| Summary: | <p>Abstract</p> <p>Background</p> <p>Human and animal fascioliasis poses serious public health problems in South America. In Venezuela, livestock infection represents an important veterinary problem whereas there appear to be few human cases reported, most of which are passively detected in health centres. However, results of recent surveys suggest that the situation may be underestimated in particular areas. To obtain a baseline for future fascioliasis assessment, studies were undertaken by means of rDNA ITS-2 and ITS-1 and mtDNA <it>cox</it>1 sequencing to clarify the specific status of Venezuelan lymnaeids, their geographical distribution and fascioliasis transmission capacity, by comparison with other American countries and other continents.</p> <p>Results</p> <p>Results obtained completely change the lymnaeid scenario known so far. The relatively rich lymnaeid fauna of Venezuela has been proven to include (i) <it>Lymnaea meridensis </it>and <it>L. neotropica </it>as the only native members, (ii) <it>L. cubensis </it>and <it>Pseudosuccinea columella </it>introduced from the Caribbean area, and (iii) <it>Galba truncatula </it>and <it>L. schirazensis </it>introduced from the Old World. The absence of representatives of the stagnicoline and <it>Radix </it>groups is remarkable. Four species are fascioliasis vectors: <it>G. truncatula</it>, <it>L. cubensis </it>and <it>L. neotropica</it>, which have the capacity to give rise to human endemic areas, and <it>P. columella</it>, which is a source of animal infection and is responsible for the spread of disease. Vector capacity in the apparently highland endemic <it>L. meridensis </it>is to be confimed, although may be expected given its phylogenetic relationships. Similarly as elsewhere, the non-transmitting <it>L. schirazensis </it>has been confused with <it>L. cubensis</it>, also with <it>G. truncatula </it>and possibly with <it>L. neotropica</it>.</p> <p>Conclusions</p> <p>The new scenario leads to the re-opening of many disease aspects. In Venezuela, altitude appears to be the main factor influencing fascioliasis distribution. Human infection shows an altitude pattern similar to other Andean countries, although a differing highland/lowland impact on animal infection does not appear evident. The overlap of <it>G. truncatula</it>, <it>L. cubensis </it>and probably also <it>L. neotropica </it>in temperate and cold zones suggests a higher risk for human infection in mid and high altitude areas. A lymnaeid species mapping by means of DNA markers becomes a priority to determine human and animal fascioliasis distribution in Venezuela, owing to the importance of lymnaeid vectors in defining transmission and epidemiological patterns.</p>
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