of seven children (13.5%) was of the opinion that praziquantel cured stomach diseases. Slightly more than 10% of the children reported that praziquantel cured worms (10.6%) or other non-specified diseases (10.2%). There was no association between children’s knowledge and the prevalence of S. mansoni (χ2 = 0.9, df = 3, P = 0.818). There was no significant difference between PHS and low-prevalence schools in the proportion of children who reported that praziquantel cured worm disease or stomach ache (P = 0.714).
Socioeconomic status and WASH indicators
Figure 1 shows the characteristics of household materials in the study villages. Most of the children in Zoukougbeu lived in houses with walls made of bricks, stones or cement (91.8%) and floors made with cement, tiles or linoleum (93.9%). The majority of children’s families had houses covered by metal roofs (91.8%). In Mona, houses were predominantly constructed with simple or natural materials for walls (52.2%) and roofs (63.0%). Three-quarters of children’s families in the study villages had electricity at home. In Tobly Bangolo, only half of the participants had access to the power grid. Mobile phones were available in the households of all children surveyed in Zoukougbeu and Zê. Electricity at home was significantly associated with households that had at least one mobile phone (χ2 = 25.6, df = 1, P < 0.001), walls made of bricks, stones or cement (χ2 = 10.4, df = 1, P = 0.001), floors made with cement, tiles or linoleum (χ2 = 5.2, df = 1, P = 0.023) and roofs made of iron sheets (χ2 = 13.3, df = 1, P < 0.001). We found a statistically significant association between households possessing at least one mobile phone and households with walls made of bricks, stones or cement (χ2 = 7.9, df = 1, P = 0.005) and roofs made of cement, tiles or linoleum (χ2 = 13.7, df = 1, P < 0.001). The odds of being infected with S. mansoni was higher in households with floors made with cement, tiles or linoleum compared with households having other types of floors (OR: 3.55, 95% CI: 0.56–22.60) (Table 5).
Table 6 summarises WASH indicators in the study area. There were three types of public water sources: wells, pumps and taps. In PHS schools, between 30 and 38 children per school (65.2–86.4%) mentioned that their parents collected water from safe water sources for drinking or cooking. The proportions of children who reported that their parents obtained water from safe water sources were 86.4%, 72.7%, 65.3% and 65.2% in Gbadrou, Ziondrou, Zoukougbeu and Mona, respectively. In Ziondrou (65.9%) and Gbadrou (52.3%) safe water was predominantly collected from taps. In Zoukougbeu (30.6%) and Mona (28.3%), wells were the most common source of water collection for domestic use.
In low-prevalence schools, the number of children who reported that they used safe water sources was 37 (82.2%) and 33 (71.7%) in Zê and Tobly Bangolo, respectively. In Zê, water was mainly collected from taps (42.2%), while in Tobly Bangolo, wells were the predominant source (39.1%). The proportion of children who said that their parents collected water from safe sources was 72.1% in PHS schools and 76.9% in low-prevalence schools with no statistically significant difference (χ2 = 0.72, df = 1, P = 0.396). There was a statistically significant difference between PHS and low-prevalence schools in the proportion of children who reported receiving water for drinking (P = 0.005) with a higher proportion of children receiving water for drinking in low-prevalence schools.
Three-quarters of the children (74.1%) had latrines at home. Slightly less than half of the children (48.9%) had no latrine at school. In PHS, latrines were available in more than 80% of children’s houses. A high coverage of latrines at school was mainly recorded in Ziondrou (81.8%). In the low-prevalence school Zê, a high coverage of latrines both at home (80.0%) and at school (91.1%) was reported. The logistic regression analysis showed that the odds of being infected with S. mansoni was significantly lower among children from households with a latrine compared with household without a latrine (OR: 0.26, 95% CI: 0.11–0.63).
Figure 2 shows latrine availability and open defecation practice, stratified by village. Open defecation was practiced in each of the six villages studied in greater depth. In general, open defecation was less practiced in villages with a high number of latrines. In PHS, less than half of the children (43.2%) from Gbadrou claimed that they never used a latrine. Most of the children in Gbadrou (95.5%) and Zoukougbeu (65.3%) did not use latrines at school. Open defecation was widely practiced in Gbadrou (90.9%). There was no significant difference between PHS and low-prevalence schools in the proportion of children practicing open defecation (P = 0.893).
