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. 2021 Mar 8;104(5):1841-1850.
doi: 10.4269/ajtmh.20-1433.

Five-Year Follow-Up on the Prevalence and Intensity of Infections of Schistosoma mansoni in a Hard-to-Reach District of Madagascar

Stephen A Spencer  1   2 , Cortland Linder  2 , James M StJ Penney  2 , Hannah J Russell  2 , Kate Hyde  2 , Caitlin Sheehy  2 , Alice Reid  3 , Emmanuel H Andriamasy  4   5 , Gina U Raderalazasoa  5 , Daniel A L Rakotomampianina  5 , Anjara M Nandimbiniaina  5 , Tahiry N Ranaivoson  5 , Antsa Andrianiaina  5 , Sheena M Cruickshank  5 , Amaya L Bustinduy  6 , J Russell Stothard  3 , Glenn T Edosoa  7   8 , Alain M Rahetilahy  8 ; MADEX
Affiliations

Five-Year Follow-Up on the Prevalence and Intensity of Infections of Schistosoma mansoni in a Hard-to-Reach District of Madagascar

Stephen A Spencer et al. Am J Trop Med Hyg. .

Abstract

Schistosomiasis is a major public health problem in Madagascar. The WHO recommends preventive chemotherapy by mass drug administration (MDA) with praziquantel as the primary approach to control Schistosoma mansoni-related morbidity in endemic populations, alongside complementary interventions such as health education. The impact of annual MDA and health education programs was assessed in the hard-to-reach Marolambo district of eastern Madagascar, an area endemic for S. mansoni. Repeated cross-sectional studies undertaken 2015-2019 examined between 300 and 381 school-aged children (aged 5-14 years) annually. The prevalence and infection intensity of S. mansoni were assessed by urine-circulating cathodic antigen (CCA) dipsticks and coproscopy using Kato-Katz (KK) methodologies. After four rounds of annual MDA, a reduction in S. mansoni prevalence was seen in CCA (93.9% in year 1-87.7% in year 5; P = 0.007) and KK (73.9% in year 1-59.4% in year 5; P < 0.0001). The prevalence of heavy-intensity infections roughly halved from 23.7% to 10.1% (P < 0.0001), and the mean intensity of infection fell by 55.0% (480.2-216.3 eggs per gram of feces). A malacological survey found Biomphalaria pfeifferi snail intermediate hosts in multiple water contact sites including rice paddies, streams, and Nosivolo River. Despite reductions in infection prevalence and intensity, schistosomiasis still poses a significant public health challenge in Marolambo district. Twice yearly MDA cycles and/or community-wide MDA are suggested to better reduce infections. Expanding health education, improving standards of water, sanitation and hygiene, and attention on snail-related control will also be important, especially in rice paddy irrigated areas.

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Figures

Figure 1.
Figure 1.
Map of Marolambo, Madagascar, with locations of human–water contact sites infested with Biomphalaria snails. This figure appears in color at www.ajtmh.org.
Figure 2.
Figure 2.
Bars representing total prevalence by CCA and Kato–Katz each year of the study, and line graph showing changes in mean EPG of infected individuals. The 95% CI intervals of CCA and Kato–Katz prevalence values and of the mean EPG are shown by vertical error lines.
Figure 3.
Figure 3.
Changes in proportion of individuals with each category of infection intensity, ascertained from the Kato–Katz methodology. Black = heavy, dark gray = moderate, light gray = light, and white = negative.
Figure 4.
Figure 4.
Line graphs showing the prevalence of children with S. mansoni by both CCA (dotted lines) and KK (solid lines), for each village. Vertical error lines represent the 95% CI of the prevalence values. This figure appears in color at www.ajtmh.org.
Figure 5.
Figure 5.
Scatterplots of EPG for each location and district total. Lines represent the linear regression plot of mean EPG with 95%CI (shaded).
See this image and copyright information in PMC

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