Rapid identification of lymnaeid snails and their infection with Fasciola gigantica in Thailand

Freshwater snails of the family Lymnaeidae are the intermediate hosts of the liver fluke Fasciola worldwide. While distinct species have been identified at the molecular level in other parts of the world such data have not been published for Thailand. In this study we collected Lymnaeidae from different localities across Thailand and analyzed their 16S rDNA sequences as a molecular signature for classification. In addition to the ubiquitous Radix rubiginosa, we have confirmed the presence of Austropeplea viridis and Radix swinhoei, for the latter of which the ribosomal rDNA sequences are reported for the first time, in North-Thailand. Based on the obtained 16S rDNA data three primer pairs were designed that allowed rapid identification of these snail species by PCR. To determine their infection status, PCR primers for F. gigantica cathepsin L were used in parallel with the snail 16S rDNA species-specific primers in multiplex PCR analyses. Western blot analysis of total snail protein with a monoclonal anti-F. gigantica cathepsin L antibody confirmed positive cathepsin L PCR results. The developed diagnostic PCR will be of use in risk assessment for transmission of fascioliasis in Thailand.