104 research outputs found
Trypanosomatids are common and diverse parasites of Drosophila
No full textDrosophila melanogaster is an important model system of immunity and parasite resistance, yet most studies use parasites that do not naturally infect this organism. We have studied trypanosomatids in natural populations to assess the prevalence and diversity of these gut parasites. We collected several species of Drosophila from Europe and surveyed them for trypanosomatids using conserved primers for two genes. We have used the conserved GAPDH sequence to construct a phylogenetic tree and the highly variable spliced leader RNA to assay genetic diversity. All 5 of the species that we examined were infected, and the average prevalence ranged from 1 to 6%. There are several different groups of trypanosomatids, related to other monoxenous Trypanosomatidae. These may represent new trypanosomatid species and were found in different species of European Drosophila from different geographical locations. The detection of a little studied natural pathogen in D. melanogaster and related species provides new opportunities for research into both the Drosophila immune response and the evolution of hosts and parasites.</p
Viral susceptibility across host species is largely independent of dietary protein to carbohydrate ratios
No full textThis is the final version. Available on open access from Wiley via the DOI in this record Data Repository:
mcmcglmm_data_diet.csv. figshare. Dataset.
https://doi.org/10.6084/m9.figshare.13079465.v1The likelihood of a successful host shift of a parasite to a novel host species can be influenced by environmental factors that can act on both the host and parasite. Changes in nutritional resource availability have been shown to alter pathogen susceptibility and the outcome of infection in a range of systems. Here we examined how dietary protein to carbohydrate altered susceptibility in a large cross infection experiment. We infected 27 species of Drosophilidae with an RNA virus on three food types of differing protein to carbohydrate ratios. We then measured how viral load and mortality across species was affected by changes in diet. We found that changes in the protein:carbohydrate in the diet did not alter the outcomes of infection, with strong positive inter‐species correlations in both viral load and mortality across diets, suggesting no species by diet interaction. Mortality and viral load were strongly positively correlated, and this association was consistent across diets. This suggests changes in diet may give consistent outcomes across host species, and may not be universally important in determining host susceptibility to pathogens.Wellcome TrustRoyal Societ
Supplementary figures S1-S3
No full text<p>Supplementary Figure 1.</p>
<p>Results of permutation tests of population differentiation between the sequences of viruses taken from different categories of host: (a) between arthropods and vertebrates, (b) between arthropods and plants and (c) between plants and vertebrates. Red lines show the degree of differentiation, measured using Hudson’s Fstestimator, and grey histograms show the Fst values from 1000 unique random permutations of host categories over viral sequences. We found significant differentiation between each pair of categories (Fst values: a=0.07, b=0.35, c=0.48) with none of the 1000 permutations resulting in as high an Fst value as the data (P<0.001 for all).</p>
<p>Supplementary Figure 2.</p>
<p>Correlation of the evolutionary distances between rhabdovirueses and the evolutionary distances between their arthropod hosts. Figure shows the results of a permutation test of this relationship (measured by Pearson’s correlation coefficient). The red line shows the true correlation coefficient (0.36), and the grey histogram shows the correlation coefficients returned from 1000 unique random permutations of host genera over viral sequences (see Methods). We found a significant association between viral and host phylogenies with none of the 1000 permutations resulting in as strong a correlation as the data (P<0.001).</p>
<p>Supplementary Figure 3.</p>
<p>Results of the permutation test of population differentiation between the sequences of viruses taken from land and aquatic arthropod and vertebrate hosts. Only arthropod and vertebrate hosts were included in the test, since aquatic hosts only included arthropods and vertebrates. The red line shows the true degree of differentiation, measured using Hudson’s Fstestimator, and the grey histogram shows the Fst values returned from 1000 unique random permutations of host categories over viral sequences. Viruses from terrestrial and aquatic hosts were found to have significant population differentiation (with only 7 of the 1000 permutations resulted in as high an Fst value as the data (Fst =0.07, P=0.007).</p
Dementia Prevalence Estimates in Sub-Saharan Africa: Comparison of two Diagnostic Criteria.
No full textWe have previously reported the prevalence of dementia in older adults living in the rural Hai district of Tanzania according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria. The aim of this study was to compare prevalence rates using the DSM-IV criteria with those obtained using the 10/66 diagnostic criteria, which is specifically designed for use in low- and middle-income countries. In phase I, 1,198 people aged 70 and older were screened for dementia. A stratified sample of 296 was then clinically assessed for dementia according to the DSM-IV criteria. In addition, data were collected according to the protocol of the 10/66 Dementia Research Group, which allowed a separate diagnosis of dementia according to these criteria to be established. The age-standardised prevalence of clinical DSM-IV dementia was 6.4% (95% confidence interval [CI] 4.9-7.9%) and of '10/66 dementia' was 21.6% (95% CI 17.5-25.7%). Education was a significant predictor of '10/66 dementia', but not of DSM-IV dementia. There are large discrepancies in dementia prevalence rates depending on which diagnostic system is used. In rural sub-Saharan Africa, it is not clear whether the association between education and dementia using the 10/66 criteria is a genuine effect or the result of an educational bias within the diagnostic instrument. Despite its possible flaws, the DSM-IV criteria represent an international standard for dementia diagnosis. The 10/66 diagnostic criteria may be more appropriate when identification of early and mild cognitive impairment is required
Heterogeneities in infection outcomes across species: sex and tissue differences in virus susceptibility
No full textSpecies vary in their susceptibility to pathogens, and this can alter the ability of a pathogen to infect a novel host. However, many factors can generate heterogeneity in infection outcomes, obscuring our ability to understand pathogen emergence. Such heterogeneities can alter the consistency of responses across individuals and host species. For example, sexual dimorphism in susceptibility means males are often intrinsically more susceptible than females (although this can vary by host and pathogen). Further, we know little about whether the tissues infected by a pathogen in one host are the same in another species, and how this relates to the harm a pathogen does to its host. Here, we first take a comparative approach to examine sex differences in susceptibility across 31 species of Drosophilidae infected with Drosophila C Virus (DCV). We found a strong positive inter-specific correlation in viral load between males and females, with a close to 1:1 relationship, suggesting that susceptibility to DCV across species is not sex specific. Next, we made comparisons of the tissue tropism of DCV across seven species of fly. We found differences in viral load between the tissues of the seven host species, but no evidence of tissues showing different patterns of susceptibility in different host species. We conclude that, in this system, patterns of viral infectivity across host species are robust between males and females, and susceptibility in a given host is general across tissue types
Emerging pathogen evolution: Using evolutionary theory to understand the fate of novel infectious pathogens.
