Assessment of the Age-Specific Disability Weight of Chronic Schistosomiasis japonica/Evaluation Du Poids Dans L'incapacite Par Age De la Schistosomiase Sino-Japonaise chronique/Evaluacion del Peso De la Discapacidad Por Edades Por Esquistosomiasis Japonica Cronica

Introduction Schistosomiasis japonica is caused by the trematode Schistosama japonicum, which is the only human blood fluke that occurs in China. Although significant progress has been made in controlling schistosomiasis in China, the disease remains of considerable public health significance, particularly in lake and marshland regions. (1-3) The other two main human schistosome species are S. haematobium and X mansoni. (4) An infection with schistosomes is often followed by acute Katayama fever or nonspecific symptoms. If left untreated, an infection develops into a chronic condition characterized by hepatosplenic disease and impaired physical and cognitive development. (1) The Global Burden of Disease study estimated the burden of schistosomiasis at 1.7 million disability-adjusted life years lost in 2002, mainly as a result ofmorbidity. (5,6) However, recent reports and a meta-analysis suggest that the global burden of schistosomiasis might be several times higher. (7-9) This discrepancy might be explained by the paucity of community-based data on the distribution and severity of nonfatal health outcomes caused by schistosomiasis and the challenges of estimating schistosome disability weights that are species-specific. The following observations prompted us to reassess the disability weight of chronic schistosomiasis japonica. First, the age-specific disability weights used in the Global Burden of Disease study were very low, namely 0.005 among those aged The consequences of chronic schistosomiasis are many and various but are mainly governed by two aspects. First, there is direct morbidity resulting from pathological changes and clinical manifestations induced by the deposition of schistosome eggs in tissues and the subsequent inflammatory immune reactions and calcification of dead eggs. This may cause hepatomegaly, splenomegaly, hepatic fibrosis and various other symptoms, including abdominal pain, diarrhoea and blood in the stool. Second, additional morbidity also associated with schistosomiasis (for example, anaemia, growth retardation and cognitive impairment) is nonspecific and thus it may be difficult to tease apart from morbid sequelae caused by other diseases. (9,11) Moreover, it may be difficult to identify chronic cases and to assess people's health status in endemic settings where multiparasitism is the norm rather than the exception. (1,12) The advent of portable ultrasound devices (13) and progress made with questionnaires for self-reported health (for example, the EuroQol Group's quality of life questionnaire known as EQ-5D) (14,15) offer new avenues for obtaining community-based estimates of the disability weight caused by chronic schistosomiasis. Abdominal ultrasonography allows the direct visualization of pathology in the liver and spleen and facilitates the quantification of disease progression and resolution following treatment. (13,16-18) The EQ-5D questionnaire is a standardized instrument that measures people's health status and their quality of life. In March 2000, a version of the EQ-5D questionnaire authorized by the EuroQol Group was validated in health-related quality of lire studies in Beijing. …