Assessment of Echinococcus granulosus polymorphism in Qinghai Province, People’s Republic of China

Update on the genetic diversity and population structure of Echinococcus granulosus in Gansu Province, Tibet Autonomous Region, and Xinjiang Uygur Autonomous Region, Western China, inferred from mitochondrial cox1, nad1, and nad5 sequences

The identification of additional Echinococcus granulosus sensu lato (s.l.) complex species/genotypes in recent years raises the possibility that there might be more variation among this species in China than is currently understood. The aim of this study was to explore intra- and inter-species variation and population structure of Echinococcus species isolated from sheep in three areas of Western China. Of the isolates, 317, 322, and 326 were successfully amplified and sequenced for cox1, nad1, and nad5 genes, respectively. BLAST analysis revealed that the majority of the isolates were E. granulosus s.s., and using the cox1, nad1, and nad5 genes, respectively, 17, 14, and 11 isolates corresponded to Elodea canadensis (genotype G6/G7). In the three study areas, G1 genotypes were the most prevalent. There were 233 mutation sites along with 129 parsimony informative sites. A transition/transversion ratio of 7.5, 8, and 3.25, respectively, for cox1, nad1, and nad5 genes was obtained. Every mitochondrial gene had intraspecific variations, which were represented in a star-like network with a major haplotype with observable mutations from other distant and minor haplotypes. The Tajima's D value was significantly negative in all populations, indicating a substantial divergence from neutrality and supporting the demographic expansion of E. granulosus s.s. in the study areas. The phylogeny inferred by the maximum likelihood (ML) method using nucleotide sequences of cox1-nad1-nad5 further confirmed their identity. The nodes assigned to the G1, G3, and G6 clades as well as the reference sequences utilized had maximal posterior probability values (1.00). In conclusion, our study confirms the existence of a significant major haplotype of E. granulosus s.s. where G1 is the predominant genotype causing of CE in both livestock and humans in China.

Genetic variation of Echinococcus spp. in yaks and sheep in the Tibet Autonomous Region of China based on mitochondrial DNA

Background

Cystic echinococcosis (CE) in humans and livestock is caused by Echinococcus granulosus (sensu lato). In China where CE is endemic, a number of studies have shown that Echinococcus granulosus (sensu stricto) is majorly responsible for CE. However, E. canadensis (G6) which is the second leading cause of CE is now being detected in most parts of the country. In this study, the species diversity and genetic variation of Echinococcus granulosus (s.l.) in four counties in Tibet Autonomous Region of China were investigated.

Methods

Infection with Echinococcus granulosus (s.s.) in yaks and sheep was identified using NADH dehydrogenase subunit 1 and 5 (nad1 and nad5) mitochondrial genes while the genotype G6 of E. canadensis initially diagnosed with NADH dehydrogenase subunit 1 (nad1) was further confirmed by analysis of the complete mitochondrial genome and a phylogenetic network constructed based on the nad2 and nad5 genes.

Results

Out of 85 hydatid cyst samples collected from slaughtered sheep (n = 54) and yaks (n = 31), 83 were identified as E. granulosus (s.s.) G1 (n = 77), G3 (n = 6) and 2 were identified as E. canadensis G6. Analysis of the nad1/nad5 genes revealed 16/17 mutations with 9/14 parsimony informative sites resulting in 15/14 haplotypes, respectively. Haplotype diversity (Hd) and nucleotide diversity (π) of E. granulosus (s.s.) population were 0.650 and 0.00127 for nad1 and 0.782 and 0.00306 for nad5, respectively, with an overall negative Tajima’s D and Fu’s Fs. A low F_ST indicated no genetic difference between isolates from sheep and yaks.

Conclusion

Pockets of infection with E. canadensis (G6, G7, G8 and G10) have been previously reported in sheep, goats, yaks and/or humans in different parts of China. While the G6 genotype has been previously reported in sheep in the Tibet Autonomous Region, the detection in a yak in the present study represents the first to the best of our knowledge. Therefore, we recommend future surveys and control efforts to comprehensively investigate other potential intermediate hosts for the prevalence and genetic diversity of the E. canadensis group (G6, G7, G8 and G10) across the country and their inclusion into the existing CE control programme.

