Visiting Sick People: Is It Really Detrimental to Our Health?

Intuitively, keeping ones distance from a source of infection would appear to be the best way to limit the occurrence of disease. However, this overlooks the importance of repeated infections in maintaining efficient immune defenses. When acquired immunity has partly waned, re-exposure to the pathogenic agent may lead to mild disease that boosts the immune system. This prevents the total loss of immunity that would lead to classical disease in cases of re-infection. Here, using a mathematical model, we show that avoiding the pathogenic agent is detrimental in some situations, e.g. for pathogens that are highly transmissible, are not excessively lethal and that induce rapidly waning immunity. Reducing exposure to pathogenic agents is among the objectives of most, if not all, public health measures. A better understanding of the factors influencing the severity of a disease is required before applying measures that reduce the circulation of pathogenic agents

Animal health perceived in the light of ecology and evolution

Infectious diseases remain a major cause of animal mortality and morbidity. Global changes, including fragmentation of habitats of many animal species, modify the ecology of host-parasite relationships and the selection pressures on infectious agents, introducing high uncertainty about the impact and evolution of these diseases. In such a context, it is important to integrate ecology and evolutionary science to animal health issues for a better understanding and a better management of infectious diseases. From our work we illustrate the contribution of an eco-evolutionary vision of infectious diseases in animals. The first two examples illustrate the importance of including eco-evolutionary dimension to the understanding and management of infectious animal diseases. The last two sections show that, in turn, the data collected in the field can also provide fundamental knowledge on important issues that are often addressed in the laboratory. Given their complexity, these issues can only be addressed by iterating back and forth between experimental data and mathematical modelingLes maladies infectieuses demeurent une cause majeure de mortalité en santé animale. Les changements globaux, notamment la fragmentation des habitats de nombreuses espèces animales, modifient l’écologie des relations hôtes-parasites et les pressions qui s’exercent sur les agents infectieux, introduisant une importante incertitude sur l’impact et l’évolution de ces maladies. Dans un tel contexte, il est important d’intégrer les sciences de l’Écologie et de l’Évolution aux problèmes de santé animale pour une meilleure compréhension et une meilleure gestion des maladies infectieuses. Nous illustrons à partir de nos travaux les apports d’une vision éco-évolutionniste des maladies infectieuses chez l’animal. Les deux premiers exemples illustrent l’intérêt d’inclure la dimension éco-évolutive pour la compréhension et la gestion des maladies infectieuses animales. Les deux dernières parties montrent qu’en retour, les données recueillies sur le terrain peuvent également apporter une connaissance fondamentale sur des questions importantes qui sont le plus souvent abordées en laboratoire. Compte-tenu de leur complexité, ces questions ne peuvent être traitées que par des allers-retours entre données et modélisation mathématiqu

Analysis of high altitude clouds in the martian atmosphere based on Mars Climate Sounder observations

International Symposium on Sun, Earth, and Life, Jun 2016, Bandung, IndonesiaInternational audienceHigh altitude clouds have been observed in the Martian atmosphere. However, their properties still remain to be characterized. Mars Climate Sounder (MCS) aboard Mars Reconnaissance Orbiter (MRO) is an instrument that measures radiances in the thermal infrared, both in limb and nadir views. It allows us to retrieve vertical profiles of radiance, temperature and aerosols. Using the MCS data and radiative transfer model coupled with an automated inversion routine, we can investigate the chemical composition of the high altitude clouds. We will present the first results on the properties of the clouds. CO2 ice is the best candidate to be the main component of some high altitude clouds due to the most similar spectral variation compared to water ice or dust, in agreement with previous studies. Using cloud composition of contaminated CO2 ice (dust core surrounded by CO2 ice) might improve the fitting result, but further study is needed

Parasite-Parasite Interactions in the Wild: How To Detect Them?

International audienceInter-specific interactions between parasites impact on parasite intra-hostdynamics, host health, and disease management. Identifying and understandinginteraction mechanisms in the wild is crucial for wildlife disease management.It is however complex because several scales are interlaced. Parasite–parasite interactions are likely to occur via mechanisms at the within-host level,but also at upper levels (host population and community). Furthermore, interactionsoccurring at one level of organization spread to upper levels throughcascade effects. Even if cascade effects are important confounding factors, weargue that we can also benefit from them because upper scales often provide away to survey a wider range of parasites at lower cost. New protocols andtheoretical studies (especially across scales) are necessary to take advantage ofthis opportunity

Evolution of microparasites in spatially and genetically structured host populations: The example of RHDV infecting rabbits

