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LECTURE # 7 Schistosomiasis John David jdavid@hsph.harvard Mitermayer Reis

Collaborative Course on Infectious Diseases January 2009. LECTURE # 7 Schistosomiasis John David jdavid@hsph.harvard.edu Mitermayer Reis miter@cpqgm.fiocruz.br. Harvard School of Public Health Centro de Pesquisa Gonçalo Moniz, Fundação Oswaldo Cruz (Fiocruz)

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LECTURE # 7 Schistosomiasis John David jdavid@hsph.harvard Mitermayer Reis

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  1. Collaborative Course on Infectious Diseases January 2009 • LECTURE # 7 • Schistosomiasis • John David • jdavid@hsph.harvard.edu • Mitermayer Reis • miter@cpqgm.fiocruz.br Harvard School of Public Health Centro de Pesquisa Gonçalo Moniz, Fundação Oswaldo Cruz (Fiocruz) Brazil Studies Program, DRCLAS, Harvard University

  2. Objectives • To understand the Schistosomiasis lifecycle, which is essential for controlling the disease. • To consider the factors (e.g., SES, environmental) that contribute to the persistence of the diseases • To discuss different control strategies and how to prioritize them

  3. The most important first step to understand Schistosomiasis and how to control it is to know the details of the life cycle. The cycle shows how humans are infected and keep the cycle going. This is crux for control of the disease. It should becomes clear that were there proper sanitation and a supply of clean water there essentially would be no S. mansoni or S.hematobium. Control of S.japonicum is more complicated as it is a zoonosis, water buffalo and pigs and other animals being involved.

  4. DISCOVERY OF THE SCHISTOMIASIS PARASITE Bilharz in 1852 described trematode worms recovered from postmortems in Egypt, demonstrated relationship to hematuria and eggs with terminal spine in the urine. He also described terminal and lateral spine eggs in the same female worm and concluded that only one species Infected man. This was S, hematobium. Manson later described schistosomiasis in patients in the West Indies and this was called S.mansoni. Parajá da Silva in Brazil in1908 described schistosomes which produced lateral spine eggs and showed that the adults were also different from S. hematobium, and thus showed that S.mansoni was a different species.

  5. These granuloma lead to fibrosis and cause the pathology you saw in the patient, The Schistosomes induce this inflammatory reaction, not to harm their host, but so that some of the eggs that are swept through the blood to the bowel can use this inflammatory process to make their way to the lumen and out into the water. The pathology thus can be considered as “collateral damage” necessary for their survival. How can we prove this?

  6. Mice infected by S.mansoni that lack the capacity to induce a cell-mediated reaction necessary for granuloma formation do not excrete the eggs.

  7. WHY EDUCATING PEOPLE ABOUT HOW THEY GET INFECTED BY SCHISTOS0MES IS NOT ENOUGH

  8. THE PRIVATE PLACE AWAY FROM THE CROWD WERE PEOPLE DEFACATE IN THE STREAM,

  9. Methods to determine places where cercaria are present in the water

  10. Questions for Discussion • In terms of trying to control Schistosomiasis, what would be your top priorities? • In terms of trying to invest in research, what would be your top priorities?

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