Genetic characterization of Echinococcus isolates from various intermediate hosts in the Qinghai-Tibetan Plateau Area, China

This study examined Echinococcus spp. genotypes and genetic variants isolated from humans as well as domestic and wild animals from the Qinghai-Tibetan Plateau Area using the cox1 gene. All samples except the pika isolates were identified as the Echinococcus granulosus sensu stricto. Sixteen different haplotypes with considerable intraspecific variation were detected and characterized in mitochondrial cox1 sequences. The parsimonious network of cox1 haplotypes showed star-like features, and the neutrality indexes computed via Tajima's D and Fu's Fs tests showed high negative values in E. granulosus s. s., indicating deviations from neutrality; the Fst values were low among the populations, implying that the populations were not genetically differentiated. The pika isolates were identified as E. multilocularis and E. shiquicus. Only one haplotype was recognized in the pika isolates. E. granulosus s. s. was the predominant species found in animals and humans, followed by E. multilocularis and E. shiquicus, with high genetic diversity circulating among the animals and humans in this area. Further studies are needed to cover many sample collection sites and larger numbers of pathogen isolates, which may reveal abundant strains and/or other haplotypes in the hydatid cysts infecting human and animal populations of the QTPA, China.

Echinococcosis transmission on the Tibetan Plateau

Since the mid-1990s detailed studies and field investigations on the Tibetan Plateau have revealed human echinococcosis to be an under-reported major public health problem, particularly in the dominant pastoral communities in the eastern and central regions. Human prevalence surveys showed that cystic echinococcosis (CE, caused by Echinococcus granulosus) and alveolar echinococcosis (AE, caused by Echinococcus multilocularis) are co-endemic with higher burdens of each disease than other endemic world regions. Epidemiological investigations identified some major risk factors for human CE and AE including dog ownership, husbandry practices and landscape features. Dogs appear to be the major zoonotic reservoir for both E. granulosus and E. multilocularis, but the latter is also transmitted in complex wildlife cycles. Small mammal assemblages especially of vole and pika species thrive on the Plateau and contribute to patterns of E. multilocularis transmission which are influenced by landscape characteristics and anthropogenic factors. Tibetan foxes are a principal definitive host for both E. multilocularis and E. shiquicus. In 2006 a national echinococcosis control programme was initiated in Tibetan communities in northwest Sichuan Province and rolled out to all of western China by 2010, and included improved surveillance (and treatment access) of human disease and regular deworming of dogs with annual copro-testing. Control of echinococcosis in Tibetan pastoral communities poses a difficult challenge for delivery and sustainability.

Mitochondrial genome data confirm that yaks can serve as the intermediate host of Echinococcus canadensis (G10) on the Tibetan Plateau

Background

Cervids used to be considered the only animal intermediate hosts of the G10 genotype of Echinococcus canadensis. Yaks are often herded in the Qinghai-Tibet Plateau, China, where echinococcosis remains prevalent. However, no E. canadensis G10 cases have been recorded in yaks until now. The aim of our study was to identify causative agents of echinococcosis in yaks in this region.

Methods

Total genomic DNA was extracted from the germinal layer of one hydatid using a Blood and Tissue Kit. Full-length mitochondrial (mt) cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) genes were amplified by PCR. All purified PCR products were directly sequenced in both directions. Then seven pairs of overlap primers were designed to amplify the entire mt genome sequence of a suspected E. canadensis G10 isolate. Phylogenetic analyses were performed based on concatenated nucleotides from the 12 protein-coding genes of mt genomes of Echinococcus species in a Bayesian framework using MrBayes v3.1 and implementing the GTR + I + G model.

