Veterinary Science - Research Publications
Now showing items 1-12 of 176
Costing the morbidity and mortality consequences of zoonoses using health-adjusted life years
(Blackwell Publishing Ltd, 2015)
Governments are routinely involved in the biosecurity of agricultural and food imports and exports. This involves controlling the complex ongoing threat of the broad range of zoonoses: endemic, exotic and newly emerging. Policy-related decision-making in these areas requires accurate information and predictions concerning the effects and potential impacts of zoonotic diseases. The aim of this article was to provide information concerning the development and use of utility-based tools, specifically disability-adjusted life years (DALYs), for measuring the burden on human disease (morbidity and mortality) as a consequence of zoonotic infections. Issues and challenges to their use are also considered. Non-monetary utility approaches that are reviewed in this paper form one of a number of tools that can be used to estimate the monetary and non-monetary 'cost' of morbidityand mortality-related consequences. Other tools derive from cost-of-illness, willingness-to-pay and multicriteria approaches. Utility-based approaches are specifically designed to capture the pain, suffering and loss of functioning associated with diseases, zoonotic and otherwise. These effects are typically complicated to define, measure and subsequently 'cost'. Utility-based measures will not be able to capture all of the effects, especially those that extend beyond the health sector. These will more normally be captured in financial terms. Along with other uncommon diseases, the quality of the relevant epidemiological data may not be adequate to support the estimation of losses in utility as a result of zoonoses. Other issues in their use have been identified. New empirical studies have shown some success in addressing these issues. Other issues await further study. It is concluded that, bearing in mind all caveats, utility-based methods are important tools in assessing the magnitude of the impacts of zoonoses in human disease. They make an important contribution to decision-making and priority setting across all sectors. In doing so, they highlight the relative importance of the burden of zoonotic disease globally.
Seroprevalence and Risk Factors for Taenia solium Cysticercosis in Rural Pigs of Northern Peru
(PUBLIC LIBRARY SCIENCE, 2012)
Taenia solium is a cestode parasite that causes cysticercosis in both humans and pigs. A serological survey was undertaken to assess the seroprevalence and risk factors associated with porcine cysticercosis in the rural district of Morropon, Peru. Pigs aged between 2 and 60 months were assessed by the Enzyme-linked Immunoelectrotransfer blot (EITB) assay to determine their serological status against porcine cysticercosis in a cross-sectional study. A total of 1,153 pigs were sampled. Porcine seroprevalence was 45.19% (42.31-48.06). The information about the animals and households was analyzed and risk factors associated with seroprevalence were determined by a multivariate logistic regression analysis. In the porcine population, the risk of being seropositive increased by 7% with every month of age (OR 1.07, 95% CI 1.05-1.09), and by 148% for pigs living in East Morropon (OR 2.48, 95% CI 1.82-3.37). Whereas, the presence of latrines in a household decreased the risk of being seropositive by 49% (OR 0.51; 95% CI 0.39-0.67). Sex and rearing system did not represent either risk or protective factors associated with the seroprevalence of porcine cysticercosis. The findings of this study could be used for further development of control programs that might focus on similar population groups within rural communities of developing countries where cysticercosis is endemic.
The complete genome sequence of the avian pathogen Mycoplasma gallisepticum strain R-low
(SOC GENERAL MICROBIOLOGY, 2003-09-01)
The complete genome of Mycoplasma gallisepticum strain R(low) has been sequenced. The genome is composed of 996,422 bp with an overall G+C content of 31 mol%. It contains 742 putative coding DNA sequences (CDSs), representing a 91 % coding density. Function has been assigned to 469 of the CDSs, while 150 encode conserved hypothetical proteins and 123 remain as unique hypothetical proteins. The genome contains two copies of the rRNA genes and 33 tRNA genes. The origin of replication has been localized based on sequence analysis in the region of the dnaA gene. The vlhA family (previously termed pMGA) contains 43 genes distributed among five loci containing 8, 2, 9, 12 and 12 genes. This family of genes constitutes 10.4% (103 kb) of the total genome. Two CDSs were identified immediately downstream of gapA and crmA encoding proteins that share homology to cytadhesins GapA and CrmA. Based on motif analysis it is predicted that 80 genes encode lipoproteins and 149 proteins contain multiple transmembrane domains. The authors have identified 75 proteins putatively involved in transport of biomolecules, 12 transposases, and a number of potential virulence factors. The completion of this sequence has spawned multiple projects directed at defining the biological basis of M. gallisepticum.
