Circulating Small RNA Profiling of Patients with Alveolar and Cystic Echinococcosis.

Alveolar (AE) and cystic (CE) echinococcosis are two parasitic diseases caused by the tapeworms Echinococcus multilocularis and E. granulosus sensu lato (s. l.), respectively. Currently, AE and CE are mainly diagnosed by means of imaging techniques, serology, and clinical and epidemiological data. However, no viability markers that indicate parasite state during infection are available. Extracellular small RNAs (sRNAs) are short non-coding RNAs that can be secreted by cells through association with extracellular vesicles, proteins, or lipoproteins. Circulating sRNAs can show altered expression in pathological states; hence, they are intensively studied as biomarkers for several diseases. Here, we profiled the sRNA transcriptomes of AE and CE patients to identify novel biomarkers to aid in medical decisions when current diagnostic procedures are inconclusive. For this, endogenous and parasitic sRNAs were analyzed by sRNA sequencing in serum from disease negative, positive, and treated patients and patients harboring a non-parasitic lesion. Consequently, 20 differentially expressed sRNAs associated with AE, CE, and/or non-parasitic lesion were identified. Our results represent an in-depth characterization of the effect E. multilocularis and E. granulosus s. l. exert on the extracellular sRNA landscape in human infections and provide a set of novel candidate biomarkers for both AE and CE detection.

Expression profiling of Echinococcus multilocularis miRNAs throughout metacestode development in vitro.

The neglected zoonotic disease alveolar echinococcosis (AE) is caused by the metacestode stage of the tapeworm parasite Echinococcus multilocularis. MicroRNAs (miRNAs) are small non-coding RNAs with a major role in regulating gene expression in key biological processes. We analyzed the expression profile of E. multilocularis miRNAs throughout metacestode development in vitro, determined the spatial expression of miR-71 in metacestodes cultured in vitro and predicted miRNA targets. Small cDNA libraries from different samples of E. multilocularis were sequenced. We confirmed the expression of 37 miRNAs in E. multilocularis being some of them absent in the host, such as miR-71. We found a few miRNAs highly expressed in all life cycle stages and conditions analyzed, whereas most miRNAs showed very low expression. The most expressed miRNAs were miR-71, miR-9, let-7, miR-10, miR-4989 and miR-1. The high expression of these miRNAs was conserved in other tapeworms, suggesting essential roles in development, survival, or host-parasite interaction. We found highly regulated miRNAs during the different transitions or cultured conditions analyzed, which might suggest a role in the regulation of developmental timing, host-parasite interaction, and/or in maintaining the unique developmental features of each developmental stage or condition. We determined that miR-71 is expressed in germinative cells and in other cell types of the germinal layer in E. multilocularis metacestodes cultured in vitro. MiRNA target prediction of the most highly expressed miRNAs and in silico functional analysis suggested conserved and essential roles for these miRNAs in parasite biology. We found relevant targets potentially involved in development, cell growth and death, lifespan regulation, transcription, signal transduction and cell motility. The evolutionary conservation and expression analyses of E. multilocularis miRNAs throughout metacestode development along with the in silico functional analyses of their predicted targets might help to identify selective therapeutic targets for treatment and control of AE.

A Highly Conserved Iron-Sulfur Cluster Assembly Machinery between Humans and Amoeba Dictyostelium discoideum: The Characterization of Frataxin.

Several biological activities depend on iron-sulfur clusters ([Fe-S]). Even though they are well-known in several organisms their function and metabolic pathway were poorly understood in the majority of the organisms. We propose to use the amoeba Dictyostelium discoideum, as a biological model to study the biosynthesis of [Fe-S] at the molecular, cellular and organism levels. First, we have explored the D. discoideum genome looking for genes corresponding to the subunits that constitute the molecular machinery for Fe-S cluster assembly and, based on the structure of the mammalian supercomplex and amino acid conservation profiles, we inferred the full functionality of the amoeba machinery. After that, we expressed the recombinant mature form of D. discoideum frataxin protein (DdFXN), the kinetic activator of this pathway. We characterized the protein and its conformational stability. DdFXN is monomeric and compact. The analysis of the secondary structure content, calculated using the far-UV CD spectra, was compatible with the data expected for the FXN fold, and near-UV CD spectra were compatible with the data corresponding to a folded protein. In addition, Tryptophan fluorescence indicated that the emission occurs from an apolar environment. However, the conformation of DdFXN is significantly less stable than that of the human FXN, (4.0 vs. 9.0 kcal mol-1, respectively). Based on a sequence analysis and structural models of DdFXN, we investigated key residues involved in the interaction of DdFXN with the supercomplex and the effect of point mutations on the energetics of the DdFXN tertiary structure. More than 10 residues involved in Friedreich's Ataxia are conserved between the human and DdFXN forms, and a good correlation between mutational effect on the energetics of both proteins were found, suggesting the existence of similar sequence/function/stability relationships. Finally, we integrated this information in an evolutionary context which highlights particular variation patterns between amoeba and humans that may reflect a functional importance of specific protein positions. Moreover, the complete pathway obtained forms a piece of evidence in favor of the hypothesis of a shared and highly conserved [Fe-S] assembly machinery between Human and D. discoideum.

