Regulatory motifs are present in the ITS1 of some flatworm species

Rescue of Infectious Salmon Anemia Virus (ISAV) from Cloned cDNA

The piscine orthomyxovirus called infectious salmon anemia virus (ISAV) is one of the most important emerging pathogens affecting the salmon industry worldwide. The first reverse genetics system for ISAV, which allows the generation of recombinant ISA virus (rISAV), is an important tool for the characterization and study of this virus. The plasmid-based reverse genetics system for ISAV includes the use of a novel fish promoter, the Atlantic salmon internal transcribed spacer region 1 (ITS-1). The salmon, viral, and mammalian genetic elements included in the pSS-URG vectors allow the expression of the eight viral RNA segments. In addition to four cytomegalovirus (CMV)-based vectors that express the four proteins of the ISAV ribonucleoprotein complex, the eight pSS-URG vectors allowed the generation of infectious rISAV in salmon cells.

Parasite detection in the ornamental fish trade using environmental DNA

Effective border control relies on stringent biosecurity protocols to detect and prevent introductions of exotic pests and diseases. Detection of pathogens and parasites in the live ornamental fish trade using environmental DNA (eDNA) techniques has the potential to improve current biosecurity practices. We examined water samples from 11 target consignments (cyprinids susceptible to Dactylogyrus spp. infections) and seven non-target fish consignments (non-cyprinids, not susceptible to Dactylogyrus spp. infections) imported from Southeast Asia to Australia for the presence of eDNA from five Dactylogyrus species (Monogenea: Dactylogyridae). A four-step predictive framework was used to predict putative positive and putative negative detections from quantitative PCR assays. Both target and non-target consignments were positive for Dactylogyrus spp. eDNA as confirmed by Sanger sequencing. Positive detections for Dactylogyrus spp. eDNA in non-target fish consignments demonstrates the possibility of source water contamination, limiting the applicability of eDNA screening methods at border control. This study suggests that screening for parasite eDNA within ornamental fish consignments should be tested during pre-export quarantine periods to avoid false positive detections at border control. Lastly, the proposed predictive framework has a broad utility for minimizing false positive and false negative eDNA detections of aquatic organisms.

Rescue of Infectious Salmon Anemia Virus (ISAV) from Cloned cDNA

The piscine Orthomyxovirus called Infectious Salmon Anemia Virus (ISAV) is one of the most important emerging pathogens affecting the salmon industry worldwide. The first reverse genetics system for ISAV, which allows the generation of recombinant ISA virus (rISAV), is an important tool for the characterization and study of this fish virus. The plasmid-based reverse genetics system for ISAV includes the use of a novel fish promoter, the Atlantic salmon internal transcribed spacer region 1 (ITS-1). The salmon, viral and mammalian genetic elements included in pSS-URG vectors allow the expression of the eight viral RNA segments. In addition to four cytomegalovirus (CMV)-based vectors that express the four proteins of the ISAV ribonucleoprotein complex, the eight pSS-URG vectors allowed the generation of infectious rISAV in salmon cells.

Development of a reverse genetic system for infectious salmon anemia virus: rescue of recombinant fluorescent virus by using salmon internal transcribed spacer region 1 as a novel promoter

Infectious salmon anemia (ISA) is a serious disease of marine-farmed Atlantic salmon (Salmo salar) caused by ISA virus (ISAV), belonging to the genus Isavirus, family Orthomyxoviridae. There is an urgent need to understand the virulence factors and pathogenic mechanisms of ISAV and to develop new vaccine approaches. Using a recombinant molecular biology approach, we report the development of a plasmid-based reverse genetic system for ISAV, which includes the use of a novel fish promoter, the Atlantic salmon internal transcribed spacer region 1 (ITS-1). Salmon cells cotransfected with pSS-URG-based vectors expressing the eight viral RNA segments and four cytomegalovirus (CMV)-based vectors that express the four proteins of the ISAV ribonucleoprotein complex allowed the generation of infectious recombinant ISAV (rISAV). We generated three recombinant viruses, wild-type rISAV(901_09) and rISAVr(S6-NotI-HPR) containing a NotI restriction site and rISAV(S6/EGFP-HPR) harboring the open reading frame of enhanced green fluorescent protein (EGFP), both within the highly polymorphic region (HPR) of segment 6. All rescued viruses showed replication activity and cytopathic effect in Atlantic salmon kidney-infected cells. The fluorescent recombinant viruses also showed a characteristic cytopathic effect in salmon cells, and the viruses replicated to a titer of 6.5105 PFU/ml,similar to that of the wild-type virus. This novel reverse genetics system offers a powerful tool to study the molecular biology of ISAV and to develop a new generation of ISAV vaccines to prevent and mitigate ISAV infection, which has had a profound effect on the salmon industry.

Populations, hybrids and the systematic concepts of species and subspecies in Chagas disease triatomine vectors inferred from nuclear ribosomal and mitochondrial DNA

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.

Coevolution of Retrovarium n. gen. (Digenea: Cryptogonimidae) in Lutjanidae and Haemulidae (Perciformes) in the Indo-West Pacific

We describe 11 new species of cryptogonimids belonging to Retrovarium n. gen., from eight species of Lutjanidae and one species of Haemulidae, from the Great Barrier Reef, French Polynesia and the Maldives. We also transfer Neoparacryptogonimus saccatus (Manter, 1963) and Neoparacryptogonimus sphericus Nahhas, Sey & Nishimoto, 1998 to Retrovarium. The morphologically based taxonomic approach was augmented with DNA sequence data from three nuclear ribosomal DNA regions (28S, ITS1 and ITS2) to explore the species integrity, biogeographic distribution and evolution of the species recognised here. Sequencing included multiple replicates and revealed 11 distinct genotypes which corroborated our morphologically based hypotheses of putative species present in the system. There was no intraspecific variation and all three rDNA regions differed between every combination of species. Two species exhibited wide geographic ranges, having identical rDNA sequences between the Great Barrier Reef and the Maldives, localities separated by over 9600 km. One host species, Symphorus nematophorus, proved to be exceptionally rich, harbouring six species. Minimum evolution analyses were conducted on each of the rDNA datasets independently; minimum evolution, maximum likelihood and Bayesian inference analyses were conducted on a combined (28S, ITS1 and ITS2) dataset for sequence comparison purposes and to explore the evolutionary history of these parasites. To examine the coevolutionary history of this complex, assessment of phylogenetic relationships between the 23 species of Lutjanidae and two species of Haemulidae collected during this survey was performed with data from 16S and cytochrome b mtDNA using Bayesian inference analysis. Despite the high host specificity observed in most of the species, mapping of the parasites on the host phylogeny revealed an absence of strict coevolution or co-descent within this complex. Overall, Retrovarium appears to have had an exceptionally patchy radiation, failing to infect many taxa, infecting species with no readily discernible pattern, and radiating dramatically within one species.