Obtaining the genome sequence of the mollusc Biomphalaria glabrata : a major intermediate host for the parasite causing human schistosomiasis

Freshwater snails of the genus Biomphalaria are important intermediate snail hosts for the widespread transmission of schistosomiasis in humans. This chronic and debilitating disease remains one of the most intractable public health concerns in 74 developing countries, infecting more than 200 million people. Prevalence of schistosomiasis is difficult to estimate, but according to the World Health Organization more than 600 million people are currently at risk for infection with either one or more of the three medically important schistosome species, Schistosoma mansoni, Schistosoma japonicum and Schistosoma haematobium (WHO Expert Committee, 1993). Although control measures involving the combined use of molluscicides and mass chemotherapy have been effective in slowing the spread of the disease, long-term prevention of schistosomiasis has been difficult to achieve because of re-infection in the human population following chemotherapy. Ideally, a protective vaccine against the parasite will be the best method to combat the spread of this disease, but efforts to develop a vaccine have proven to be challenging (Bergquist, 1998). Thus, with neither a vaccine nor a thorough understanding of the parasite/host interaction at both the human and snail stages of the parasite’s life cycle, we continue to make less than optimal progress in reducing transmission of schistosomiasis around the world. Added to this current situation is the decline in public health measures in several affected countries due to poverty, a rise in civil wars, and the construction of dams and new irrigation schemes in areas at most risk for schistosomiasis.