Results

Hydatids were found in yaks (n = 129) when organs were inspected at the slaughterhouse in Maqu county, Gannan Tibetan Autonomous Prefecture, Gansu Province, China in October 2016. Of these, 33 (25.6%) harbored up to a dozen hydatid cysts. One cyst from each yak was characterized by sequencing its mitochondrial (mt) cox1 and nad1 genes. On the basis of these sequence data, 32 cysts were identified as Echinococcus granulosus (sensu stricto) (G1-G3) and the remaining one was identified as the G10 genotype of E. canadensis. Its mt genome was then fully sequenced and compared with that of the G10 genotype in GenBank (AB745463). Phylogenetic analysis using complete mt genomes confirmed the Chinese cyst as belonging to the G10 genotype.

Conclusions

To our knowledge, this is the first report globally of E. canadensis (G10) from yaks in China, which suggests that the G10 genotype has a wider geographical distribution and broader host range than previously believed. This genotype has therefore potential risks to human health and animal husbandry.

Global Distribution of Alveolar and Cystic Echinococcosis

Alveolar echinococcosis (AE) and cystic echinococcosis (CE) are severe helminthic zoonoses. Echinococcus multilocularis (causative agent of AE) is widely distributed in the northern hemisphere where it is typically maintained in a wild animal cycle including canids as definitive hosts and rodents as intermediate hosts. The species Echinococcus granulosus, Echinococcus ortleppi, Echinococcus canadensis and Echinococcus intermedius are the causative agents of CE with a worldwide distribution and a highly variable human disease burden in the different endemic areas depending upon human behavioural risk factors, the diversity and ecology of animal host assemblages and the genetic diversity within Echinococcus species which differ in their zoonotic potential and pathogenicity. Both AE and CE are regarded as neglected zoonoses, with a higher overall burden of disease for CE due to its global distribution and high regional prevalence, but a higher pathogenicity and case fatality rate for AE, especially in Asia. Over the past two decades, numerous studies have addressed the epidemiology and distribution of these Echinococcus species worldwide, resulting in better-defined boundaries of the endemic areas. This chapter presents the global distribution of Echinococcus species and human AE and CE in maps and summarizes the global data on host assemblages, transmission, prevalence in animal definitive hosts, incidence in people and molecular epidemiology.

Ecology and Life Cycle Patterns of Echinococcus Species

The genus Echinococcus is composed of eight generally recognized species and one genotypic cluster (Echinococcus canadensis cluster) that may in future be resolved into one to three species. For each species, we review existing information on transmission routes and life cycles in different geographical contexts and - where available - include basic biological information of parasites and hosts (e.g., susceptibility of host species). While some Echinococcus spp. are transmitted in life cycles that involve predominantly domestic animals (e.g., dog - livestock cycles), others are wildlife parasites that do or do not interact with domestic transmission. In many cases, life cycle patterns of the same parasite species differ according to geography. Simple life cycles contrast with transmission patterns that are highly complex, involving multihost systems that may include both domestic and wild mammals. Wildlife transmission may be primary or secondary, i.e., resulting from spillovers from domestic animals. For most of the species and regions, existing information does not yet permit a conclusive description of transmission systems. Such data, however, would be highly relevant, e.g., for anticipation of geographical changes of the presence and frequency of these parasites in a warming world, or for initiating evidence-based control strategies.

Canine echinococcosis: genetic diversity of Echinococcus granulosus sensu stricto (s.s.) from definitive hosts

Canids, particularly dogs, constitute the major source of cystic echinococcosis (CE) infection to humans, with the majority of cases being caused by Echinococcus granulosus (G1 genotype). Canine echinococcosis is an asymptomatic disease caused by adult tapeworms of E. granulosus sensu lato (s.l.). Information on the population structure and genetic variation of adult E. granulosus is limited. Using sequenced data of the mitochondrial cytochrome c oxidase subunit 1 (cox1) we examined the genetic diversity and population structure of adult tapeworms of E. granulosus (G1 genotype) from canid definitive hosts originating from various geographical regions and compared it to that reported for the larval metacestode stage from sheep and human hosts. Echinococcus granulosus (s.s) was identified from adult tapeworm isolates from Kenya, Libya, Tunisia, Australia, China, Kazakhstan, United Kingdom and Peru, including the first known molecular confirmation from Gaza and the Falkland Islands. Haplotype analysis showed a star-shaped network with a centrally positioned common haplotype previously described for the metacestode stage from sheep and humans, and the neutrality indices indicated population expansion. Low Fst values suggested that populations of adult E. granulosus were not genetically differentiated. Haplotype and nucleotide diversities for E. granulosus isolates from sheep and human origin were twice as high as those reported from canid hosts. This may be related to self-fertilization of E. granulosus and/or to the longevity of the parasite in the respective intermediate and definitive hosts. Improved nuclear single loci are required to investigate the discrepancies in genetic variation seen in this study.

