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International journal for parasitology [journal]
- Geographical distribution of human Schistosoma japonicum infection in The Philippines: tools to support disease control and further elimination. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Aug 13.
Schistosoma japonicum infection is believed to be endemic in 28 of the 80 provinces of The Philippines and the most recent data on schistosomiasis prevalence have shown considerable variability between provinces. In order to increase the efficient allocation of parasitic disease control resources in the country, we aimed to describe the small-scale spatial variation in S. japonicum prevalence across The Philippines, quantify the role of the physical environment in driving the spatial variation of S. japonicum, and develop a predictive risk map of S. japonicum infection. Data on S. japonicum infection from 35,754 individuals across the country were geo-located at the barangay level and included in the analysis. The analysis was then stratified geographically for the regions of Luzon, the Visayas and Mindanao. Zero-inflated binomial Bayesian geostatistical models of S. japonicum prevalence were developed and diagnostic uncertainty was incorporated. Results of the analysis show that in the three regions, males and individuals aged ⩾ 20 years had significantly higher prevalence of S. japonicum compared with females and children < 5 years. The role of the environmental variables differed between regions of The Philippines. Schistosoma japonicum infection was widespread in the Visayas whereas it was much more focal in Luzon and Mindanao. This analysis revealed significant spatial variation in the prevalence of S. japonicum infection in The Philippines. This suggests that a spatially targeted approach to schistosomiasis interventions, including mass drug administration, is warranted. When financially possible, additional schistosomiasis surveys should be prioritized for areas identified to be at high risk but which were under-represented in our dataset.
- Genetic diversity of the Chinese liver fluke Clonorchis sinensis from Russia and Vietnam. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Aug 11.
Clonorchiasis is a parasitic disease of high public health importance in many countries in southeastern Asia and is caused by the Chinese liver fluke Clonorchis sinensis. However, the genetic structure and demographic history of its populations has not been sufficiently studied throughout the geographic range of the species and available data are based mainly on partial gene sequencing. In this study, we explored the genetic diversity of the complete 1560 bp cytochrome c oxidase subunit 1 (cox1) gene sequence for geographically isolated C. sinensis populations in Russia and Vietnam, to our knowledge for the first time. The results demonstrated low nucleotide and high haplotype differentiation within and between the two compared regions and a clear geographical vector for the distribution of genetic diversity patterns among the studied populations. These results suggest a deep local adaptation of the parasite to its environment including intermediate hosts and the existence of gene flow across the species' range. Additionally, we have predicted an amino acid substitution in the functional site of the COX1 protein among the Vietnamese populations, which were reported to be difficult to treat with praziquantel. The haplotype networks consisted of several region-specific phylogenetic lineages, the formation of which could have occurred during the most extensive penultimate glaciations in the Pleistocene Epoch. The patterns of genetic diversity and demographics are consistent with population growth of the liver fluke in the late Pleistocene following the Last Glacial Maximum, indicating the lack of a population bottleneck during the recent past in the species' history. The data obtained have important implications for understanding the phylogeography of C. sinensis, its host-parasite interactions, the ability of this parasite to evolve drug resistance, and the epidemiology of clonorchiasis under global climate change.
- Echinococcus as a model system: biology and epidemiology. [REVIEW]
- Int J Parasitol 2014 Aug 11.
The introduction of Echinococcus to Australia over 200years ago and its establishment in sheep rearing areas of the country inflicted a serious medical and economic burden on the country. This resulted in an investment in both basic and applied research aimed at learning more about the biology and life cycle of Echinococcus. This research served to illustrate the uniqueness of the parasite in terms of developmental biology and ecology, and the value of Echinococcus as a model system in a broad range of research, from fundamental biology to theoretical control systems. These studies formed the foundation for an international, diverse and ongoing research effort on the hydatid organisms encompassing stem cell biology, gene regulation, strain variation, wildlife diseases and models of transmission dynamics. We describe the development, nature and diversity of this research, and how it was initiated in Australia but subsequently has stimulated much international and collaborative research on Echinococcus.
- Proteomics informed by transcriptomics identifies novel secreted proteins in Dermacentor andersoni saliva. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Aug 7.
