Fasciola hepatica and lymnaeid snails occurring at very high altitude in South America.

摘要: Fascioliasis due to the digenean species Fasciola hepatica has recently proved be an important public health problem, with human cases reported in countries of five continents, including severe symptoms and pathology, singular epidemiological characteristics, presenting endemic areas ranging from hypo- hyperendemic. One characteristics fascioliasis is link hyperendemic very high altitude regions, at least South America. The Northern Bolivian Altiplano, located (3800-4100 m), presents highest prevalences intensities known. Sequences internal transcribed spacers ITS-1 ITS-2 nuclear ribosomal DNA Altiplanic intermediate snail host Lymnaea truncatula suggest that both were introduced Europe. Studies undertaken understand how liver fluke its lymnaeid adapted extreme environmental conditions succeeded giving rise infection rates. In experimental infections lymnaeids carried out isolates sheep cattle, following aspects studied: miracidium development inside egg, infectivity miracidia, prepatent period, shedding chronobiology cercarial emergence, number cercariae shed by individual snails, survival molluscs beginning process, infected snails after end period longevity non-shedding snails. When comparing European F. L. truncatula, a longer higher production observed, related greater capacity Altiplano. These differences would appear favour transmission may interpreted as strategies associated adaptation conditions.