No full textEvolutionary biology is key to potentially predicting virulence and transmission after a pathogen jumps into a new host species. This knowledge would be valuable for designing public health strategies
Viral susceptibility across host species is largely independent of dietary protein to carbohydrate ratios
No full textThe likelihood of a successful host shift of a parasite to a novel host species can be influenced by environmental factors that can act on both the host and parasite. Changes in nutritional resource availability have been shown to alter pathogen susceptibility and the outcome of infection in a range of systems. Here we examined how dietary protein to carbohydrate altered susceptibility in a large cross infection experiment. We infected 27 species of Drosophilidae with an RNA virus on three food types of differing protein to carbohydrate ratios. We then measured how viral load and mortality across species was affected by changes in diet. We found that changes in the protein:carbohydrate in the diet did not alter the outcomes of infection, with strong positive inter‐species correlations in both viral load and mortality across diets, suggesting no species by diet interaction. Mortality and viral load were strongly positively correlated, and this association was consistent across diets. This suggests changes in diet may give consistent outcomes across host species, and may not be universally important in determining host susceptibility to pathogens
Feminism and the Critique of Violence: negotiating feminist political agency
No full textThe acute sensitivity of feminism to violence, in its many different forms and contexts, makes it a particularly interesting case for the examination of the relationship between politics and violence in theory and practice. Our purpose in this paper is not to adjudicate the normative question of whether feminism implies a commitment to pacifism or to the use of non-violence. Rather, we are interested in examining how the relation between feminist politics and violence is construed as feminists struggle to develop a politics in which opposition to patriarchal violence is central. We begin with the feminist critique of violence, and move to examine how particular articulations of that critique shape and are shaped by practices of feminist political agency in specific contestation over the goals and strategies of feminism. We use the well-known case of feminist debates over the Greenham Common Peace Camp in the UK in the 1980s to demonstrate how negotiating women's political agency in relation to opposition to male violence poses problems, both for feminists who embrace non-violence and prioritize the opposition to war, and for feminists who are suspicious of non-violence and of the association of feminism with peace activism. In both cases, the debates over Greenham demonstrate the fundamentally political character of the ways in which the relation and distinction between violence and politics are conceptually and practically negotiated
El Conflicto de Atlántico Sur : Doctrinas de mando terrestres en presencia
No full textEsta ponencia contempla la presentación del Combate del Monte Longdon (Defensa de Puerto Argentino), como caso testigo de la expresión del título: “Doctrinas de mando terrestres en presencia”, repasando la situación general en el que se circunscribió. Comenzaré tipificando las doctrinas de mando terrestres para luego describir los niveles de la conducción afectados en el conflicto y cómo esos niveles influyen desde arriba hacia abajo y de esta forma se alcanzan a ver claramente las doctrinas de mando en presencia en cada uno de los niveles involucrados en la defensa de Pto. Argentino. Consideraré, brevemente, desde los niveles de la conducción estratégica (nacional, militar y operacional) hasta llegar al del enfrentamiento en el terreno (táctica): la Brigada de Infantería Mecanizada X (+), dentro de ella, el Regimiento de Infantería Mecanizado 7 (RI Mec 7 – Sector defensivo “Plata”) y en su despliegue, a la Compañía B (Subsector defensivo “Plata 2”).Facultad de Humanidades y Ciencias de la Educació
Changes in temperature alter the potential outcomes of virus host shifts
No full textThis is the author accepted manuscript. The final version is available from Public Library of Science via the DOI in this record.Full project dataset: https://figshare.com/account/home#/projects/30692Host shifts – where a pathogen jumps between different host species – are an important source of emerging infectious disease. With on-going climate change there is an increasing need to understand the effect changes in temperature may have on emerging infectious disease. We investigated whether species’ susceptibilities change with temperature and ask if susceptibility is greatest at different temperatures in different species. We infected 45 species of Drosophilidae with an RNA virus and measured how viral load changes with temperature. We found the host phylogeny explained a large proportion of the variation in viral load at each temperature, with strong phylogenetic correlations between viral loads
across temperature. The variance in viral load increased with temperature, while the mean viral load did not. This suggests that as temperature increases the most susceptible species become more susceptible, and the least susceptible less so. We found no significant relationship between a species’ susceptibility across temperatures, and proxies for thermal optima (critical thermal maximum and minimum or basal metabolic rate). These results suggest that whilst the rank order of species susceptibilities may remain the same with changes in temperature, some species may become more susceptible to a novel pathogen, and others less so
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