Schistosomiasis
Schistosomiasis is one of the most imposing and widespread helminthic diseases. The immune system strives to be protective vis-à-vis Schistosoma infection, but the inevitable immunopathology may lead to fibrosis and organ dysfunction. Moreover, the skewin
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Schistosomiasis Ahmad Othman and Rashika El Ridi
Abstract Schistosomiasis is one of the most imposing and widespread helminthic diseases. The immune system strives to be protective vis-a`-vis Schistosoma infection, but the inevitable immunopathology may lead to fibrosis and organ dysfunction. Moreover, the skewing of immune response axis to polarized Th2 phenotype can impair resistance to other pathogens and has been associated with neoplasms, further complicating the clinical sequelae of schistosomiasis. Techniques and tools for diagnosing schistosomiasis are either cumbersome or lack sensitivity and specificity. Accordingly, many patients remain undiagnosed and receive no treatment. Currently, the only available drug is praziquantel; the use of which in mass treatment raises concerns about development of drug resistance. Indeed, Schistosoma infection is a fascinating model for gaining insight about the mutual interplay between host and parasite factors, which ultimately determines the overall morbidity. Despite decades of intensive research on schistosomiasis, unresolved issues are still intriguing scientists, one of which is the development of a vaccine. Fortunately, however, significant progress has been achieved towards the elimination of schistosomiasis. Information provided in this review should help opening venues for better diagnosis, treatment, and prevention of schistosomiasis.
A. Othman (*) Medical Parasitology Department, Faculty of Medicine, Tanta University, Tanta, Gharbiya, Egypt e-mail: [email protected] R. El Ridi Zoology Department, Faculty of Science, Cairo University, Cairo 12613, Egypt F. Bruschi (ed.), Helminth Infections and their Impact on Global Public Health, DOI 10.1007/978-3-7091-1782-8_3, © Springer-Verlag Wien 2014
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3.1
A. Othman and R. El Ridi
Introduction
Millions of children suffer anaemia, growth deficiency, abdominal pain, exercise intolerance, poor school performance, cognitive defects, and other sequelae resulting from infection with schistosomes. Millions of adult males and females endure fever, headache, lethargy, and lowered work capacity and quality of life because of severe lesions and damage in the liver, colon, rectum, and/or bladder and lower urinary tract consequent to the infection. At least 200,000 people die annually of haematemesis, liver failure, or cancer of the urinary bladder. Sound information is required for setting the platform for elimination of this serious affliction.
3.2
The Agent
Schistosomes are flatworms (kingdom Animalia, phylum Platyhelminthes, class Trematoda), which are exclusively different from other trematodes in having separate sexes; yet, they form pairs, mimicking the hermaphrodite condition. They are endoparasites (subclass Digenea) of an intermediate host snail where they reproduce asexually and a final vertebrate host where copulation of adult male and female leads to daily production of hundreds of eggs. They belong to the order Strigeidida, characterized by a forktailed cercaria, which infects final hosts using en
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