Distribution of Lymnaeidae (Mollusca: Pulmonata), intermediate snail hosts of Fasciola hepatica in Venezuela

Abstract

An extensive malacological survey was carried out between [2005][2006][2007][2008][2009] Fascioliasis is a parasitosis mainly infecting cattle, but it is now considered to be an emergent disease in humans in many countries over the world (Mas-Coma 2005). In the New World, it is considered as a serious health problem in several Andean countries. Bolivia is even described as a hyperendemic area and one of its epidemiological characteristics is its very high altitude at more than 4,000 m . The timing of the emergence of human foci in the Altiplano Region corresponds to the invasion by the European intermediate snail host Lymnaea truncatula (Jabbour-Zahab et al. 1997, Meunier et al. 2001. In Venezuela, human fascioliasis was first reported in 1910 and only eight sporadic cases were detected in the following decades (Risquez 1929, Rodríguez & González 1975, Abdul-Hadi et al. 1996, Scorza et al. 1999, Incani et al. 2002, Alarcón de Noya et al. 2006). However, in 2005 five children belonging to the same family were detected with fascioliasis in Timotes, in the Venezuelan Andes, at an altitude of 2,230 m (Alarcón de Noya et al. 2007). The same year a malacological survey carried out in the Timotes area found only a single lymnaeid species, the European L. truncatula. In this paper we present the results of an extensive malacological survey which was carried out A malacological survey was carried out between 2005-2009 across the whole country. A total of 298 sites were sampled (see the inserts in the maps showing all the sampling sites). Snails were sampled from different vegetation either by hand or sampled using a scoop mounted with a wooden handle, depending on the type of site. These sites include the following main habitat types: springs, ditches, brooks, canals, rivers, swamps, tanks, ponds and lakes. Following field collection lymnaeid snails were allowed to relax overnight using menthol. They were then immersed for 40 s in water at 70°C, from which they were transferred to water at RT. The soft parts were drawn from the shell with small forceps and fixed in slightly modified Railliet-Henry fluid (distilled water 930 mL, sodium chloride 6 g, formalin 50 mL, glacial acetic acid 20 mL). Shells were measured to the nearest 1 mm using callipers. Snails preserved in Railliet Henry's fluid were dissected under a stereoscopic microscope and drawings of the reproductive system were made using a camera lucida attachment. Snails were identified according to conchological and anatomical characteristics

New record forGalba neotropica(d'Orbigny, 1835) in Argentina, with a detailed analysis of its morphology and molecular characteristics

“…As can be seen in Table 2, this feature is characterised by high variability within populations, which makes species identification difficult and is why they are considered to be cryptic species. Although anatomical measurements of G. cubensis have never been reported, drawings of internal anatomy of that species are very similar to those of G. viatrix and G. neotropica (Pointier et al 2009). The high variability of morphological characteristics analysed in this paper (as in the most performed in this group of lymnaeids), does not allow us to know the identity of the snails because their values are overlapping (Table 2).…”

A new baseline for fascioliasis in Venezuela: lymnaeid vectors ascertained by DNA sequencing and analysis of their relationships with human and animal infection

“…Surprisingly high prevalences of 39-43% were also reported from non-classified lymnaeids in different habitats in another farm of Mérida [82]. After the addition of L. cousini [33] and inclusion of G. truncatula , the four aforementioned species were noted as the only lymnaeids found in Venezuela within the very recent country wide malacological review [34]. …”

“…Moreover, a detailed morphometric comparison allowed the differentiation of both species by many anatomical characteristics [22]. The finding of another lymnaeid population in the relatively near locality of Paso del Cóndor, at an altitude of 4040 m, recently ascribed to L. cousini [34], may most probably also concern L. meridensis . Both 18S gene sequence and the phylogenetic analysis based on ITS sequences supported a close evolutionary relationship between L. meridensis and L. cousini , suggesting an old common origin and a probable endemic divergence of L. meridensis by isolation in Venezuelan highlands [22].…”

“…However, subsequent extensive DNA marker sequencing proved that indeed not only one but several different, yet similar species had been confused under the name of L. cubensis in Venezuela. Additionally, Lymnaea cousini , hithterto only known from Ecuador and Colombia [29], has recently been described and reported in Venezuela [33,34]. …”

The first record of Galba cubensis (L. Pfeiffer, 1839) (Mollusca: Gastropoda: Lymnaeidae) from open fields of Europe

“…Probably the most important vectors are G. cubensis (L. Pfeiffer, 1839) and G. truncatula (O. F. Müller, 1774). G. cubensis is one of the most important intermediate hosts of Fasciola hepatica Linnaeus, 1758 in the Caribbean area (Pointier et al 2009, alba et al 2015, VázQuez et al 2015, the southern United States (cruz-reyeS & MaleK 1987), and a potential intermediate host of Fascioloides magna Bassi, 1875(ViGnoleS et al 2014). In the south-eastern United States G. cubensis plays an important role as an intermediate host of Heterobilharzia americana Price, 1929 which infects several mammals, including horses (coraPi et al 2015).…”