New insight in lymnaeid snails (Mollusca, Gastropoda) as intermediate hosts of Fasciola hepatica (Trematoda, Digenea) in Ecuador

Fasciolosis is a widely distributed disease in livestock in South America but knowledge about the epidemiology and the intermediate hosts are scarce in Ecuador. During 3 months, lymnaeid snails were sampled (n=1482) in Pichincha province in two sites located in a highly endemic area. The snails were identified (based on morphology and ITS2 sequences) and the infection status was established through microscopic dissection and a multiplex PCR-based technique. If morphologic-based techniques were not useful to accurately named the one species collected, alignment study ascribed it to L. schirazensis. Rediae were observed in 1.75 % (26/1482) and Fasciola sp. DNA was detected in 6% (89/1482) of the collected snails. The COX1 region permitted the parasite species identification: F. hepatica. The relative sensitivity and specificity of the microscope related to the PCR results was 25.84% and 99.78% respectively. The mean size of the snails recorded positive for F. hepatica through crushing and microscopy was significantly higher than the mean size of negative snails. There was not such difference in PCR positive snails. The role of G. schirazensis as an intermediate host of F. hepatica in Ecuador is discussed and a hypothesis of an adaptation of the snail to the trematoda is formulated. For the first time, an epidemiological survey, based on molecular biology-based techniques assessed the role of lymnaeid snail in the epidemiology of fasciolosis in Ecuador.