Schistosomiasis Control: Leave No Age Group Behind

Abstract

Despite accelerating progress towards schistosomiasis control in sub-Saharan Africa, several age groups have been eclipsed by current treatment and monitoring strategies that mainly focus on school-aged children. As schistosomiasis poses a threat to people of all ages, unfortunate gaps exist in current treatment coverage and associated monitoring efforts, preventing subsequent health benefits to preschool-aged children as well as certain adolescents and adults. Expanding access to younger ages through the forthcoming pediatric praziquantel formulation and improving treatment coverage in older ages is essential. This should occur alongside formal inclusion of these groups in large-scale monitoring and evaluation activities. Current omission of these age groups from treatment and monitoring exacerbates health inequities and has long-term consequences for sustainable schistosomiasis control.

Keywords: adults; health inequities; mass drug administration; praziquantel; preschool-aged children; schistosomiasis.

Figure 1.. Age transitions across lifetime and treatment interventions for individuals in schistosome endemic regions in sub-Saharan Africa.

(A) Infants (<1 year) and preschool-aged children (1-4 years) are currently not included any mass drug administration (MDA). At risk adults (>14 years) are only included in MDA if the prevalence in school-aged children is >50% (see endemicity). (B) Estimates of the proportion of school aged children (here shown as 5-14 years) in Sub-Saharan African countries requiring schistosomiasis preventive chemotherapy (data from [7, 14]). Red points indicate countries that include SAC in MDA in 2017 and/or 2018, the most recent reporting years. All countries(C) Estimates of the proportion of adults (here shown as 15 years and older) in sub-Saharan African countries requiring schistosomiasis preventive chemotherapy. Red points indicate countries that give MDA to adults in 2017 and/or 2018, and white indicates no MDA programmes that include adults. Absence of points and shading indicate data not available (or outside sub-Saharan Africa).

Figure 2.. Distribution of populations and schistosomiasis burden across age groups in sub-Saharan Africa.

(A) Growing populations in sub-Saharan Africa means that the population, on average, is very young [14], the solid red rectangle indicates individuals eligible for school-based mass drug administration (MDA), whereas the dot-dash rectangle indicates those currently included in community-based MDA. (B) The majority of the population are in the adult age group (ages 15 and above). (C) Prevalence of Schistosoma mansoni across major age groups in a survey of 10,000 in Uganda (data from [15]). Peak prevalence in females occurs between 15-19 years, whereas males’ peak prevalence occurs from 20-29 years, and then falls in both sexes as they grow older. (D) Schistosoma mansoni infection intensities from the same population, showing infection intensities peak at approximately the same age (or even older for females) and then decline more rapidly than prevalence.