Epidemiology and control of echinococcosis in central Asia, with particular reference to the People's Republic of China

At least 270 million people (58% of the total population) are at risk of cystic echinococcosis (CE) in Central Asia including areas of Mongolia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, Afghanistan, Iran, Pakistan and western China. The annual surgical incidence rate in Uzbekistan and Tadjikistan has been estimated to be as high as 25-27 cases/100,000 with the highest prevalence reaching 10% (range from 0.8 to 11.9%) in some Tibetan communities in western China. Echinococcus transmission in the region is largely associated with social factors including limited community knowledge of echinococcosis, small-scale household animal production, home killing of livestock, and the feeding of dogs with uncooked offal. Alveolar echinococcosis (AE) is also endemic in Central Asia and is recognized as a major problem in some Tibetan communities with up to 6% of villagers infected in some villages. In western China, 5-30% of the population are seropositive against E. granulosus antigens, indicating that a large number of individuals have been exposed to the parasite. Although echinococcosis control programs have been initiated in some countries in Central Asia, control efforts are generally fragmented and uncoordinated. Monthly deworming of dogs with praziquantel (PZQ), as a key measure to control the Echinococcus parasites, has been used in western China. However, the approach has proven difficult in local semi-nomadic communities. Additional control measures including health education, domestic livestock animal treatment/vaccination and dog vaccination are needed in CE-endemic areas to accelerate progress.

Transcriptome profiles of the protoscoleces of Echinococcus granulosus reveal that excretory-secretory products are essential to metabolic adaptation

Background

Cystic hydatid disease (CHD) is caused by the larval stages of the cestode and affects humans and domestic animals worldwide. Protoscoleces (PSCs) are one component of the larval stages that can interact with both definitive and intermediate hosts. Previous genomic and transcriptomic data have provided an overall snapshot of the genomics of the growth and development of this parasite. However, our understanding of how PSCs subvert the immune response of hosts and maintains metabolic adaptation remains unclear. In this study, we used Roche 454 sequencing technology and in silico secretome analysis to explore the transcriptome profiles of the PSCs from E. granulosus and elucidate the potential functions of the excretory-secretory proteins (ESPs) released by the parasite.

Methodology/Principal Findings

A large number of nonredundant sequences as unigenes were generated (26,514), of which 22,910 (86.4%) were mapped to the newly published E. granulosus genome and 17,705 (66.8%) were distributed within the coding sequence (CDS) regions. Of the 2,280 ESPs predicted from the transcriptome, 138 ESPs were inferred to be involved in the metabolism of carbohydrates, while 124 ESPs were inferred to be involved in the metabolism of protein. Eleven ESPs were identified as intracellular enzymes that regulate glycolysis/gluconeogenesis (GL/GN) pathways, while a further 44 antigenic proteins, 25 molecular chaperones and four proteases were highly represented. Many proteins were also found to be significantly enriched in development-related signaling pathways, such as the TGF-β receptor pathways and insulin pathways.

Conclusions/Significance

This study provides valuable information on the metabolic adaptation of parasites to their hosts that can be used to aid the development of novel intervention targets for hydatid treatment and control.

The successful infection establishment of parasites depends on their ability to combat their host's immune system while maintaining metabolic adaptation to their hosts. The mechanisms of these processes are not well understood. We used the protoscoleces (PSCs) of E. granulosus as a model system to study this complex host-parasite interaction by investigating the role of excretory-secretory proteins (ESPs) in the physiological adaptation of the parasite. Using Roche 454 sequencing technology and in silico secretome analysis, we predicted 2280 ESPs and analyzed their biological functions. Our analysis of the bioinformatic data suggested that ESPs are integral to the metabolism of carbohydrates and proteins within the parasite and/or hosts. We also found that ESPs are involved in mediating the immune responses of hosts and function within key development-related signaling pathways. We found 11 intracellular enzymes, 25 molecular chaperones and four proteases that were highly represented in the ESPs, in addition to 44 antigenic proteins that showed promise as candidates for vaccine or serodiagnostic development purposes. These findings provide valuable information on the mechanisms of metabolic adaptation in parasites that will aid the development of novel hydatid treatment and control targets.

