Search

We present a geographical distribution map of Bulinus truncatus based on historical and current localities in Spain and Portugal, that corresponds to the risk map of urogenital schistosomiasis for this freshwater snail. We reviewed samples of the species deposited at the Museu de Ciències Naturals of Barcelona and the Museo Nacional de Ciencias Naturales of Madrid, together with our own data, including some unpublished contributions. This map will help determine the optimal area for this species and identify areas of greatest risk for urogenital schistosomiasis in the two countries. We emphasize that global change and climate change may favour the presence of both the vector (B. truncatus) and the parasite (Schistosoma haematobium) in Spain and Portugal.

Two new locations in Spain of Bulinus truncatus (Audouin, 1827) (Gastropoda, Planorbidae), intermediate host of urinary Schistosomiasis Two new populations of the planorbid snail species Bulinus truncatus were found in Spain in 2014. The first consisted of shells only, found in the lagoon of Villena (province of Alicante), which had dried up at the beginning of the 19th century. This finding is of important biogeographic interest because it links the presence of this species in northern Catalonia with its detection in southern Andalucia as this species had not been found previously in the regions of Murcia or Valencia. The second population was found in El Ejido (province of Almeria), and thousands of living specimens were found here. This allowed a complete shell characterisation and molecular assessment by means of sequencing the cox1 gene of the mitochondrial DNA genome, which showed 100% homology with sequences of other populations of the same snail species available in the GenBank. The finding of B. truncatus in Almeria is of additional value given the applied importance of this planorbid species as a vector of urinary Schistosomiasis, thus representing a risk of introduction and autochthonous transmission of the disease in Spain, as has occurred in other southern European countries in the past and recently.

Sequencing of the rDNA ITS–1 proved that the lymnaeid snail species Galba truncatula is present in Argentina and that it belongs to the haplotype HC, the same as that responsible for the fascioliasis transmission in the human hyperendemic area with the highest human prevalences and intensities known, the Northern Bolivian Altiplano.

Although, in the endemic areas throughout the world, human fascioliasis presents varying patterns in its epidemiology, the species of lymnaeid snail that act as intermediate hosts and vectors are always crucial in the transmission of the causative parasites. Species in the Galba/Fossaria group of snails, such as Lymnaea cubensis, L. viatrix var. A ventricosa, L. viatrix var. B elongata and Galba truncatula, appear to be frequently involved in the transmission of Fasciola hepatica in Central and South America, although specific classification within this morphologically and anatomically confusing group is often very difficult. To explore the potential use of molecular analyses in the identification of vector snails, regions of the ribosomal DNA — the small subunit (18S) gene and internal transcribed spacers (ITS-2 and ITS-1) — and of the mitochondrial DNA — the cytochrome c oxidase subunit I (COI) — of wild-caught lymnaeid snails of L. cubensis, L. viatrix var. A ventricosa, L. viatrix var. B elongata and G. truncatula have been sequenced. The samples of the Latin American species included specimens from the respective type localities. The genetic distances observed and the results of phylogenetic analyses demonstrate that two different species exist within L. viatrix. Lymnaea neotropica n. sp. (=L. viatrix var. B elongata) is here proposed for specimens from Lima, Peru, and is differentiated from L. viatrix (=L. viatrix var. A ventricosa), L. cubensis and G. truncatula. The data collected on the 18S ribosomal-RNA gene indicate that the snails investigated may cover more than one supraspecific taxon. The ITS-2, ITS-1 and COI nucleotide sequences are clearly useful markers for the differentiation of these morpho–anatomically similar lymnaeid species. The numerous microsatellite repeats found within ITS-2 are potential tools for differentiation at population level. [ABSTRACT FROM AUTHOR]

Fascioliasis is of well-known veterinary importance and an increasing human health problem, with reported cases in the five continents. The causative agents, Fasciola hepatica and Fasciola gigantica, present geographical distributions, which overlap in many regions of Africa and Asia, and in which the differentiation of both species is usually difficult because of the many variations in their morphological characteristics. Moreover, in humans, liver fluke classification cannot be achieved by clinical, pathological, coprological or immunological methods. The differential diagnosis between F. hepatica and F. gigantica infection is very important because of their different transmission and epidemiological characteristics. A simple and rapid PCR-restriction fragment length polymorphism (RFLP) assay, using the common restriction enzymes Ava II and Dra II, is described to distinguish between both fasciolid species. It is based on a 618-bp-long sequence of the 28S rRNA gene recently obtained from liver fluke populations of South America, Europe and Africa. This sequence showed a few nucleotide differences between both fasciolids and no intraspecific variations within each species. This assay provides unambigous results and may be useful for both individual subject diagnosis and epidemiological surveys of humans and animals in endemic regions of sympatry. [Copyright &y& Elsevier]

