Schistosomiasis is an ancient neglected disease with effects worldwide, particularly in the tropics and subtropics. It ranks second to malaria, currently over 240 million people infected worldwide. Human infections are caused by the blood flukes genus Schistosoma primarily, S.mansoni, S. japonicum and S. haematobium. The vector is freshwater snails (Biomphalaria spp). Infected person excretes eggs, which hatch in water and release larvae called miracidia. Miracidia infects freshwater snails which multiply and produce thousands of infectious larval stages called cercariae. Cercariae emerge from the snail into surrounding water and contaminates. Humans become infected by skin contact with contaminated water. Man-made reservoirs and poorly designed irrigation schemes are the major grounds for schistosomiasis evolvement.
Currently, praziquantel and oxamniquine are the treatment regimens for schistosomiasis. Human vaccines are in the developmental stages. The other control measures are health education and improved sanitation. Nevertheless, control of the snail vector plays a major role in the successful control of schistosomiasis. Since, molluscicidal efforts using synthetic compounds are very expensive with various adverse effects, there is a growing interest in the biological methods as alternates. This chapter discusses in detail the various biological methods for the control of Schistosoma transmission through aquatic snails. They are application of (a) Bacterial pathogen such as Candidatus Paenibacillus glabratella, Bacillus thuringiensis (thuricide); (b) Plant derived saponin molluscicides such as Phytolacca dodecandra (Endod), Tetrapleura tetraptera, Balanites aegyptiaca, Agave sisalana, Ambrosia maritima, Swartzia madagascariensis, Sesbania sesban, Furcraea selloa marginata , Anacardium occidentale etc; (c) Predators such as Sciomyzidae (Marsh flies), Ostracoda (Crustacea) Macrobrachium vollenhovenii (prawn), Trematocranus placodon, Astatoreochromis alluaudi and Sargochromis codringtonii (fish), Procambarus clarkii (cray fish); (d) Competitor snails like Marisa cornuarietis (ampullarid), Melanoides tuberculata (thiarid), Planorbella duryi, Helisoma trivolvis (mollusck), Pomacea maculate (apple snail); and (e) Genetic manipulation of snails. A review on the above methods, their advantages and disadvantages, their field application, practical difficulties and evaluation effects will be included in this chapter.
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