Diagnosis of Schistosomiasis in Low Endemic Areas

Schistosomiasis, also known as bilharziasis is caused by snail transmitted parasites of the genus schistosoma that inhabit the human vasculature.(1,2) It is among the most important parasitic diseases worldwide, with a significant socio economic impact(3). More than 200 million people are infected, and about 200,000 may die from the disease each year. On a global scale, one of thirty individuals has schistosomiasis(4). About 779 million people live in endemic areas in the Middle East, South America, Caribbean, Southeast Asia and particularly sub-Saharan Africa(4). Extreme poverty, the unawareness of the risks, the inadequacy or total lack of public health facilities plus the unsanitary conditions in which millions of people lead their daily lives are all factors contributing to the risk of infection(5). During the past 20 years, much progress in combating the disease has been achieved based on World Health Organization recommendation strategies. Recent years have seen a notable decrease in the prevalence and morbidity of the disease in many endemic countries(6,7). Many countries of the EMR ( Eastern Mediterranean Region) namely Egypt, Iraq, Syria, Libya, Oman and Saudi Arabia have now reached low schistosomiasis endemicity. For instance, the overall prevalence of schistosomiasis in Egypt, was about 40% in (1967) before the national control program started by WHO (EMRO). In 2006, due to different control measures, the overall prevalence fell down to <3%. However there are still hot spot transmission foci with prevalence rate about 10%. Therefore lack of well structured prevention, control and elimination programs could lead to emergence or resurgence of the controlled disease. Schistosomiasis has been eliminated in Iran, Lebanon, Morocco and Tunisia, no new cases were detected over the past few years. Furthermore, WHO adopted a resolution calling on countries in low transmission areas, to sustain successful control activities in order to eliminate schistosomiasis(8) . In these conditions, where elimination of schistosomiasis is aimed for, case detection may pose a problem because the commonly used methods for the assessment of infection may lack necessary sensitivity to accurately determine the prevalence of schistosomiasis or of parasite burden(9,10). WHO(2001,2006)(11,12) asked for sensitive assays for active surveillance, specially in situations with no or very low transmission. Notwithstanding the large number of tests for diagnosing schistosomiasis, few have withstood tests of effectiveness, reproducibility, cross reactivity and predictive values (Rabello et al. 2002)(13). The diagnostic strategies traditionally rely on the detection of parasite eggs in stool (S. mansoni, S.japonicum) or urine (S. haematobium) , antibody and