Development of a copro-LAMP assay for detection of several species of Echinococcus granulosus sensu lato complex.

Cystic echinococcosis represents a significant problem in human and animal health and constitutes one of the most severe Neglected Tropical Diseases prioritized by the World Health Organization. The etiological agent is the complex Echinococcus granulosus sensu lato (s. l.), composed of several species/genotypes. Diagnosis in the definitive host and molecular epidemiology studies are important points for cystic echinococcosis control. Here we developed a new copro-LAMP assay, LAMP EGSL, for diagnosis in the definitive host for simultaneous detection of Echinococcus granulosus sensu stricto (s. s.), Echinococcus ortleppi, and Echinococcus canadensis species. Also, the analytical sensitivity, specificity and plausibility of performance in a rural context of a previously reported species-specific LAMP reaction, was evaluated. Both reactions showed high analytical sensitivity values (10 fg-100 fg DNA) and did not show cross reaction with DNA from host or other helminthic parasites. LAMP EGSL was performed with samples from an endemic area. In addition, the alkaline hydrolysis of one E. granulosus s. s. adult parasite followed by specific LAMP to E. granulosus s. s. was performed in a laboratory with low resources from another cystic echinococcosis endemic area. The results obtained suggest that LAMP EGSL represents a potential tool for canine diagnosis that could be useful for cystic echinococcosis control programs. In addition, we showed that LAMP reaction for E. granulous s. s., E. ortleppi and E. canadensis specific detection, could be useful for molecular epidemiology studies applicable to the definitive host. Both reactions were performed in endemic, rural areas without sophisticated equipment.

Histone deacetylase enzymes as potential drug targets of Neglected Tropical Diseases caused by cestodes.

Cestode parasites cause neglected diseases, such as echinococcosis and cysticercosis, which represent a significant problem in human and animal health. Benzimidazoles and praziquantel are the only available drugs for chemotherapy and it is therefore important to identify new alternative drugs against cestode parasites. Histone deacetylases (HDACs) are validated drug targets for the treatment of cancer and other diseases, including neglected diseases. However, knowledge of HDACs in cestodes is very scarce. In this work, we investigated cestode HDACs as potential drug targets to develop new therapies against neglected diseases caused by cestodes. Here we showed the full repertoire of HDAC coding genes in several members of the class Cestoda. Between 6 and 7 zinc-dependent HDAC coding genes were identified in the genomes of species from Echinococcus, Taenia, Mesocestoides and Hymenolepis genera. We classified them as Class I and II HDACs and analyzed their transcriptional expression levels throughout developmental stages of Echinococcus spp. We confirmed for the first time the complete HDAC8 nucleotide sequences from Echinococcus canadensis G7 and Mesocestoides corti. Homology models for these proteins showed particular structural features which differentiate them from HDAC8 from Homo sapiens. Furthermore, we showed that Trichostatin A (TSA), a pan-HDAC inhibitor, decreases the viability of M. corti, alters its tegument and morphology and produces an increment of the total amount of acetylated proteins, including acetylated histone H4. These results suggest that HDAC from cestodes are functional and might play important roles on survival and development. The particular structural features observed in cestode HDAC8 proteins suggest that these enzymes could be selectively targeted. This report provides the basis for further studies on cestode HDAC enzymes and for discovery of new HDAC inhibitors for the treatment of neglected diseases caused by cestode parasites.

microRNA analysis of Taenia crassiceps cysticerci under praziquantel treatment and genome-wide identification of Taenia solium miRNAs.

