A 12-year follow-up of intestinal schistosomiasis in pre-school-aged children in Assoni Village, Eastern Senegal

Abstract

Background: To monitor the prevalence of schistosomiasis in school-aged children (SAC), the National Bilharzia Control Program (PNLB) was set up by the Senegalese authorities; however, geographically isolated Bedik ethnic groups that did not benefit from this program were found to be heavily infected with Schistosoma mansoni. This observation led us to implement a new schistosomiasis control program in 2008 under the aegis of the non-governmental organization "Le Kaïcedrat" and in partnership with the PNLB/WHO to monitor the prevalence of schistosomiasis in this area. In the village of Assoni, where 100% of SAC were infected, analysis of the stools of pre-school-aged children (PSAC) showed that they were massively infected, so we decided to focus our program on them.

Methods: From 2008 to 2020, we (i) monitored the prevalence of S. mansoni in PSAC in Assoni using double-stool smear preparation, (ii) treated the infected PSAC with a standard dose of praziquantel 40 mg/kg, (iii) ran educational campaigns each year in the village, and (iv) built latrines to improve sanitation and reduce schistosomiasis transmission. Linear regression was used to examine the trend in the annual schistosomiasis prevalence and a two-sided of Chi-squared test was used to compare prevalence between the different age groups of PSAC.

Results: We observed an extremely high prevalence of schistosomiasis (78%) in PSAC before implementation of the program in 2008. Contamination occurred in very young children, as 64.3% of children under 2 years old were infected. Moreover, prevalence increased with age and reached 96.8% in children 4 to < 6 years old. Our annual interventions in Assoni Village raised awareness among villagers that water bodies were areas of significant infestation, allowed the building of 88 latrines and led to a decrease in prevalence in PSAC as only 11% of these children were infected in 2020.

Conclusion: Our study allowed Assoni to be the first village in Senegal to treat PSAC since 2014, but only on an individual basis. It also shows that schistosomiasis is difficult to eradicate and that multi-sectorial actions are required to keep its prevalence at a low level.

Keywords: Intestinal schistosomiasis; Latrine; Praziquantel; Pre-school-aged children; Prevalence; Senegal.

Fig. 1

Location and topography of Assoni village. A Location of Assoni village in Kedougou district. B Location of Assoni Village and Bediks territories. C Assoni village is accessible by only one track which is often difficult to access (white line). It is crossed by a watercourse that turns into water bodies during the dry season (orange line). A concrete footbridge was built to allow children to go to school (former school) without crossing the backwater. However, the school was damaged and was rebuilt (new school). The many paths that join the different parts of the village and cross the infested water bodies are depicted by red arrows

Fig. 2

Schedule of prevalence monitoring and treatment of PSAC and SAC in Assoni village. Regarding SAC, MDA was realized in 2008 and Schistosoma mansoni prevalence was assessed each year in 1/3 of SAC. From 2009 to 2013, all the children entering their sixth year were treated systematically, as well as SAC who were found to be infected after prevalence monitoring. Since the closure of Ninefesha Hospital in 2013, PNLB has begun to treat SAC attending school. Non-attending school children who were found to be infected after our prevalence assessment were treated on an individual basis. In blue, prevalence assessment or treatment performed by our program; in green treatment performed by PNLB. MDA: Mass drug administration; PNLB: Programme National de Lutte contre la Bilharziose; PSAC: Pre-school-aged children, SAC: School-aged children

Fig. 3

Prevalence of Schistosoma mansoni among different age groups of pre-school-aged children (PSAC) in Assoni. Prevalence in PSAC was assessed at 0 to < 2, 2 to < 4 and 4 to < 6 years of age from 2008 to 2020. Prevalence was not assessed in 2009, 2010 and 2012 because mothers did not want their children to be sampled as they could not benefit from any treatment

Fig. 4

Comparison between prevalence of Schistosoma mansoni among pre-school-aged children (PSAC) and school-aged children (SAC) in Assoni. Schistosoma mansoni prevalence was assessed in Assoni from 2006 to 2020 in PSAC and SAC. na: no available data