Genetic characterization of human-derived hydatid cysts of Echinococcus granulosus sensu lato in Heilongjiang Province and the first report of G7 genotype of E. canadensis in humans in China

Cystic echinococcosis (CE) caused by the larval stage of Echinococcus granulosus sensu lato (s.l.) is one of the most important zoonotic parasitic diseases worldwide and 10 genotypes (G1–G10) have been reported. In China, almost all the epidemiological and genotyping studies of E. granulosus s.l. are from the west and northwest pasturing areas. However, in Heilongjiang Province of northeastern China, no molecular information is available on E. granulosus s.l. To understand and to speculate on possible transmission patterns of E. granulosus s.l., we molecularly identified and genotyped 10 hydatid cysts from hepatic CE patients in Heilongjiang Province based on mitochondrial cytochrome c oxidase subunit I (cox1), cytochrome b (cytb) and NADH dehydrogenase subunit 1 (nad1) genes. Two genotypes were identified, G1 genotype (n = 6) and G7 genotype (n = 4). All the six G1 genotype isolates were identical to each other at the cox1 locus; three and two different sequences were obtained at the cytb and nad1 loci, respectively, with two cytb gene sequences not being described previously. G7 genotype isolates were identical to each other at the cox1, cytb and nad1 loci; however, the cytb gene sequence was not described previously. This is the first report of G7 genotype in humans in China. Three new cytb gene sequences from G1 and G7 genotypes might reflect endemic genetic characterizations. Pigs might be the main intermediate hosts of G7 genotype in our investigated area by homology analysis. The results will aid in making more effective control strategies for the prevention of transmission of E. granulosus s.l.

Molecular characterization and sequence analysis of Echinococcus granulosus from sheep isolates in East Azerbaijan province, northwest of Iran

Echinococcus granulosus as an etiologic agent of hydatid cyst is one of the most important zoonotic helminthes in the world that causing enormous economic and health losses. The aim of this study was to evaluate genotype of E. granulosus isolated from sheep using mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and sequencing method in East Azerbaijan province, northwest of Iran. Nineteen sheep hydatid cyst samples were collected. Genomic DNA was extracted from protoscoleces using commercial DNA extraction kit. Mitochondrial cox1 region was amplified by polymerase chain reaction (PCR) and all isolates were sequenced. Afterward, sequences were analyzed for determination of genotypes by related software. G1 (94.73 %) and G3 (5.27 %) genotypes were identified from the isolates which out of 19 hydatid cysts, 17 samples were G1B, 1 sample G1D and the other one had G3 genotype. Results of this study indicate that common sheep strain (G1); especially G1B is the dominant subtype of E. granulosus in East Azerbaijan province.

Sequence analysis of cytb gene in Echinococcus granulosus from Western China

Echinococcus granulosus is the causative agent of cystic echinococcosis with medical and veterinary importance in China. Our main objective was to discuss the genotypes and genetic diversity of E. granulosus present in domestic animals and humans in western China. A total of 45 hydatid cyst samples were collected from sheep, humans, and a yak and subjected to an analysis of the sequences of mitochondrial cytochrome b (cytb) gene. The amplified PCR product for all samples was a 1,068 bp band. The phylogenetic analysis showed that all 45 samples were identified as E. granulosus (genotype G1). Ten haplotypes were detected among the samples, with the main haplotype being H1. The haplotype diversity was 0.626, while the nucleotide diversity was 0.001. These results suggested that genetic diversity was low among our samples collected from the west of China based on cytb gene analysis. These findings may provide more information on molecular characteristics of E. granulosus from this Chinese region.

