RESUMO
The economic importance of fascioliasis in the livestock industry in the state of Rio Grande do Sul was assessed through the Federal meat inspection at major slaughter houses. Annual average rates of the livers condemned by Fasciola hepatica infection at the houses in the state have been recorded as 12-13% in cattle and 7% in sheep, respectively. Many farms in the provinces of the frontier regions of Brazil with Uruguay are contaminated with F. hepatica and acute fascioliasis with a high mortality among sheep flocks frequently occurs during the wet and cold winter season in the lowland areas of the regions. The two Lymnaeid snails, Lymnaea viatrix and L. columella are distributed in the state and act as intermediate hosts of F. hepatica. The former species, called the "mud snail", is more predominant than the latter: "pond snail".