Histological assessment of tissue repair after treatment of human schistosomiasis.

Schistosomiasis is one of the main health problems hindering socio-economic development in Egypt. It affects millions at an early age, diminishing productivity and exerting a significant socio-economic impact. Schistosomiasis endemicity in Egypt varies in different areas. Schistosoma mansoni, with a prevalence generally ranging between 20 to 40%, has replaced Schistosoma haematobium in the Nile Delta, and the latter is now localized to upper Egypt with low endemicity levels (5-10%). The pathology of schistosomiasis consists essentially of a series of chronic inflammatory lesions produced in and around blood vessels by eggs or their products and sometimes by dead adult worms. If the ova continued to be deposited in sufficient numbers and over several years, they would ultimately lead to progressive fibrosis of the portal tracts and urinary bladder, or may be carried in blood and become trapped in the lungs, gastro-intestinal and genital tracts with only occasional association with other organs. The etiology of human pipe-stem fibrosis is still not understood. The host immune response and frequency of exposure and the time of re-infection interval appear to be involved in the overall process of fibrosis. Additional factors are probably involved in the human disease as genetic host susceptibility, malnutrition, repeated infections and repeated treatment, mixed infections including hepatitis, tuberculosis and typhoid. Reversibility of the fibrosis might be related to the proportion of the collagen types present. Immuno-histopathological demonstration of various types of collagen confirms the importance of time for administration of the treatment and period of follow-up. According to previous studies, the timing for treatment affects the reversibility of liver fibrosis emphasizing the importance of early treatment of schistosomiasis to prevent complications.