Genetic diversity of Echinococcus granulosus in southwest China determined by the mitochondrial NADH dehydrogenase subunit 2 gene

We evaluated genetic diversity and structure of Echinococcus granulosus by analyzing the complete mitochondrial NADH dehydrogenase subunit 2 (ND2) gene in 51 isolates of E. granulosus sensu stricto metacestodes collected at three locations in this region. We detected 19 haplotypes, which formed a distinct clade with the standard sheep strain (G1). Hence, all 51 isolates were identified as E. granulosus sensu stricto (G1–G3). Genetic relationships among haplotypes were not associated with geographical divisions, and fixation indices (Fst) among sampling localities were low. Hence, regional populations of E. granulosus in the southwest China are not differentiated, as gene flow among them remains high. This information is important for formulating unified region-wide prevention and control measures. We found large negative Fu's Fs and Tajima's D values and a unimodal mismatch distribution, indicating that the population has undergone a demographic expansion. We observed high genetic diversity among the E. granulosus s. s. isolates, indicating that the parasite population in this important bioregion is genetically robust and likely to survive and spread. The data from this study will prove valuable for future studies focusing on improving diagnosis and prevention methods and developing robust control strategies.

Canine echinococcosis: global epidemiology and genotypic diversity

Canine echinococcosis is a potential zoonotic infection caused by the adult form of several cestode species belonging to the genus Echinococcus, of which E. granulosus sensu lato and E. multilocularis are the most epidemiologically relevant. Dogs infected with E. granulosus and E. multilocularis are widely regarded as the main source of infection for human cystic and alveolar echinococcosis, diseases that cause substantial morbidity and socio-economic burden in several regions of the world. Following our previous review on the global situation of cystic echinococcosis in livestock species (Cardona and Carmena. Vet. Parasitol. 2013;192:10-32), we summarize here current knowledge on the global epidemiology, geographical distribution and molecular diversity of Echinococcus spp. infection in dogs. We address relevant topics including the implications of the increasing urbanization of wildlife species such as foxes, coyotes, and dingoes in the establishment of urban cycles of Echinococcus spp., or the rising concerns regarding the role of unsupervised translocation of infected dogs in spreading the infection to Echinococcus-free areas. The involvement of wildlife species as natural reservoirs of disease to domestic animals and humans and the epidemiological significance of the sympatric occurrence of different Echinococcus species in the same geographical region are also debated. Data presented are expected to be useful for policy makers, educational and health authorities responsible for designing and implementing effective measures for disease control and prevention.

Echinococcus granulosus sensu lato genotypes infecting humans--review of current knowledge

Genetic variability in the species group Echinococcus granulosus sensu lato is well recognised as affecting intermediate host susceptibility and other biological features of the parasites. Molecular methods have allowed discrimination of different genotypes (G1-10 and the 'lion strain'), some of which are now considered separate species. An accumulation of genotypic analyses undertaken on parasite isolates from human cases of cystic echinococcosis provides the basis upon which an assessment is made here of the relative contribution of the different genotypes to human disease. The allocation of samples to G-numbers becomes increasingly difficult, because much more variability than previously recognised exists in the genotypic clusters G1-3 (=E. granulosus sensu stricto) and G6-10 (Echinococcus canadensis). To accommodate the heterogeneous criteria used for genotyping in the literature, we restrict ourselves to differentiate between E. granulosus sensu stricto (G1-3), Echinococcus equinus (G4), Echinococcus ortleppi (G5) and E. canadensis (G6-7, G8, G10). The genotype G1 is responsible for the great majority of human cystic echinococcosis worldwide (88.44%), has the most cosmopolitan distribution and is often associated with transmission via sheep as intermediate hosts. The closely related genotypes G6 and G7 cause a significant number of human infections (11.07%). The genotype G6 was found to be responsible for 7.34% of infections worldwide. This strain is known from Africa and Asia, where it is transmitted mainly by camels (and goats), and South America, where it appears to be mainly transmitted by goats. The G7 genotype has been responsible for 3.73% of human cases of cystic echinococcosis in eastern European countries, where the parasite is transmitted by pigs. Some of the samples (11) could not be identified with a single specific genotype belonging to E. canadensis (G6/10). Rare cases of human cystic echinococcosis have been identified as having been caused by the G5, G8 and G10 genotypes. No cases of human infection with G4 have been described. Biological differences between the species and genotypes have potential to affect the transmission dynamics of the parasite, requiring modification of methods used in disease control initiatives. Recent investigations have revealed that the protective vaccine antigen (EG95), developed for the G1 genotype, is immunologically different in the G6 genotype. Further research will be required to determine whether the current EG95 vaccine would be effective against the G6 or G7 genotypes, or whether it will be necessary, and possible, to develop genotype-specific vaccines.

