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

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  • 1 Royal United Hospitals Bath NHS Foundation Trust, Bath, United Kingdom;
  • 2 The University of Manchester Faculty of Biology Medicine and Health, Manchester Academic Health Centre, Manchester, United Kingdom;
  • 3 Unité d’Epidémiologie et de Recherche Clinique, Institut Pasteur de Madagascar, Antananarivo, Madagascar;
  • 4 Faculté de Médecine, Université d’Antananarivo, Antananarivo, Madagascar;
  • 5 Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom;
  • 6 Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom;
  • 7 World Health Organization, Madagascar Country Office, Antananarivo, Madagascar;
  • 8 Ministère de la Santé Publique de Madagascar, Antananarivo, Madagascar

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.

Author Notes

Address correspondence to Stephen A. Spencer, Post-Graduate Medical Centre, Royal United Hospital, Combe Park, Bath BA1 3NG, United Kingdom. E-mail:

Financial support: Biotechnology and Biological Sciences Research Council (BBSRC) school regional champion funds and DTP funds awarded to S. M. C. American Association for the Advancement of Science (AAAS) Leshner fellowship funds awarded to S. M. C. British Society of Immunology Communicating Immunology Grants awarded to S. A. S., S. M. C., K. H., and J. M. St. J. P. Scientific Exploration Society Rivers Award for Health and Humanities awarded to S. A. S. Royal Geographical Society Geographical Fieldwork Grant awarded to S. A. S.

Authors’ addresses: Stephen A. Spencer, Cortland Linder, James M. St. J. Penney, Hannah J. Russell, Kate Hyde, Caitlin Sheehy, and Sheena M. Cruickshank, University of Manchester Medical School, Manchester, United Kingdom, E-mails:,,,,,, and Alice Reid, and J. Russell Stothard, Liverpool School of Tropical Medicine, Liverpool, United Kingdom, E-mails:, and Emmanuel H. Andriamasy, Gina U. Raderalazasoa, Daniel A. L. Rakotomampianina, Anjara M. Nandimbiniaina, Tahiry N. Ranaivoson, and Antsa Andrianiaina, Faculté de Médecine, Université d’Antananarivo, Antananarivo, Madagascar, E-mails:,,,,, and Amaya L. Bustinduy, London School of Hygiene and Tropical Medicine, London, United Kingdom, E-mail: Glenn T. Edosoa, and Alain M. Rahetilahy, Ministère de la Santé Publique de Madagascar, Antananarivo, Madagascar, E-mails:, and