Freshwater pulmonate snails of the genus Biomphalaria are intermediate hosts of the widely distributed parasite of humans, the digenetic trematode Schistosoma mansoni. This parasite is one of the causal agents of intestinal schistosomiasis, an incapacitating disease that currently affects greater than 200 million people worldwide.This host-parasite relationship has become a model system of great interest for assessment of snail-schistosome interactions.

Expressed sequence tags (ESTs) are single-pass DNA sequence reads of short stretches of sequences obtained from cDNA libraries. The strategy has been used by many parasitology programs in a number of valuable ways: in identifying snail homologues of genes previously described in other species; for identifying transcribed regions of the genome useful for genome annotation and analysis; for the detection of splice variants and alternative polyadenylation gene isoforms; in the discovery of single nucleotide polymorphisms (SNPs) and for expression studies.

Aiming to contribute to the understanding of the complex molecular mechanisms controlling the snail-schistosome interactions, we have carried out a broad analysis of ESTs present in the public sequence database (dbEST), a division of GenBank that contains sequence data and other information on cDNA sequences, Expressed Sequence Tags, from a number of organisms.Approximately 54,000 sequences have been organized according their tissue of origin, clustered and submitted to a pipeline of tools that take these sequences and performs their functional annotation of them enabling the comparative analysis of functional terms assessed for gene ontology assignments that could be related to tissue-specific patterns.