Proteomic characterization of larval and adult developmental stages in Echinococcus granulosus reveals novel insight into host-parasite interactions

Cystic hydatid disease is an important zoonosis caused by Echinococcus granulosus infection. The expression profiles of its parasitic life stages and host-Echinococcus interactions remain to be elucidated. Here, we identified 157 adult and 1588 protoscolex proteins (1610 in all), including 1290 novel identifications. Paramyosins and an antigen B (AgB) were the dominant adult proteins. Dog proteins (30) identified in adults indicated diminished local inflammation caused by adult infection. The protoscolex expresses proteins that have been reported to be antigens in other parasites, such as 6-phosphofructokinase and calcineurin B. Pathway analyses suggested that E. granulosus uses both aerobic and anaerobic carbohydrate metabolisms to generate ATP. E. granulosus expresses proteins involved in synthesis and metabolism of lipids or steroids. At least 339 of 390 sheep proteins identified in protoscolex were novel identifications not seen in previous analyses. IgGs and lambda light chains were the most abundant antibody species. Sheep proteins were enriched for detoxification pathways, implying that host detoxification effects play a central role during host-parasite interactions. Our study provides valuable data on E. granulosus expression characteristics, allowing novel insights into the molecular mechanisms involved in host-parasite interactions.

BIOLOGICAL SIGNIFICANCE

In this study, the Echinococcus granulosus adult worm proteome was analyzed for the first time. The protein identification of E. granulosus protoscoleces was extended dramatically. We also identified the most abundant host proteins co-purified with Echinococcus. The results provide useful information pertaining to the molecular mechanisms behind host-Echinococcus interaction and Echinococcus biology. This data also increases the potential for identifying vaccine candidates and new therapeutic targets, and may aid in the development of protein probes for selective and sensitive diagnosis of echinococcosis infection. In addition, the data collected here represents a valuable proteomic resource for subsequent genome annotation.

Enhanced bioavailability and cysticidal effect of three mebendazole-oil preparations in mice infected with secondary cysts of Echinococcus granulosus

The aim of the present study is to explore the possibility to increase the efficacy of mebendazole (MBZ) against secondary cysts of Echinococcus granulosus harbored in mice by augmenting the solubility and bioavailability of the drug. Firstly, the saturated solubility of MBZ in nine kinds of oil was determined by high performance liquid chromatography (HPLC), and MBZ was found exhibiting the highest, secondary, and lowest solubility in oleic acid (OA), glycerol trioleate (GT), and soybean oil (SB), respectively. Secondly, MBZ-OA suspension, MBZ-GT suspension, MBZ-SB suspension, and MBZ suspended in 1 % tragacanth (MBZ-1 % tragacanth) were selected for further studies on pharmacokinetics and experimental therapy in mice. Four groups of mice were treated orally with one of aforementioned four MBZ preparations at a single dose of 25 mg/kg, and concentrations of MBZ in plasma obtained from each mouse at various intervals within 24 h postadministration were determined by HPLC. The major pharmacokinetic parameters calculated by MBZ plasma concentration-time curve demonstrated that the peak concentration of the drug (C (max) ) values obtained from three MBZ-oil preparation groups was 1.6-2.8 times higher than that of MBZ-1 % tragacanth group. The same was true that the area under the drug concentration-time curve (AUC(0-∞)) values of 19.8 (2.5)-28.2 (2.5) μg/ml × h revealed in the three MBZ-oil preparation groups was significantly higher than that of 11.6 (2.0) μg/ml × h in MBZ-1 % tragacanth group, and the bioavailability of the three MBZ-oil preparation groups was 71-143 % higher than that of MBZ-1 % tragacanth group. In mice infected with secondary cysts of E. granulosus for 8 months treated orally with MBZ-1 % tragacanth at a daily dose of 25 mg/kg for 14 consecutive days, the mean cyst weight was lower than that of untreated control, but the difference was not statistically significant with cyst weight reduction of 48 %. When the infected mice received three MBZ-oil preparations at the same oral dose schedule as aforementioned, the mean cyst weights were significantly lower than those in MBZ-1 % tragacanth group or control group with cyst weight reductions of 71.2-84.7 %. The results indicate that the solubility of MBZ in oils may increase to various degrees according to the kinds of oil used. Meanwhile, three MBZ-oil (OA, GT, and SB) preparations administered orally to mice not only improve the bioavailability of MBZ relative to that of MBZ suspended in 1 % tragacanth, but their effects against hydatid cysts also significantly enhance.