The taxonomic position of the Lymnaeidae from the Bolivian Altiplano has been unclear. On the basis of conchological characters, some authors reported two species from this area, Lymnaea viatrix and L. cubensis while others, considering also anatomical characters, considered L. viatrix as a synonym of L. cubensis. More recent studies demonstrated genetic identity between the Bolivian lymnaeids and L. truncatula from the Iberian Peninsula. Populations recognized as L. cubensis correspond to a distinct genetic group, but genetic information was not available for L. viatrix. In the light of these genetic results, a morphometric study of both the shell (using Raupian parameters) and male reproductive system was carried out of L. cubensis from Cuba (type locality), Dominican Republic, Guadeloupe and Venezuela, and of L. truncatula from Bolivia, France, Portugal, Spain and Morocco. Syntypes of L. viatrix from Argentina (var. A. ventricosa) and specimens of L. viatrix (var. B. elongata) from the type locality, Peru, were also studied (conchological characters only). The conchological study showed the presence of a large amount of variability between populations. This variability was not congruent with genetic results. A large amount of variability was also found using anatomical characters of the male reproductive system and all of them clearly separate L. cubensis from L. truncatula independently from geographical origin. Thus anatomical characters, unlike conchological parameters, do differentiate taxonomic species inferred from genetic studies. [ABSTRACT FROM PUBLISHER]

Calodium hepaticum is a zoonotic nematode with a worldwide distribution. Although the host range of C. hepaticum includes a wide spectrum of mammals (including humans), this parasite is predominantly associated with the families Muridae and Cricetidae. Several Sigmodontinae species from Argentina were found to be infected by C. hepaticum , with a high prevalence in Akodon azarae . The present study focuses on C. hepaticum eggs from natural infection of three species of sigmodontine rodents from Argentina. Eggs were genetically characterized (intergenic 18S rRNA region). The objectives of this work are: (i) to propose a new analytical methodology; and (ii) to morphologically characterize C. hepaticum eggs, from three Sigmodontinae species ( A. azarae , Calomys callidus and Oligoryzomys flavescens ). Analyses were made by the Computer Image Analysis System based on the new standardized measurements and geometric morphometric tools. The resulting factor maps clearly illustrate global size differences in the parasite eggs from the three Sigmodontinae species analysed. The degree of similarity between egg populations was assessed through pairwise Mahalanobis distances, showing that the largest distances were detected between parasite eggs from C. callidus and O. flavescens . Herein, the phenotypical plasticity of C. hepaticum eggs is shown. Significant positive correlations were obtained between each egg parasite principal component 1 and rodent corporal characteristics: weight; liver weight; rodent length; and rodent body condition. The usefulness of the geometric morphometric analysis in studies of the relationship between C. hepaticum and its host must be highlighted. The high prevalence observed in A. azarae , associated with the wide size range of the parasite eggs evidenced by principal component analysis, suggests A. azarae to be the Sigmodontinae host species that plays the most important role as reservoir host for C. hepaticum in the New World.

Fascioliasis is a worldwide emerging snail-borne zoonotic trematodiasis with a great spreading capacity linked to animal and human movements, climate change, and anthropogenic modifications of freshwater environments. South America is the continent with more human endemic areas caused by Fasciola hepatica , mainly in high altitude areas of Andean regions. The Peruvian Cajamarca area presents the highest human prevalences reported, only lower than those in the Bolivian Altiplano. Sequencing of the complete rDNA ITS-2 allowed for the specific and haplotype classification of lymnaeid snails collected in seasonal field surveys along a transect including 2007-3473 m altitudes. The species Galba truncatula (one haplotype preferentially in higher altitudes) and Pseudosuccinea columella (one haplotype in an isolated population), and the non-transmitting species Lymnaea schirazensis (two haplotypes mainly in lower altitudes) were found. Climatic seasonality proved to influence G. truncatula populations in temporarily dried habitats, whereas L. schirazensis appeared to be more climatologically independent due to its extreme amphibious ecology. Along the southeastern transect from Cajamarca city, G. truncatula and L. schirazensis shared the same site in 7 localities (46.7% of the water collections studied). The detection of G. truncatula in 11 new foci (73.3%), predominantly in northern localities closer to the city, demonstrate that the Cajamarca transmission risk area is markedly wider than previously considered. Lymnaea schirazensis progressively increases its presence when moving away from the city. Results highlight the usefulness of lymnaeid surveys to assess borders of the endemic area and inner distribution of transmission foci. Similar lymnaeid surveys are still in need to be performed in the wide northern and western zones of the Cajamarca city. The coexistence of more than one lymnaeid transmitting species, together with a morphologically indistinguishable non-transmitting species and livestock movements inside the area, conform a complex scenario which poses difficulties for the needed One Health control intervention., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2021 The Author(s).)

