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Population genetic studies are efficient for inferring the invasion history based on a comparison of native and invasive populations, especially when conducted at species scale. An expected outcome in invasive populations is variability loss, and this is especially true in self-fertilizing species. We here focus on the self-fertilizing Pseudosuccinea columella, an invasive hermaphroditic freshwater snail that has greatly expanded its geographic distribution and that acts as intermediate host of Fasciola hepatica, the causative agent of human and veterinary fasciolosis. We evaluated the distribution of genetic diversity at the largest geographic scale analysed to date in this species by surveying 80 populations collected during 16 years from 14 countries, using eight nuclear microsatellites and two mitochondrial genes. As expected, populations from North America, the putative origin area, were strongly structured by selfing and history and harboured much more genetic variability than invasive populations. We found high selfing rates (when it was possible to infer it), none-to-low genetic variability and strong population structure in most invasive populations. Strikingly, we found a unique genotype/haplotype in populations from eight invaded regions sampled all over the world. Moreover, snail populations resistant to infection by the parasite are genetically distinct from susceptible populations. Our results are compatible with repeated introductions in South America and flash worldwide invasion by this unique genotype/haplotype. Our study illustrates the population genetic consequences of biological invasion in a highly selfing species at very large geographic scale. We discuss how such a large-scale flash invasion may affect the spread of fasciolosis.

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We report the first evidence of natural infection of

BackgroundFreshwater lymnaeid snails can act as the intermediate hosts for trematode parasites such as the liver fluke Fasciola hepatica, that cause significant economic and biomedical burden worldwide, particularly through bovine fascioliasis. Transmission potential is tightly coupled to local compatibility with snail hosts, so accurate identification of lymnaeid species is crucial for understanding disease risk, especially when invasive species are encountered. Mendoza Province, in Argentina, is a center of livestock production and also an area of endemic fascioliasis transmission. However, the distribution of lymnaeid species in the region is not well known.MethodsThis study examined lymnaeid snails from seven localities in the Department of Malarguë, Mendoza Province, using morphological and molecular analyses and also describing ecological variables associated with snail presence.ResultsWhile morphological characters identified two species of lymnaeid, Galba truncatula and G. viatrix, molecular data revealed a third, cryptic species, G. neotropica, which was sympatric with G. viatrix. G. truncatula was exclusively found in high altitude (>1900 meters above sea level [masl]) sites, whereas mixed G. neotropica/G. viatrix localities were at middle elevations (1300–1900 masl), and G. viatrix was found alone at the lowest altitude sites (<1300 masl). Phylogenetic analysis using two mitochondrial markers revealed G. neotropica and G. viatrix to be closely related, and given their morphological similarities, their validities as separate taxonomic entities should be questioned.ConclusionsThis study highlights the need of a robust taxonomic framework for the identification of lymnaeid snails, incorporating molecular, morphological and ecological variables while avoiding nomenclature redundancy. As the three species observed here, including one alien invasive species, are considered hosts of varying susceptibility to Fasciola parasites, and given the economic importance of fascioliasis for livestock production, this research has critical importance for the ultimate aim of controlling disease transmission.

2015): New record for Galba neotropica (d'Orbigny, 1835) in Argentina, with a detailed analysis of its morphology and molecular characteristics, Molluscan Research, We report for the first time the presence of Galba neotropica in Santa Fe province, Pampean Argentina. Until the present work, the identity of the intermediate host of Fasciola hepatica in this region, the most important livestock production area of Argentina, was unknown. This report extends the geographic distribution of G. neotropica and is the first to provide molecular and morphological information on this species in Argentina. During summer 2013, snails were collected on private livestock farms with high prevalence of fasciolosis in cattle. Specimens were identified by using the nuclear sequences of the internal transcribed spacers ITS-1 and ITS-2, the shell and the shape and size of the male reproductive organs. Molecularly, ITS-1 and ITS-2 nuclear sequences exhibit 100% nucleotide identity with G. neotropica from Lima, Peru. Morphologically, G. neotropica from Santa Fe province was indistinguishable from Galba viatrix and Galba cubensis, the other two cryptic species within this South American group of lymnaeids. The combination of molecular and morphological analyses is strongly recommended to identify lymnaeids at species level. The identity of the intermediate host and the subsequent knowledge of its susceptibility, behaviour, distribution, ecology and biology are important components in developing effective measures to control fasciolosis.

<p>La fasciolosis es una enfermedad producida por Fasciola hepatica. Esta parasitosis produce grandes pérdidas económicas en el ganado bovino de la Provincia de Corrientes, Argentina, y también tiene carácter zoonótico. En el norte de la Provincia, Pseudosuccinea columella es el caracol involucrado en la transmisión de la enfermedad. El objetivo del presente trabajo fue ampliar los datos sobre la distribución de P. columella y su infestación natural por F. hepatica en la Provincia de Corrientes. Se recolectaron caracoles en un establecimiento ganadero del Departamento de Santo Tomé, al nordeste de la Provincia, que fueron identificados taxonómicamente, medidos y disecados para verificar la presencia de cercarias de F. hepatica. Los 115 caracoles recolectados fueron identificados como P. columella. La longitud de la conchilla varió entre 0,8–21,3 mm, con una media de 10,0 mm. La prevalencia de caracoles naturalmente infestados por F. hepatica fue de 8 (7,4%) sobre 108 examinados. La presencia de P. columella en distintos departamentos del norte y nordeste de la Provincia de Corrientes y las altas prevalencias de infestación natural por F. hepatica registradas, indicarían el asentamiento de un ciclo de transmisión enzoótica en esta zona.</p>

Pseudosuccinea columella (Say, 1817) is a widely distributed freshwater lymnaeid snail (Madsen and Frandsen 1989). Its role in the transmission of Fasciola hepatica (Linnaeus, 1758), the causative agent of fasciolosis, has been demonstrated in several countries of South America (