Endothelial Dysfunction in an Ovine Model of Collagen-Induced Arthritis
Background: Rheumatoid arthritis (RA) induces systemic inflammation, producing a range of co-morbidities including cardiovascular disease. An early vascular change is endothelial dysfunction, characterized by reduced endothelium-dependent vasodilation. The aim of this study was to assess endothelial function in isolated coronary and digital arteries using an ovine model of collagen-induced RA. Methods: Sheep were culled following induction of arthritis, and their endothelial function was compared to that of normal sheep. Paired arterial segments were mounted in a wire myograph and dilated with endothelium-dependent vasodilators [bradykinin, serotonin, carbachol and adenosine diphosphate (ADP); linked to either Gi or Gq signalling pathways] and endothelium-independent dilators (adenosine and sodium nitroprusside) to construct cumulative concentration-response curves. Results: Coronary arteries from arthritic sheep exhibited a significantly greater EC50 value for bradykinin-induced relaxation compared to non-arthritic controls (2.9 × 10-8M for arthritic sheep vs. 8.6 × 10-9M for controls). Digital arteries from arthritic sheep also exhibited a significantly greater EC50 for relaxation to ADP and a significant decrease in the carbachol maximal response. Responses to sodium nitroprusside were unchanged in both coronary and digital arteries. Conclusion: Sheep with RA demonstrated attenuated arterial relaxation to endothelium-dependent vasodilators. This may provide a useful model of endothelial dysfunction in chronic inflammatory conditions. The dysfunction did not appear to be associated with one specific G-protein signalling pathway. © 2014 S. Karger AG, Basel.
Molecular Characterization of Coccidia Associated with an Epizootic in Green Sea Turtles (Chelonia mydas) in South East Queensland, Australia
(PUBLIC LIBRARY SCIENCE, 2016-02-22)
In the spring of 2014, mass mortalities among wild green sea turtles occurred off the coast of south-east Queensland, Australia. The suspected causative agent was Caryospora cheloniae, an eimeriid coccidian implicated in previous epizootics. Necropsies were undertaken on a subset of 11 dead turtles, with subsequent histopathology and molecular analyses. All turtles returned positive PCR results for coccidial infection in various tissues; these included the brain, gastrointestinal tract, lung, kidney and thyroid. Granulomatous encephalitis was consistently observed, as well as enteritis and, less frequently, thyroiditis and nephritis. Sequencing and phylogenetic analyses indicated the presence of two distinct coccidian genotypes, presumably separate species-one associated with the brain, gastrointestinal tract and lung, and the second with the thyroid and kidney. Maximum likelihood and Bayesian inference analyses placed the first genotype closest to the lankesterellid genus Schellackia, rather than in the Eimeriidae, while the second was paraphyletic to the eimeriids. Presence of coccidial stages in extra-intestinal tissues of the primary host raises questions about the potential presence of intermediate or paratenic hosts within the life cycles, as well as their current placement relative to the genus Caryospora. This study represents the first genetic characterization of this emerging disease agent in green sea turtles, an endangered species, and has relevance for life-cycle elucidation and future development of diagnostics.
