India is uniquely positioned with regard to schistosomes and schistosomiasis—discovering seven new mammalian species with the existence of three more schistosome species: Orientobilharzia turkestanicum, O. harinasutai, and Schistosoma haematobium(?). An endemic focus of urinary schistosomiasis was reported from Gimvi village of Ratnagiri, Maharashtra with infrequent occurrence of schistosome eggs in human stools. Cercarial dermatitis has been reported to be more abundant in rural population using ponds, tanks, and so forth, for their domestic purposes. Few dermatitis cases were tested positive by CHR. Schistosome antigen was also detected in urine of five cases suggesting existence of active schistosomiasis in India. Nevertheless, human kind does not appear to be the usual host for Indian schistosomes in contrast to S. haematobium, S. mansoni, or S. japonicum. Various reasons for this phenomenon are discussed including evolution of Indian schistosomes, immune mechanisms, and environmental conditions. These and other aspects such as seasonal effect on the prevalence, snail infectivity, heterologous mating, existence of hybrids, and number of schistosomes in heterologous infections need further investigations with application of molecular techniques. Joint efforts by the national as well as international scientific community would be much more rewarding for better understanding of the parasite and the infection. 1. Introduction India is uniquely positioned with regard to schistosomes and schistosomiasis—discovering seven new schistosome species, namely, Schistosoma indicum, S. spindalis, S. bomfordi (Montgomery, 1906), S. incognitum (Chandler,1926), S. nasalis (Rao, 1933), S. nairi (Mudaliar and Ramanujachari, 1945), and Orientobilharzia dattai (Dutt and Srivastava, 1955). Additionally, prevalence of O. turkestanicum in Srinagar has been confirmed by Dutt and Srivastava [1], while presence of O. harinasutai in buffaloes has been suspected long back [2]. This is the country where an endemic area may harbor as many as five schistosome species [3], leading to its own complexities. In contrast to African schistosomes, the life cycle of these blood flukes involves snails inhabiting no big rivers but stagnant water bodies, that is, ponds, tanks, marshy land, agricultural fields, and so forth. Even with presence of nine schistosome species, existence of human schistosomiasis is marred with controversies despite confirming an endemic focus of urinary schistosomiasis (probably by a new schistosome species) in Gimvi village of Ratnagiri district, Maharashtra [4,
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