Dermacentor andersoni, known as the Rocky Mountain wood tick, is found in the western United States and transmits pathogens that cause diseases of veterinary and public health importance including Rocky Mountain spotted fever, tularemia, Colorado tick fever and bovine anaplasmosis. Tick saliva is known to modulate both innate and acquired immune responses, enabling ticks to feed for several days without detection. During feeding ticks subvert host defenses such as hemostasis and inflammation, which would otherwise result in coagulation, wound repair and rejection of the tick. Molecular characterization of the proteins and pharmacological molecules secreted in tick saliva offers an opportunity to develop tick vaccines as an alternative to the use of acaricides, as well as new anti-inflammatory drugs. We performed proteomics informed by transcriptomics to identify D. andersoni saliva proteins that are secreted during feeding. The transcript data generated a database of 21,797 consensus sequences, which we used to identify 677 proteins secreted in the saliva of D. andersoni ticks fed for 2 and 5 days, following proteomic investigations of whole saliva using mass spectrometry. Salivary gland transcript levels of unfed ticks were compared with 2 and 5 day fed ticks to identify genes upregulated early during tick feeding. We cross-referenced the proteomic data with the transcriptomic data to identify 157 proteins of interest for immunomodulation and blood feeding. Proteins of unknown function as well as known immunomodulators were identified.
- Interference competition in entomopathogenic nematodes: male Steinernema kill members of their own and other species. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Aug 7.
There is evidence of competition within and between helminth species, but the mechanisms involved are not well described. In interference competition, organisms prevent each other from using the contested resource through direct negative interactions, either chemical or physical. Steinernema spp. are entomopathogenic nematodes; they enter a living insect host which they kill and consume with the aid of symbiotic bacteria. Several studies have demonstrated intra- and interspecific competition in Steinernema, mediated by a scramble for resources and by incompatibility of the bacterial symbiont. Here we describe a mechanism by which male Steinernema may compete directly for resources, both food (host) and females, by physically injuring or killing members of another species as well as males of their own species. A series of experiments was conducted in hanging drops of insect haemolymph. Males of each of four species (Steinernemalongicaudum, Steinernemacarpocapsae, Steinernemakraussei and Steinernemafeltiae), representing three of the five phylogenetic clades of the genus, killed each other. Within 48h, up to 86% of pairs included at least one dead male, compared with negligible mortality in single male controls. There was evidence of intraspecific difference: one strain of S. feltiae (4CFMO) killed while another (UK76) did not. Males also killed both females and males of other Steinernema spp. There was evidence of a hierarchy of killing, with highest mortality due to S. longicaudum followed by S. carpocapsae, S. kraussei and S. feltiae. Wax moth larvae were co-infected with members of two Steinernema spp. to confirm that killing also takes place in the natural environment of an insect cadaver. When insects were co-infected with one infective juvenile of each species, S. longicaudum males killed both S. feltiae UK76 and Steinernema hermaphroditum. Wax moths co-infected with larger, equal numbers of S. longicaudum and S. feltiae UK76 produced mainly S. longicaudum progeny, as expected based on hanging drop experiments.
- Editorial for the ICOPA XIII Special Issue. [Editorial]
- Int J Parasitol 2014 Aug; 44(9):579.
- Regulation of gene expression in the protozoan parasite Entamoeba invadens: identification of core promoter elements and promoters with stage-specific expression patterns. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Jul 27.
Developmental switching between life-cycle stages is a common feature among many pathogenic organisms. Entamoeba histolytica is an important human pathogen and is a leading parasitic cause of death globally. During its life cycle, Entamoeba converts between cysts (essential for disease transmission) and trophozoites (responsible for tissue invasion). Despite being central to its biology, the triggers that are involved in the developmental pathways of this parasite are not well understood. In order to define the transcriptional network associated with stage conversion we used Entamoeba invadens which serves as a model system for Entamoeba developmental biology, and performed RNA sequencing at different developmental time points. In this study RNA-Seq data was utilised to define basal transcriptional control elements as well as to identify promoters which regulate stage-specific gene expression patterns. We discovered that the 5' and 3' untranslated regions of E. invadens genes are short, a median of 20 nucleotides (nt) and 26 nt respectively. Bioinformatics analysis of DNA sequences proximate to the start and stop codons identified two conserved motifs: (i) E. invadens Core Promoter Motif - GAAC-Like (EiCPM-GL) (GAACTACAAA), and (ii) E. invadens 3'-U-Rich Motif (Ei3'-URM) (TTTGTT) in the 5' and 3' flanking regions, respectively. Electrophoretic mobility shift assays demonstrated that both motifs specifically bind nuclear protein(s) from E. invadens trophozoites. Additionally, we identified select genes with stage-specific expression patterns and analysed the ability of each gene promoter to drive a luciferase reporter gene during the developmental cycle. This approach confirmed three trophozoite-specific, four encystation-specific and two excystation-specific promoters. This work lays the framework for use of stage-specific promoters to express proteins of interest in a particular life-cycle stage, adding to the molecular toolbox for genetic manipulation of E. invadens and allowing further dissection of factors controlling Entamoeba developmental biology.