Fascioliasis is a zoonotic disease caused by liver flukes transmitted by freshwater lymnaeid snails. Donkey and horse reservoir roles have been highlighted in human endemic areas. Liver fluke infection in mules has received very limited research. Their role in disease transmission, epidemiological importance and Fasciola hepatica pathogenicity are studied for the first time. Prevalence was 39.5% in 81 mules from Aconcagua, and 24.4% in 127 from Uspallata, in high-altitude areas of Mendoza province, Argentina. A mean amount of 101,242 eggs/mule/day is estimated. Lymnaeids from Uspallata proved to belong to ribosomal DNA internal transcribed spacer (ITS) markers ITS-1 and ITS-2 combined haplotype 3C of Galba truncatula. These lymnaeids were experimentally susceptible to infection by egg miracidia from mules. Infectivity, number of cercariae/snail and shedding period fit the enhanced F. hepatica/G. truncatula transmission pattern at very high altitude. This indicates that the mule is able to maintain the F. hepatica cycle independently. Individual burdens of 20 and 97 flukes were found. Mule infection susceptibility is intermediate between donkey and horse, although closer to the latter. Anatomo-pathology and histopathology indicate that massive infection may cause mule death. Haematological value decreases of red blood cells, haemoglobin, leucocytes and lymphocytes indicate anaemia and strong immunosuppression. Strongly increased biochemical marker values indicate liver function alterations. The mule probably played a role in the past exchanges with Chile and Bolivia through Mendoza province. Evidence suggests that mules could contribute to the spread of both F. hepatica and G. truncatula to human fascioliasis-endemic areas in these countries.

The haematophagous insects of the subfamily Triatominae (Hemiptera-Reduviidae) have great epidemiological importance as vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Mepraia was originally described as a monotypic genus comprised of Mepraia spinolai, distributed along coastal areas of northern Chile (from Region I to the Metropolitan Region). Recently, some M. spinolai populations have been ranked as a new species named Mepraia gajardoi. Several populations along the distribution range of the genus were sampled, and genetic differentiation was studied based upon the analysis of three molecular markers: cytogenetics (karyotype and chromosome behaviour during meiosis using the C-banding technique), mitochondrial DNA (a cytochrome oxidase I gene fragment), and nuclear ribosomal DNA (intergenic region including the two internal transcribed spacers ITS-1 and ITS-2 and the 5.8S rRNA gene). The data here presented indicate that populations within the Mepraia genus (excluding Region II specimens) can be divided into two separate lineages. One lineage is comprised of specimens from the northernmost Region I and represents M. gajardoi. The other includes samples from the southern III, IV and the Metropolitan Regions, and represents M. spinolai. Region II individuals deserve particular attention as their relationship to the two identified lineages is not clear-cut. While they appear to belong to M. spinolai based on cytogenetics and rDNA markers, COI results indicate a closer relationship to M. gajardoi. This disagreement can be due to mitochondrial DNA introgression or the retention of ancestral polymorphisms.

In Chagas disease, triatomine vectors are the main target for control measures because of the absence of effective drugs. The broad usefulness of nuclear rDNA and mtDNA sequences explains why triatomine studies using these markers have increased so pronouncedly in recent years. This indicates the appropriateness of an updated review about these molecular markers, concentrating on aspects useful for research on Chagas disease vectors. A comparative analysis is presented on the efficiency, weight of their different characteristics, limitations and problems of each of the different DNA markers in the light of the results obtained in studies on populations, hybrids, subspecies and species of the subfamily Triatominae. The use of a standardized composite haplotype code nomenclature for both nuclear rDNA and mtDNA markers is strongly encouraged to avoid difficulties in comparative studies. Triatomine aspects related to concerted evolution, microsatellites, minisatellites and insertions/deletions in nuclear rDNA and silent/non-silent mutations, pseudogenes and weaknesses of partial sequences in mtDNA are analysed. Introgression and hybrids, nuclear and mitochondrial DNA strengths, and compared evolutionary rates of nuclear rDNA and mtDNA in triatomines are discussed. Many conclusions are obtained thanks to the availability, for the first time in triatomines, of a complete sequence of a protein-coding mtDNA gene as ND1 from very numerous triatomine species covering from different populations of a species up to members belonging to different tribes. The evolutionary rates of each nuclear rDNA marker and mtDNA marker are analysed by comparison at subspecies level (intrapopulational, interpopulational, between morphs, and between subspecies) and species level (close and distant species of the same genus, species of different genera, and species of different tribes). Weaknesses of mtDNA for systematic-taxonomic purposes detected recently and newly in insects and triatomines, respectively, are discussed in detail. Emphasis is given to taxonomic units and biological entities presenting well-known problematics, both from the systematic-taxonomic and/or epidemiological-control points of view, as well as to molecular situations which can give rise to erroneous conclusions. All these aspects constitute the background on which the key question about the systematic concepts of species and subspecies in triatomines is focused. The global purpose is to facilitate future work on triatomines by highlighting present gaps, how better choice the appropriate markers, and marker aspects which should be taken into account. Key characteristics as alpha, CI and transformation rate matrices ought to be obtained and noted to get appropriate results and allow correct interpretations. The main aim is to offer a baseline for future fundamental research on triatomines and applied research on transmission, epidemiology and control measures related to Chagas disease vectors.