MicroRNAs (miRNAs) are small non-coding RNAs that have emerged as important regulators of gene expression and perform critical functions in development and disease. In spite of the increased interest in miRNAs from helminth parasites, no information is available on miRNAs from Taenia solium, the causative agent of cysticercosis, a neglected disease affecting millions of people worldwide. Here we performed a comprehensive analysis of miRNAs from Taenia crassiceps, a laboratory model for T. solium studies, and identified miRNAs in the T. solium genome. Moreover, we analysed the effect of praziquantel, one of the two main drugs used for cysticercosis treatment, on the miRNA expression profile of T. crassiceps cysticerci. Using small RNA-seq and two independent algorithms for miRNA prediction, as well as northern blot validation, we found transcriptional evidence of 39 miRNA loci in T. crassiceps. Since miRNAs were mapped to the T. solium genome, these miRNAs are considered common to both parasites. The miRNA expression profile of T. crassiceps was biased to the same set of highly expressed miRNAs reported in other cestodes. We found a significant altered expression of miR-7b under praziquantel treatment. In addition, we searched for miRNAs predicted to target genes related to drug response. We performed a detailed target prediction for miR-7b and found genes related to drug action. We report an initial approach to study the effect of sub-lethal drug treatment on miRNA expression in a cestode parasite, which provides a platform for further studies of miRNA involvement in drug effects. The results of our work could be applied to drug development and provide basic knowledge of cysticercosis and other neglected helminth infections.

Echinococcus oligarthrus in the subtropical region of Argentina: First integration of morphological and molecular analyses determines two distinct populations.

Echinococcosis is a parasitic zoonosis that is considered as a neglected disease by the World Health Organization. The species Echinococcus oligarthrus is one of the causative agents of Neotropical echinococcosis, which is a poorly understood disease that requires a complex medical examination, may threaten human life, and is frequently associated with a low socioeconomic status. Morphological and genetic diversity in E. oligarthrus remains unknown. The aim of this work is to identify and characterize E. oligarthrus infections in sylvatic animals from the Upper Paraná Atlantic Forest in the province of Misiones, Argentina, by following an integrative approach that links morphological, genetic and ecological aspects. This study demonstrates, for the first time, one of the complete life cycles of E. oligarthrus in an important ecoregion. The Upper Paraná Atlantic Forest constitutes the largest remnant continuous forest of the Atlantic Forest, representing 7% of the world's biodiversity. This is the first molecular determination of E. oligarthrus in Argentina. In addition, the agouti (Dasyprocta azarae), the ocelot (Leopardus pardalis) and the puma (Puma concolor) were identified as sylvatic hosts of Neotropical echinococcosis caused by E. oligarthrus. Mitochondrial and nuclear molecular marker analyses showed a high genetic diversity in E. oligarthrus. Moreover, the genetic distance found among E. oligarthrus isolates is higher than the one observed among Echinococcus granulosus genotypes, which clearly indicates that there are at least two different E. oligarthrus populations in Argentina. This study provides valuable information to understand the underlying conditions that favour the maintenance of E. oligarthrus in sylvatic cycles and to evaluate its zoonotic significance for devising preventive measures for human and animal wellbeing.

The Echinococcus canadensis (G7) genome: a key knowledge of parasitic platyhelminth human diseases.

BACKGROUND: The parasite Echinococcus canadensis (G7) (phylum Platyhelminthes, class Cestoda) is one of the causative agents of echinococcosis. Echinococcosis is a worldwide chronic zoonosis affecting humans as well as domestic and wild mammals, which has been reported as a prioritized neglected disease by the World Health Organisation. No genomic data, comparative genomic analyses or efficient therapeutic and diagnostic tools are available for this severe disease. The information presented in this study will help to understand the peculiar biological characters and to design species-specific control tools. RESULTS: We sequenced, assembled and annotated the 115-Mb genome of E. canadensis (G7). Comparative genomic analyses using whole genome data of three Echinococcus species not only confirmed the status of E. canadensis (G7) as a separate species but also demonstrated a high nucleotide sequences divergence in relation to E. granulosus (G1). The E. canadensis (G7) genome contains 11,449 genes with a core set of 881 orthologs shared among five cestode species. Comparative genomics revealed that there are more single nucleotide polymorphisms (SNPs) between E. canadensis (G7) and E. granulosus (G1) than between E. canadensis (G7) and E. multilocularis. This result was unexpected since E. canadensis (G7) and E. granulosus (G1) were considered to belong to the species complex E. granulosus sensu lato. We described SNPs in known drug targets and metabolism genes in the E. canadensis (G7) genome. Regarding gene regulation, we analysed three particular features: CpG island distribution along the three Echinococcus genomes, DNA methylation system and small RNA pathway. The results suggest the occurrence of yet unknown gene regulation mechanisms in Echinococcus. CONCLUSIONS: This is the first work that addresses Echinococcus comparative genomics. The resources presented here will promote the study of mechanisms of parasite development as well as new tools for drug discovery. The availability of a high-quality genome assembly is critical for fully exploring the biology of a pathogenic organism. The E. canadensis (G7) genome presented in this study provides a unique opportunity to address the genetic diversity among the genus Echinococcus and its particular developmental features. At present, there is no unequivocal taxonomic classification of Echinococcus species; however, the genome-wide SNPs analysis performed here revealed the phylogenetic distance among these three Echinococcus species. Additional cestode genomes need to be sequenced to be able to resolve their phylogeny.