In low-prevalence schools, the number of children who had latrines (n = 36) and those practicing open defecation (n = 35) were similar in Tobly Bangolo. Most of the children (80.4%) in the later school did not use a latrine at school while defecating at school. Open defecation was commonly practiced in Tobly Bangolo (76.1%).
Table 7 summarises the water sources for playing, laundry, bathing and collecting water for domestic or agricultural use in the study area. Most of the children (61.7%) reported that they performed the aforementioned activities in lake, pond or stream water.
According to the questionnaire survey, only 7.7% of the responders played in backwater, while in Zê most of the children (97.8%) played in this type of water. More than 60% of the children did not play in rivers, while more than half of the children did so in Zoukougbeu (79.6%) and Gbadrou (52.3%) in the PHS, and in the low-prevalence school Zê (68.9%).
Most of the children did not wash laundry in lakes or small dams, with the exception of children from Zoukougbeu. Most of the responders did not wash laundry in a river, while the majority of children did so in Gbadrou (61.4%), Mona (69.6%) and Zê (71.1%). Only 25.2% of the children bathed in the river, but in Zê, half of the children did so (50.0%).
Significant differences between the four PHS and the two low-prevalence schools were found for washing the laundry, playing, bathing and collecting water for domestic or agriculture use, playing in small dams, playing in the river, washing the laundry in small dams, bathing in backwater, collecting water from the backwater, collecting stagnant water for domestic or agricultural use and using stagnant water for bathing (P < 0.05). Statistically significant differences were not found for playing and washing laundry in pond (P = 0.059). In addition, there were no significant differences for the remaining variables of water-related activities between the four PHS and the two low-prevalence schools.
Children bathing in stagnant water were at higher odds of S. mansoni infection compared with children not reporting this activity (OR: 3.67, 95% CI: 1.02–13.18) (Table 3). Children from PHS schools bathed in stagnant water more frequently compared to those from low-prevalence schools (χ2 = 5.1, df = 1, P = 0.024).
Results from the malacological survey
Table 8 summarises the results of a cross-sectional malacological survey carried out in the study area. Overall, 76 human-water contact sites were reported in the six villages. In PHS schools, the number of human-water contact sites ranged between 10 (Mona) and 19 (Gbadrou). In the two low-prevalence schools, 14 and 9 human-water contact sites were visited in Zê and Tobly Bangolo, respectively. Rivers were the most common human-water contact sites (n = 59). Rice paddies constituted another 20 human-water contact sites. There were 41 easily accessible human-water contact sites. Water is present throughout the year in all the visited sites. Among the surveyed human-water contact sites, 100% open canopy and 100% covered canopy were reported in 45 and 12 sites, respectively. Vegetation was found in 74 sites. The predominant substrata were mud, sand and roots, observed in 76, 70 and 69 of the sites, respectively. Domestic animals were found in 31 human-water contact sites, including pigs (31.3%), dogs (26.6%), cows (15.6%), chickens (10.9%), sheep (9.4%) and goats (6.3%). Birds were the only wild animals observed in all the surveyed human-water contact sites. The average pH was 6.2 (range: 5.0–7.1). The average total dissolved solids was 9.5 ppm (range: 4–51 ppm) and the average conductivity was 38.9 µS (range: 9–103 µS).
A total of 688 snails belonging to nine genera were found, namely, Biomphalaria, Bulinus, Ferrissia, Gyraulus, Lanistes, Lymnaea, Melanoïdes, Pila and Physa. Melanoïdes tuberculata (400 specimens) was the most abundant snail species. With regard to potential schistosomiasis intermediate host snails, there were 92, 25, 16 and one specimens of Bi. pfeifferi, Bulinus forskalii, Bu. globosus and Bu. truncatus, respectively. However, none of the snails were shedding schistosome cercariae, while some snails were observed shedding xiphidiocercariae.