NetB, a new toxin that is associated with avian necrotic enteritis caused by Clostridium perfringens
(PUBLIC LIBRARY SCIENCE, 2008-02-01)
For over 30 years a phospholipase C enzyme called alpha-toxin was thought to be the key virulence factor in necrotic enteritis caused by Clostridium perfringens. However, using a gene knockout mutant we have recently shown that alpha-toxin is not essential for pathogenesis. We have now discovered a key virulence determinant. A novel toxin (NetB) was identified in a C. perfringens strain isolated from a chicken suffering from necrotic enteritis (NE). The toxin displayed limited amino acid sequence similarity to several pore forming toxins including beta-toxin from C. perfringens (38% identity) and alpha-toxin from Staphylococcus aureus (31% identity). NetB was only identified in C. perfringens type A strains isolated from chickens suffering NE. Both purified native NetB and recombinant NetB displayed cytotoxic activity against the chicken leghorn male hepatoma cell line LMH; inducing cell rounding and lysis. To determine the role of NetB in NE a netB mutant of a virulent C. perfringens chicken isolate was constructed by homologous recombination, and its virulence assessed in a chicken disease model. The netB mutant was unable to cause disease whereas the wild-type parent strain and the netB mutant complemented with a wild-type netB gene caused significant levels of NE. These data show unequivocally that in this isolate a functional NetB toxin is critical for the ability of C. perfringens to cause NE in chickens. This novel toxin is the first definitive virulence factor to be identified in avian C. perfringens strains capable of causing NE. Furthermore, the netB mutant is the first rationally attenuated strain obtained in an NE-causing isolate of C. perfringens; as such it has considerable vaccine potential.
ISMapper: identifying transposase insertion sites in bacterial genomes from short read sequence data
(BIOMED CENTRAL LTD, 2015-09-03)
BACKGROUND: Insertion sequences (IS) are small transposable elements, commonly found in bacterial genomes. Identifying the location of IS in bacterial genomes can be useful for a variety of purposes including epidemiological tracking and predicting antibiotic resistance. However IS are commonly present in multiple copies in a single genome, which complicates genome assembly and the identification of IS insertion sites. Here we present ISMapper, a mapping-based tool for identification of the site and orientation of IS insertions in bacterial genomes, directly from paired-end short read data. RESULTS: ISMapper was validated using three types of short read data: (i) simulated reads from a variety of species, (ii) Illumina reads from 5 isolates for which finished genome sequences were available for comparison, and (iii) Illumina reads from 7 Acinetobacter baumannii isolates for which predicted IS locations were tested using PCR. A total of 20 genomes, including 13 species and 32 distinct IS, were used for validation. ISMapper correctly identified 97 % of known IS insertions in the analysis of simulated reads, and 98 % in real Illumina reads. Subsampling of real Illumina reads to lower depths indicated ISMapper was able to correctly detect insertions for average genome-wide read depths >20x, although read depths >50x were required to obtain confident calls that were highly-supported by evidence from reads. All ISAba1 insertions identified by ISMapper in the A. baumannii genomes were confirmed by PCR. In each A. baumannii genome, ISMapper successfully identified an IS insertion upstream of the ampC beta-lactamase that could explain phenotypic resistance to third-generation cephalosporins. The utility of ISMapper was further demonstrated by profiling genome-wide IS6110 insertions in 138 publicly available Mycobacterium tuberculosis genomes, revealing lineage-specific insertions and multiple insertion hotspots. CONCLUSIONS: ISMapper provides a rapid and robust method for identifying IS insertion sites directly from short read data, with a high degree of accuracy demonstrated across a wide range of bacteria.
More parasiticmyositis cases in humans in Australia, and the definition of genetic markers for the causative agents as a basis for molecular diagnosis
(ELSEVIER SCIENCE BV, 2016-10-01)
Since 1998, there have been six reported human cases of myositis in Australia, attributable to infection with the nematode Haycocknema perplexum. However, an unequivocal diagnosis of H. perplexum infection and associated disease has been seriously compromised by a lack of molecular markers for this nematode. Here, we report new cases of disseminated myositis in two male patients from the states of Queensland and Tasmania in Australia, respectively; genetically characterize the causative agent from each case; and, also establish a PCR-based sequencing approach as a tool to support the diagnosis of future cases and to underpin epidemiological studies.