Implementation of new tools in molecular epidemiology studies of Echinococcus granulosus sensu lato in South America.

The aim of this work was to determine Echinococcus granulosus sensu lato species and genotypes in intermediate and definitive hosts and in human isolates from endemic regions of Argentina and Brazil including those where no molecular data is available by a combination of classical and alternative molecular tools. A total of 227 samples were isolated from humans, natural intermediate and definitive hosts. Amplification of cytochrome c oxidase subunit I gene fragment was performed and a combination of AluI digestion assay, High Resolution Melting analysis (HRM) assay and DNA sequencing was implemented for Echinococcus species/genotype determination. E. granulosus sensu stricto (G1) was found in sheep (n=35), cattle (n=67) and dogs (n=5); E. ortleppi (G5) in humans (n=3) and cattle (n=108); E. canadensis (G6) in humans (n=2) and E. canadensis (G7) in pigs (n=7). We reported for the first time the presence of E. ortleppi (G5) and E. canadensis (G6) in humans from San Juan and Catamarca Argentinean provinces and E. canadensis (G7) in pigs from Cordoba Argentinean province. In this work, we widened molecular epidemiology studies of E. granulosus s. l. in South America by analyzing several isolates from definitive and intermediate hosts, including humans from endemic regions were such information was scarce or unavailable. The presence of different species/genotypes in the same region and host species reinforce the need of rapid and specific techniques for accurate determination of Echinococcus species such as the ones proposed in this work.

Cystic echinococcosis in South America: systematic review of species and genotypes of Echinococcus granulosus sensu lato in humans and natural domestic hosts.

OBJECTIVE: To systematically review publications on Echinococcus granulosus sensu lato species/genotypes reported in domestic intermediate and definitive hosts in South America and in human cases worldwide, taking into account those articles where DNA sequencing was performed; and to analyse the density of each type of livestock that can act as intermediate host, and features of medical importance such as cyst organ location. METHODS: Literature search in numerous databases. We included only articles where samples were genotyped by sequencing since to date it is the most accurate method to unambiguously identify all E. granulosus s. l. genotypes. Also, we report new E. granulosus s. l. samples from Argentina and Uruguay analysed by sequencing of cox1 gene. RESULTS: In South America, five countries have cystic echinococcosis cases for which sequencing data are available: Argentina, Brazil, Chile, Peru and Uruguay, adding up 1534 cases. E. granulosus s. s. (G1) accounts for most of the global burden of human and livestock cases. Also, E. canadensis (G6) plays a significant role in human cystic echinococcosis. Likewise, worldwide analysis of human cases showed that 72.9% are caused by E. granulosus s. s. (G1) and 12.2% and 9.6% by E. canadensis G6 and G7, respectively. CONCLUSIONS: E. granulosus s. s. (G1) accounts for most of the global burden followed by E. canadensis (G6 and G7) in South America and worldwide. This information should be taken into account to suit local cystic echinococcosis control and prevention programmes according to each molecular epidemiological situation.

microRNA profiling in the zoonotic parasite Echinococcus canadensis using a high-throughput approach.