International audienc

Engineering the magnetic and magnetocaloric properties of PrVO3 epitaxial oxide thin films by strain effects

Combining multiple degrees of freedom in strongly-correlated materials such as transition-metal oxides would lead to fascinating magnetic and magnetocaloric features. Herein, the strain effects are used to markedly tailor the magnetic and magnetocaloric properties of PrVO3 thin films. The selection of appropriate thickness and substrate enables us to dramatically decrease the coercive magnetic field from 2.4 T previously observed in sintered PVO3 bulk to 0.05 T for compressive thin films making from the PrVO3 compound a nearly soft magnet. This is associated with a marked enhancement of the magnetic moment and the magnetocaloric effect that reach unusual maximum values of roughly 4.86 uB and 56.8 J/kg K in the magnetic field change of 6 T applied in the sample plane at the cryogenic temperature range (3 K), respectively. This work strongly suggests that taking advantage of different degrees of freedom and the exploitation of multiple instabilities in a nanoscale regime is a promising strategy for unveiling unexpected phases accompanied by a large magnetocaloric effect in oxides.Comment: This paper is accepted for publication in Applied Physics Letter

Coexistence of two sympatric cryptic bat species in French Guiana: insights from genetic, acoustic and ecological data

International audienceBackground: The distinction between lineages of neotropical bats from the Pteronotus parnellii species complex has been previously made according to mitochondrial DNA, and especially morphology and acoustics, in order to separate them into two species. In these studies, either sample sizes were too low when genetic and acoustic or morphological data were gathered on the same individuals, or genetic and other data were collected on different individuals. In this study, we intensively sampled bats in 4 caves and combined all approaches in order to analyse genetic, morphologic, and acoustic divergence between these lineages that live in the same caves in French Guiana

Planetary population synthesis

In stellar astrophysics, the technique of population synthesis has been successfully used for several decades. For planets, it is in contrast still a young method which only became important in recent years because of the rapid increase of the number of known extrasolar planets, and the associated growth of statistical observational constraints. With planetary population synthesis, the theory of planet formation and evolution can be put to the test against these constraints. In this review of planetary population synthesis, we first briefly list key observational constraints. Then, the work flow in the method and its two main components are presented, namely global end-to-end models that predict planetary system properties directly from protoplanetary disk properties and probability distributions for these initial conditions. An overview of various population synthesis models in the literature is given. The sub-models for the physical processes considered in global models are described: the evolution of the protoplanetary disk, the planets' accretion of solids and gas, orbital migration, and N-body interactions among concurrently growing protoplanets. Next, typical population synthesis results are illustrated in the form of new syntheses obtained with the latest generation of the Bern model. Planetary formation tracks, the distribution of planets in the mass-distance and radius-distance plane, the planetary mass function, and the distributions of planetary radii, semimajor axes, and luminosities are shown, linked to underlying physical processes, and compared with their observational counterparts. We finish by highlighting the most important predictions made by population synthesis models and discuss the lessons learned from these predictions - both those later observationally confirmed and those rejected.Comment: 47 pages, 12 figures. Invited review accepted for publication in the 'Handbook of Exoplanets', planet formation section, section editor: Ralph Pudritz, Springer reference works, Juan Antonio Belmonte and Hans Deeg, Ed

Using Dynamic Stochastic Modelling to Estimate Population Risk Factors in Infectious Disease: The Example of FIV in 15 Cat Populations

BACKGROUND:In natural cat populations, Feline Immunodeficiency Virus (FIV) is transmitted through bites between individuals. Factors such as the density of cats within the population or the sex-ratio can have potentially strong effects on the frequency of fight between individuals and hence appear as important population risk factors for FIV. METHODOLOGY/PRINCIPAL FINDINGS:To study such population risk factors, we present data on FIV prevalence in 15 cat populations in northeastern France. We investigate five key social factors of cat populations; the density of cats, the sex-ratio, the number of males and the mean age of males and females within the population. We overcome the problem of dependence in the infective status data using sexually-structured dynamic stochastic models. Only the age of males and females had an effect (p = 0.043 and p = 0.02, respectively) on the male-to-female transmission rate. Due to multiple tests, it is even likely that these effects are, in reality, not significant. Finally we show that, in our study area, the data can be explained by a very simple model that does not invoke any risk factor. CONCLUSION:Our conclusion is that, in host-parasite systems in general, fluctuations due to stochasticity in the transmission process are naturally very large and may alone explain a larger part of the variability in observed disease prevalence between populations than previously expected. Finally, we determined confidence intervals for the simple model parameters that can be used to further aid in management of the disease