Human and animal fascioliasis in andean regions of argentinalymnaeid vectors and livestock reservoirs

Resumen

Fascioliasis is a zoonotic parasitic disease caused in the American continent by Fasciola hepatica. It is responsible for severe economic losses to the livestock industry and is an important public health problem worldwide. Andean regions have the highest prevalences in humans ever described. The epidemiological scenario differs according to the species of lymnaeid vector involved. In Argentina, there has been great confusion referred to the species of lymnaeid vectors present. Few studies have focused on the role as reservoirs of other species beside cattle and human fascioliasis has been considered a sporadic, infrequent disease. The aim of this study is to characterise the lymnaeid species involved in the transmission of fascioliasis in Andean regions of Argentina, their relation with human and animal fascioliasis and the role as reservoirs of livestock and wild species. Lymnaeid snails were genetically and phenotypically characterised and parasitological studies were performed in livestock and wild animals. A thorough bibliographical search and analysis of human fascioliasis was done. Molecular markers used in lymnaeids were the 18S and 16S genes, the ITS-1 and the ITS-2 spacers of the nuclear ribosomal DNA and the cox1 gene of the mitochondrial DNA. The bibliographical search elevated the cases described for Argentina in previous studies from 85 to 629, the majority in mountainous regions. Results demonstrated that in Andean regions, besides Lymnaea viator, there are two other species; Galba truncatula and Lymnaea neotropica, the latter naturally infected with F. hepatica and associated with a high prevalence in domestic animals. Cattle fascioliasis showed to increase with altitude and a high prevalence was found in goats and also in autochthonous as well as introduced wild species, which adds to the epidemiological complexity. The diverse species of lymnaeids found, their extreme adaptation to different environments, the high prevalence in domestic and wild animals and the historical underestimation of human fascioliasis alert us of the real situation of fascioliasis in Andean regions of Argentina.