- Variation among genotypes in responses to increasing temperature in a marine parasite: evolutionary potential in the face of global warming? [JOURNAL ARTICLE]
- Int J Parasitol 2014 Jul 24.
Climates are changing worldwide, and populations are under selection to adapt to these changes. Changing temperature, in particular, can directly impact ectotherms and their parasites, with potential consequences for whole ecosystems. The potential of parasite populations to adapt to climate change largely depends on the amount of genetic variation they possess in their responses to environmental fluctuations. This study is, to our knowledge, the first to look at differences among parasite genotypes in response to temperature, with the goal of quantifying the extent of variation among conspecifics in their responses to increasing temperature. Snails infected with single genotypes of the trematode Maritrema novaezealandensis were sequentially acclimatised to two different temperatures, 'current' (15°C) and 'elevated' (20°C), over long periods. These temperatures are based on current average field conditions in the natural habitat and those predicted to occur during the next few decades. The output and activity of cercariae (free-swimming infective stages emerging from snails) were assessed for each genotype at each temperature. The results indicate that, on average, both cercarial output and activity are higher at the elevated acclimation temperature. More importantly, the output and activity of cercariae are strongly influenced by a genotype-by-temperature interaction, such that different genotypes show different responses to increasing temperature. Both the magnitude and direction (increase or decrease) of responses to temperature varied widely among genotypes. Therefore, there is much potential for natural selection to act on this variation, and predicting how the trematode M. novaezealandensis will respond to the climate changes predicted for the next century will prove challenging.
- Hc-fau, a novel gene regulating diapause in the nematode parasite Haemonchus contortus. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Jul 21.
Diapause induced in the early fourth stage of Haemonchus contortus is a strategy to adapt this nematode to hostile environmental conditions. In this study, we identified a new gene, Hc-fau, a homologue of human fau and Caenorhabditis elegans Ce-rps30. Hc-fau encodes two proteins through alternative RNA splicing, Hc-FAUA and Hc-FAUB, consisting of 130 and 107 amino acids, respectively. Hc-FAU possesses a diverged ubiquitin-like (UBiL) protein domain and a conserved ribosome protein S30 domain. The protein is ubiquitously expressed, except in the gonad. However Hc-fau transcripts decrease significantly in diapausing L4s of H. contortus. In C. elegans, knockdown of Ce-rps30 confers an extended lifespan, increased lipid storage in the intestine and shortened body length. These morphological characteristics are comparable with dauer larvae of C. elegans, in which the gonad is condensed considerably. In contrast, a shortened lifespan is observed in C. elegans over-expressing Hc-faua, and especially Hc-faub, with hatching failure detected. The genes of insulin/IGF-1 signalling (IIS), TGF-β, cGMP, dafachronic acid (DA), apoptosis (AP) and fatty acids (FA) metabolism are all down-regulated in Ce-rps30RNAi (RNA interference) worms, except for akt-1 and daf-16. However, daf-16 up-regulation is inconsistent with its target gene down-regulation and the result from a heat stress assay in these worms. Daf-16 RNAi conducted in Ce-rps30 (tm6034/nt1) mutants failed to rescue the worms. The S30 domain stays in the nucleus, while UBiL accumulates in the cytoplasm. Compared with Hc-FAUA, results of UBiL domain and S30 domain over-expression indicate synergism between UBiL and S30 in regulating lifespan and reproduction. These results suggest the potential functions of Hc-fau in regulating larval diapause in H.contortus.
- Neuropeptidergic control of the hindgut in the black-legged tick Ixodes scapularis. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Jul 21.
The hindgut, as a part of the tick excretory system, plays an important physiological role in maintaining homoeostases and waste elimination. Immunoreactive projections from the synganglion to the hindgut were found using antibodies against four different neuropeptides: FGLamide related allatostatin, myoinhibitory peptide, SIFamide, and orcokinin. The presence of FGLamide related allatostatin, myoinhibitory peptide and SIFamide in both synganglia (source) and hindgut (target organ) extracts was confirmed by MALDI-TOF. Tissue-specific PCR revealed the expression of four putative FGLamide related allatostatin receptors and an SIFamide receptor in the hindgut. An antibody against Ixodes scapularis SIFamide receptor detected immunoreactive spots in epithelial cells as well as the visceral muscles surrounding the rectal sac, while staining with the antibody against myoinhibitory peptide receptor 1 revealed that the immunoreactivity was only associated with the visceral muscles. In hindgut motility assays, SIFamide activated hindgut motility in a dose-dependent manner. None of other three neuropeptides (FGLamide related allatostatin, myoinhibitory peptide and orcokinin) activated hindgut motility when tested alone. Myoinhibitory peptide antagonised the SIFamide-stimulated hindgut mobility when it was tested in combination with SIFamide.