Characterization of the eg95 gene family in the G6 genotype of Echinococcus granulosus

Cystic echinococcosis in humans and livestock animals is caused by infection with the cestode parasite Echinococcus granulosus. A number of genotypes of the parasite (designated G1-G10) are known to exist, with the genotype cluster G1-G3 and genotype G6 being responsible for the majority of humans infections. A recombinant vaccine has been developed for use in livestock to prevent infection with E. granulosus. The vaccine is based on the antigen EG95 which is expressed in the early larval stage (oncosphere) of the parasite. The EG95 antigen was originally cloned from the G1 genotype of E. granulosus and the protein has been found to be encoded by members of a small family of related genes in this genotype. Reliable information has not been available about the likely efficacy of the EG95 vaccine against genotypes other than G1. In this study, genomic DNA cloning techniques were used to characterize seven eg95-related gene fragments from the G6 genotype of E. granulosus. Three proteins appear to be encoded by these genes. Considerable differences were found between the EG95 related proteins from the G6 genotype compared with the EG95 protein from the G1 genotype. These differences suggest that the EG95-related proteins from the G6 genotype may have different antigenic epitopes compared with the current vaccine antigen. Data presented in this study have implications for future vaccine design and provide the information that would enable a G6 genotype-specific vaccine to be developed against E. granulosus, should this be considered a desirable addition to the available tools for control of cystic echinococcosis transmission.

Genetic polymorphisms of Echinococcus tapeworms in China as determined by mitochondrial and nuclear DNA sequences

The genetic polymorphisms of Echinococcus spp. in the eastern Tibetan Plateau and the Xinjiang Uyghur Autonomous Region were evaluated by DNA sequencing analyses of genes for mitochondrial cytochrome c oxidase subunit 1 (cox1) and nuclear elongation factor-1 alpha (ef1a). We collected 68 isolates of Echinococcus granulosus sensu stricto (s.s.) from Xinjiang and 113 isolates of E. granulosus s. s., 49 isolates of Echinococcus multilocularis and 34 isolates of Echinococcus shiquicus from the Tibetan Plateau. The results of molecular identification by mitochondrial and nuclear markers were identical, suggesting the infrequency of introgressive hybridization. A considerable intraspecific variation was detected in mitochondrial cox1 sequences. The parsimonious network of cox1 haplotypes showed star-like features in E. granulosus s. s. and E. multilocularis, but a divergent feature in E. shiquicus. The cox1 neutrality indexes computed by Tajima's D and Fu's Fs tests showed high negative values in E. granulosus s. s. and E. multilocularis, indicating significant deviations from neutrality. In contrast, the low positive values of both tests were obtained in E. shiquicus. These results suggest the following hypotheses: (i) recent founder effects arose in E. granulosus and E. multilocularis after introducing particular individuals into the endemic areas by anthropogenic movement or natural migration of host mammals, and (ii) the ancestor of E. shiquicus was segregated into the Tibetan Plateau by colonising alpine mammals and its mitochondrial locus has evolved without bottleneck effects.