BACKGROUND: microRNAs (miRNAs), a class of small non-coding RNAs, are key regulators of gene expression at post-transcriptional level and play essential roles in fundamental biological processes such as development and metabolism. The particular developmental and metabolic characteristics of cestode parasites highlight the importance of studying miRNA gene regulation in these organisms. Here, we perform a comprehensive analysis of miRNAs in the parasitic cestode Echinococcus canadensis G7, one of the causative agents of the neglected zoonotic disease cystic echinococcosis. METHODS: Small RNA libraries from protoscoleces and cyst walls of E. canadensis G7 and protoscoleces of E. granulosus sensu stricto G1 were sequenced using Illumina technology. For miRNA prediction, miRDeep2 core algorithm was used. The output list of candidate precursors was manually curated to generate a high confidence set of miRNAs. Differential expression analysis of miRNAs between stages or species was estimated with DESeq. Expression levels of selected miRNAs were validated using poly-A RT-qPCR. RESULTS: In this study we used a high-throughput approach and found transcriptional evidence of 37 miRNAs thus expanding the miRNA repertoire of E. canadensis G7. Differential expression analysis showed highly regulated miRNAs between life cycle stages, suggesting a role in maintaining the features of each developmental stage or in the regulation of developmental timing. In this work we characterize conserved and novel Echinococcus miRNAs which represent 30 unique miRNA families. Here we confirmed the remarkable loss of conserved miRNA families in E. canadensis, reflecting their low morphological complexity and high adaptation to parasitism. CONCLUSIONS: We performed the first in-depth study profiling of small RNAs in the zoonotic parasite E. canadensis G7. We found that miRNAs are the preponderant small RNA silencing molecules, suggesting that these small RNAs could be an essential mechanism of gene regulation in this species. We also identified both parasite specific and divergent miRNAs which are potential biomarkers of infection. This study will provide valuable information for better understanding of the complex biology of this parasite and could help to find new potential targets for therapy and/or diagnosis.

Sequencing, bioinformatic characterization and expression pattern of a putative amino acid transporter from the parasitic cestode Echinococcus granulosus.

We have sequenced and partially characterized an Echinococcus granulosus cDNA, termed egat1, from a protoscolex signal sequence trap (SST) cDNA library. The isolated 1627 bp long cDNA contains an ORF of 489 amino acids and shows an amino acid identity of 30% with neutral and excitatory amino acid transporters members of the Dicarboxylate/Amino Acid Na+ and/or H+ Cation Symporter family (DAACS) (TC 2.A.23). Additional bioinformatics analysis of EgAT1, confirmed the results obtained by similarity searches and showed the presence of 9 to 10 transmembrane domains, consensus sequences for N-glycosylation between the third and fourth transmembrane domain, a highly similar hydropathy profile with ASCT1 (a known member of DAACS family), high score with SDF (Sodium Dicarboxilate Family) and similar motifs with EDTRANSPORT, a fingerprint of excitatory amino acid transporters. The localization of the putative amino acid transporter was analyzed by in situ hybridization and immunofluorescence in protoscoleces and associated germinal layer. The in situ hybridization labelling indicates the distribution of egat1 mRNA throughout the tegument. EgAT1 protein, which showed in Western blots a molecular mass of approximately 60 kD, is localized in the subtegumental region of the metacestode, particularly around suckers and rostellum of protoscoleces and layers from brood capsules. The sequence and expression analyses of EgAT1 pave the way for functional analysis of amino acids transporters of E. granulosus and its evaluation as new drug targets against cystic echinococcosis.

Echinococcus granulosus antigen B gene family: further studies of strain polymorphism at the genomic and transcriptional levels.

Echinococcus granulosus AgB gene family is constituted by five gene loci. In a previous study, we analyzed the strain variation of EgAgB2/B4 sequences. Here, we have analyzed, by SSCP and sequencing, 250 genomic clones of EgAgB1/B3/B5 gene cluster from five E. granulosus strains. Several new EgAgB genomic variants were found. EgAgB1 and EgAgB3 genomic sequences grouped E. granulosus strains by phylogenetic tools in two clusters: one formed by G1/G2 and the other by G5, G6/G7 strains, in accordance with other molecular markers. EgAgB5 genomic and cDNA sequences were only found in G1/G2 cluster. Reverse transcription-PCR analysis using subunit specific primers revealed that all the EgAgB genes were transcribed in G1 and G7 strains with the exception of EgAgB5 transcripts that were not detected in G7 strain. Interestingly, AgB2 transcripts that were probably processed by an aberrant splicing mechanism leading to a non-functional B2 protein were found in G7 strain.

Identification and intra-specific variability analysis of secreted and membrane-bound proteins from Echinococcus granulosus.

