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

Abstract

BackgroundHuman 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 cox1 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.ResultsResults obtained completely change the lymnaeid scenario known so far. The relatively rich lymnaeid fauna of Venezuela has been proven to include (i) Lymnaea meridensis and L. neotropica as the only native members, (ii) L. cubensis and Pseudosuccinea columella introduced from the Caribbean area, and (iii) Galba truncatula and L. schirazensis introduced from the Old World. The absence of representatives of the stagnicoline and Radix groups is remarkable. Four species are fascioliasis vectors: G. truncatula, L. cubensis and L. neotropica, which have the capacity to give rise to human endemic areas, and P. columella, which is a source of animal infection and is responsible for the spread of disease. Vector capacity in the apparently highland endemic L. meridensis is to be confimed, although may be expected given its phylogenetic relationships. Similarly as elsewhere, the non-transmitting L. schirazensis has been confused with L. cubensis, also with G. truncatula and possibly with L. neotropica.ConclusionsThe 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 G. truncatula, L. cubensis and probably also L. neotropica 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.

DNA multigene sequencing of topotypic specimens of the fascioliasis vector Lymnaea diaphana and phylogenetic analysis of the genus Pectinidens (Gastropoda)

“…Therefore, in Lymnaeidae it has been more recently concluded that (i) rDNA markers are the appropriate targets when dealing with systematic-taxonomic and phylogenetic aspects, as well as for molecular characterization of species by haplotyping, (ii) mtDNA markers are more convenient for population and intraspecific variability studies and (iii) both rDNA and mtDNA markers may be used for the classification of specimens (Bargues et al 2011a). The 18S sequence of L. diaphana (1848 bp) is slightly longer than that of G. truncatula (1,843 bp) (Bargues et al 1997), equally long than that of L. humilis (1,848 bp) (Bargues et al 2011a), similar to that of the European stagnicolines L. stagnalis, O. glabra and L. (S.) palustris, the radicines R. auricularia and R. balthica, as well as to P. columella (ranging between 1,849-1,852 bp) (Bargues et al 1997(Bargues et al , 2011b, but pronouncedly shorter than that of L. cubensis, L. viatrix and L. neotropica (all three 1,860-bp long) (Bargues et al 2007). This suggests that L. diaphana may be considered an old species within the family Lymnaeidae, according to their phylogeny in which the oldest lymnaeid fossil known is Galba from the Jurassic (zilch 1959(zilch -1960(zilch , Inaba 1969), a shorter sequence would be the plesiomorphic condition and an increase in sequence length would have occurred during lymnaeid evolution .…”

“…Sequence comparisons -The following sequences from GenBank and European Molecular Biology Laboratory (EMBL) have been used for comparison and/or phylogenetic analyses: (i) 18S rRNA gene: complete sequences of Lymnaea (Lymnaea) stagnalis (GenBank accession z73984), Lymnaea (Stagnicola) palustris (z73983), Omphiscola glabra (z73982) and G. truncatula (z73985) (Bargues & Mas-Coma 1997), Lymnaea cubensis (z83831) (Bargues et al 1997(Bargues et al , 2007, L. viatrix and Lymnaea neotropica (both species with the same sequence AM412222) (Bargues et al 2007), Lymnaea humilis (FN182190) (Bargues et al 2011a) and Pseudosuccinea columella (FN598152) (Bargues et al 2011b), Radix auricularia (z73980) and Radix balthica (z73981) (Bargues & Mas-Coma 1997, Bargues et al 1997. Other lymnaeid incomplete sequences available in the GenBank have not been used to avoid problems in comparative sequence analyses.…”

“…Chile: A: water collection inhabited by the species in a view to the Strait (see sea on the background); B: another water collection inhabited by the species in a view to the inland; C: specimens rarely found out of water, on a floating leaf; D: stony water ground on which specimens were usually found. (Hanelt et al 1997) and Bulinus truncatus (Jorgensen et al 2011) were included for comparison purposes; (ii) rDNA ITS-2: L. (S.) palustris palustris (AJ319620), Lymnaea (Stagnicola) fuscus (AJ319621) and Catascopia occulta (AJ319642) (Bargues et al , 2003, Catascopia catascopium (AF013143), Catascopia emarginata (AF013141, AF013142), Catascopia elodes (AF013138) and Hinkleyia caperata (AF013139) (Remigio & Blair 1997b), G. truncatula H1 (AJ296271) , L. cubensis H1 (AM412223) and H2 (FN182200) (Bargues et al 2007(Bargues et al , 2011a, L. viatrix H1 (AM412224) and L. neotropica H1 (AM412225) (Bargues et al 2007), L. humilis H1 (FN182191) (Bargues et al 2011a), P. columella H1 (FN598155) (Bargues et al 2011b), R. auricularia (AJ319628) and R. balthica (AJ319633) …”

“…and C. occulta (AJ626858) (Bargues et al 2006) (Bargues et al 2011a), P. columella (PCU82073) (Remigio & Blair 1997a); (v) mtDNA cox1 gene: S. elodes (AY227368), F. bulimoides (AY227367) and Austropeplea tomentosa (AY227365) (Remigio & Hebert 2003), G. truncatula from Spain (AM494011) (Bargues et al 2007) and Germany (EU818799) (Albrecht et al 2008), L. cubensis cox1a (AM494009) and cox1b (FN182205), L. neotropica cox1a (AM494008) and cox1b (FN356741), L. humilis cox1a, cox1b and cox1c (FN182197-9) (Bargues et al 2007, 2011a, Mera y Sierra et al 2009), P. columella (FN598165) (Bargues et al 2011b) and P. columella (AY227366) (Remigio & Hebert 2003), Radix rubiginosa (GU451737) (Liu et al 2010).…”

A multiplex PCR for the detection of Fasciola hepatica in the intermediate snail host Galba cubensis

“…In the Caribbean area, the lymnaeid snail Galba cubensis (formerly known as Lymnaea (Fossaria) cubensis) is considered the main intermediate host of F. hepatica (Gutiérrez et al, 2011). However, its presence in some regions of North (Kaplan et al, 1997) and South America (Bargues et al, 2011;Medeiros et al, 2014), where it co-exist with other snail hosts complicates the epidemiological scenario of fasciolosis. Several investigations have been conducted, mainly in Cuba where fasciolosis is endemic in livestock, regarding the role of G. cubensis in F. hepatica transmission (Vázquez et al, 2014), its ecology and distribution (Cañete et al, 2004;Vázquez et al, 2009), and control strategies for its management (Perera et al, 1991).…”