Lecture_2_Schistosomiasis _jan2008

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Slide 1:

LECTURE #2 Immunodominance and Severe Schistosomiasis Mansoni Collaborative Course on Infectious Diseases January 2008 Eduardo Finger [email protected] Harvard School of Public Health Faculdade de Ciências Médicas da Santa Casa de São Paulo Brazil Studies Program, DRCLAS, Harvard University

Schistosomiasis mansoni:

Schistosomiasis mansoni Eduardo Finger Santa Casa SP 2008

Objectives:

Objectives Acquaint students with a basic knowledge of schistosomiasis mansoni Illustrate the experience of a few countries in trying to deal with schistosomiasis Discuss what can be learned from these examples and how that applies to the project

Slide 4:

Schistosomiasis Second most prevalent tropical parasitic disease in the world (behind Malaria only) Etiologic agent: Schistosoma sp 600 million people at risk in 74 countries 200.000.000 people infected 150.000.000 oligosymptomatic 20.000.000 severe disease Between 200.000 and 800.000 deaths/year Disease watch n 4 (Nature reviews microbiology, January 2004)

Slide 5:

S. haematobium Group (Africa, the Mediterranean area and the Middle East) S. mansoni Group (Restricted to Africa. Only exception: S. mansoni is also prevalent in South America) S. haematobium Parasites humans S. mansoni Parasites humans. S. intercalatum Parasites humans S. rodhaini Parasites rodents and carnivores S. bovis Parasites cattle sheep and goats, rarely Man S. edwardiense Parasites ruminants S. mattheei Parasites primates and ruminants, rarely Man S. hippopotami Parasites the hippopotamus S. curassoni Parasites ruminants S. margrebowiei Parasites ruminants S. leiperi Parasites ruminants S. japonicum Group (East Asia) S. indicum Group (Asia) S. japonicum Parasites humans and other animals S. indicum Parasites ruminants S. mekongi Parasites humans and some other animals S. spindale Parasites ruminants and dogs S. malayensis Parasites humans (rarely) and other animals S. nasale Parasites ruminants S. sinensum Parasites rodents S. incognitum Parasites rodents, carnivores and ruminants D. Rollinson and A. J. G. Simpson: 'The Biology of Schistosomes From Genes to Latrines Preferred definitive host of Schistosome sp. in the wild

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Geographic distribution of schistosomiasis WHO archives (2002) WHO Technical Report Series, No.830, 1993

Spread of S. mansoni followed slave trade routes:

Spread of S. mansoni followed slave trade routes

Schistosomiasis: route of spread inside Brazil :

Memórias do Instituto Oswaldo Cruz Fundação Oswaldo Cruz, Fiocruz ISSN: 1678-8060 Vol. 99, Num. s1, 2004, pp. 13-19 Schistosomiasis: route of spread inside Brazil

S.mansoni life cycle:

S.mansoni life cycle

Infection:

Infection

Skin penetration by S. mansoni:

5min 10min 20 min Skin penetration by S. mansoni

Adult worm habitat:

Adult worm habitat

Destination of S. mansoni eggs:

Destination of S. mansoni eggs

Liver pathology associated with schistosomiasis:

Liver pathology associated with schistosomiasis Morbidity and mortality in schistosomiasis are due to granulomas formed around parasite eggs Normal liver Pipe-stem fibrosis in the liver

Polar forms of chronic schistosomiasis mansoni:

Polar forms of chronic schistosomiasis mansoni Intestinal: Well tolerated, can last years without significant harm to host Low morbidity and mortality Hepatosplenic: Important inflammation and fibrosis in portal spaces Extensive liver fibrosis produces portal hypertension, splenomegaly, ascites, portal-systemic shunting and gastrointestinal bleeding High morbidity and mortality

Clinical presentation of severe schistosomiasis:

Clinical presentation of severe schistosomiasis Portal hypertension Hepatosplenic shunt Esophageal varices Hemorrhages

Treatment and control:

Treatment and control Treatment: praziquantel and oxamniquine Reinfection rate is very high. Vaccine strategy: not expected to be available soon Control strategy: massive populational screening and treatment. Increase access to treated water.

Programs to control schistosomiasis:

Programs to control schistosomiasis Four pillars Mass chemotherapy (WHO guidelines) Molluscicides (chemical and/or biological) Sanitation (water and sewer treatment) Education Other factor: Urbanization

Control of Schistosomiasis: 4 different experiences:

Control of Schistosomiasis: 4 different experiences Program initiation Goal Mass treatment Molluscicides Sanitation Education Outcome Puerto Rico 1953 Reduce prevalence below 4% the erradicate Yes Yes Yes Yes Sustained s uccess Africa 50’s Partial local success but fail overall . Infection on the increase China 1949 Temporary . Prevalence on the increase Brazil 1976 Reduce prevalence below 4% the erradicate Yes Yes No No Partial Success . Reduced prevalence and morbidity

Prevalence of schistosomiasis following PECE:

Prevalence of schistosomiasis following PECE

Conclusions from the PECE:

Conclusions from the PECE no method is able, in an isolated way, to control schistosomiasis and every control program should consider the need of multidisciplinary application of existing methods; the main methods for long term control of infection are the implementation of basic sanitation conditions, potable water supply, as well as sanitary education and community participation; specific treatment in endemic areas associated to intermediary hosts control in "epidemiological important" foci is extremely relevant regarding short term morbidity control, though not sufficient to interrupt disease transmission; although schistosomiasis control, in a country like Brazil, with great vectors dissemination and population mobilization, is a difficult process, it is possible through intensification, adjustment, and continuity of programs in long term; it is necessary to develop a critical analysis of schistosomiasis control experience in Brazil, in order to redirect the program in an effective way, aiming to achieve only residual levels of infection for the next 20 or 30 years or, even better, its full control. Cienc. Cult. vol.55 no.1 São Paulo Jan./Mar 2003

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