Echinococcus granulosus, the etiological agent of cystic hydatid disease, exists as a series of strains or genotypes, differing in biological features. Many of the secreted and membrane-bound proteins (S/M) from helminth parasites are involved in the host-parasite interplay and constitute potential targets for diagnosis, anti-parasitic drugs and vaccines. A number of E. granulosus S/M proteins were identified using the signal sequence trap technique. Six out of seven cDNA fragments of these newly identified proteins showed nucleotide and amino acid sequence variation. Inter-strain variation was reported for other characterized S/M proteins as the vaccine target EG95 and the major hydatid cyst fluid antigen, Antigen B (AgB). AgB is highly polymorphic, 101 different sequences related to AgB were reported so far and were grouped in 5 genes (EgB1-EgB5) and one pseudogene (EgB2p) exclusive of G5, G6/G7 genotypes. The significance of AgB polymorphism and possible consequences in diagnostic performance are discussed. The diagnostic value of the new protein variants detected in E. granulosus strains could be determined through standardized inter-laboratory studies as the recently done by the South American Network for Hydatid Serology.

Comparative analysis of the diagnostic performance of six major Echinococcus granulosus antigens assessed in a double-blind, randomized multicenter study.

The serodiagnosis of hydatid disease is a valuable instrument for clinical diagnosis and epidemiological surveillance of high-risk populations. In the past decade a wealth of reports on the diagnostic performance of numerous antigens have been produced. However, their diagnostic value has been estimated under different conditions, using different serum collection, therefore precluding their direct comparison. Here we report an unbiased comparison of the same batch of six major E. granulosus antigens, namely, hydatid cyst fluid (HCF), native antigen B (AgB), two recombinant AgB subunits, an AgB-derived synthetic peptide, and recombinant cytosolic malate dehydrogenase from E. granulosus (EgMDH), against the same serum collection. The double-blind analysis was performed using a standardized protocol and receiver operating characteristic (ROC) data analysis by a network of six South American laboratories. High intercenter reproducibility was attained, and the intralaboratory analysis allowed the comparative ranking of the antigen panel. HCF, AgB, and its AgB8/1 subunit exhibited equivalent diagnostic efficiencies, 81.4% +/- 0.5%, 81.3% +/- 0.6%, and 81.9% +/- 2.0%, respectively; with a more favorable balance toward specificity in the case of the last antigen. The diagnostic efficiencies for the other three antigens were 76.8% +/- 6.8%, 69.1% +/- 2.7%, and 66.8% +/- 2.1%, for the peptide, the AgB8/2 subunit, and the EgMDH, respectively. The study also included an analysis of batch-to-batch variation in the diagnostic performance of different HCF regional preparations. Based on these results, a suggested recommendation on the use of these antigens was drawn.

Cystic echinococcosis in Argentina: evolution of metacestode and clinical expression in various Echinococcus granulosus strains.

Echinococcus granulosus hydatid cysts were examined in 41 patients from Neuquén and Tucumán provinces in Argentina. Sequencing of the mitochondrial cytochrome c oxidase subunit 1 (CO1) revealed in 19 patients common sheep strain (G1), in 6 patients Tasmania sheep strain (G2), in 1 patient cattle strain (G5), and in 15 patients camel strain (G6). In Argentina the only known is the domestic cycle that affects dogs and herbivorous, including ovine, swine, cattle and goats. These strains produced a total of 58.6% of primary liver infections, 29.2% primary in lung, 2.4% primary in spleen and 9.8% were multiorgan abdominal infections. The metacestode was classified using the evolutive stages proposed by WHO-IWGE (from CE1 to CE5). We estimated that CE1 cyst has a duration of about 22 years, CE2 of 14 years, CE3 of 10 years, CE4 of 19 years and CE5 was not determined. The active types CE1 and CE2 reached 75% of all cases from all strains. In 36 patients with cysts from G1, G5 and G6 strain, there were only two asymptomatic cases. The strains of the E. granulosus complex do not present important clinical differences; only G6 seems to have higher growth rate.

Several strains of Echinococcus granulosus infect livestock and humans in Argentina.

Mitochondrial cytochrome oxidase subunit 1 (CO1) sequencing, Southern blot of a repetitive DNA element and single strand conformation polymorphism of the 5' non-transcribed region of the cytosolic malate dehydrogenase (MDH) gene were used to determine the extent and distribution of Echinococcus granulosus genetic variation in Argentina. Five distinct strains of E. granulosus were shown to exist in the country. The common sheep, Tasmanian sheep, cattle and camel strains were identified in humans. Unlike the situation found in other countries, where the common sheep strain is the major source of human contamination, the Tasmanian sheep and camel strains produced a significant number of human infections in some regions of Argentina. This is the first report of cattle strain in humans in South America. Goats could be the natural intermediate host of the camel strain, which was not identified in humans from other regions so far. More than one genotype was identified in the same geographic area. These findings may have important consequences for human health and the control of hydatid disease. Within-strain differences were also observed, showing the potential of variation of E. granulosus.