The application of Global Burden of Animal Diseases methodology to aquatic animal production.

The Global Burden of Animal Diseases (GBADs) programme's key objective â€" to provide a systematic approach to determine the burden of animal disease â€" is as relevant to aquatic as to terrestrial animal production systems. However, to date GBADs methods have mainly been applied to terrestrial animal production systems. The challenges in applying GBADs methods, notably the Animal Health Loss Envelope (AHLE), vary considerably by production system. The authors demonstrate how the AHLE can be calculated for rainbow trout production in England and Wales and acknowledge that its application to other systems (e.g. hatchery production, polyculture and no-feed mollusc production) is more complex. For example, in small scale tropical fish production the impact of suboptimal nutrition on production would need to be addressed. Recirculating aquaculture systems have inherent high levels of biosecurity and disease control, and thus low levels of disease. Removing the capital and running costs associated with biosecurity fundamentally changes the system and invalidates the AHLE calculation. Lack of data from many systems, notably small-scale tropical finfish farming, means that expert opinion will be needed to support the application of GBADs methods. While calculation of the AHLE is the focus of this article, it should be noted that attribution to causes and value chain modelling are needed to generate data on the wider societal impact of aquatic animal diseases (and possible interventions), which governments require to support decision-making about resource allocation.

Les principaux objectifs du programme " Impact mondial des maladies animales " (GBADs) visent à fournir une méthode systématique pour déterminer l'impact des maladies animales et sont pertinents aussi bien pour les systèmes de production d'animaux terrestres que pour les systèmes aquacoles. Néanmoins, à ce jour, les méthodes du GBADs ont surtout été appliquées aux systèmes de production d'animaux terrestres. Les difficultés d'application des méthodes du GBADs, en particulier le calcul de l'enveloppe des pertes sanitaires animales varient considérablement d'un système de production à l'autre. Les auteurs décrivent la méthode appliquée pour calculer l'enveloppe des pertes sanitaires animales dans les élevages de truites arc-en-ciel en Angleterre et au pays de Galles, méthode dont ils reconnaissent que l'application à d'autres systèmes (par exemple la production en écloserie, la polyculture et la production de mollusques sans intrants de fourrage) est plus complexe. Par exemple, dans la production de poissons tropicaux à petite échelle, l'impact d'une nutrition sous-optimale sur la production devrait être pris en compte. Les systèmes de recirculation fermée en aquaculture garantissent intrinsèquement des niveaux élevés de biosécurité et de contrôle sanitaire qui se traduisent par un niveau faible de maladies. La suppression des coûts d'investissement et de fonctionnement associés à la biosécurité modifie fondamentalement le système et invalide le calcul de l'enveloppe des pertes sanitaires animales. Compte tenu de l'absence de données disponibles concernant un grand nombre de systèmes, notamment les petits élevages de poissons tropicaux, il faudra recourir aux avis d'experts pour étayer l'application des méthodes du GBADs. Si l'article aborde essentiellement le calcul de l'enveloppe des pertes sanitaires animales, les auteurs signalent l'importance de rechercher les causes et de modéliser les chaînes de valeur afin de générer des données représentatives de l'impact sociétal au sens large des maladies affectant les animaux aquatiques (ainsi que des interventions envisageables), outils indispensables pour étayer les décisions gouvernementales concernant les ressources à allouer.

El objetivo principal del programa sobre el Impacto Global de las Enfermedades Animales (GBADs), a saber, proporcionar un enfoque sistemático para determinar el impacto de dichas enfermedades, es tan pertinente para los sistemas de producción de animales acuáticos como terrestres. Sin embargo, hasta la fecha, los métodos del GBADs se han aplicado principalmente a los sistemas de producción de animales terrestres. Las dificultades que plantea la aplicación de los métodos del GBADs, en particular la cartera de pérdidas en sanidad animal, varían considerablemente según el sistema de producción. Los autores demuestran cómo puede calcularse la cartera de pérdidas en sanidad animal para la producción de trucha arco iris en Inglaterra y Gales y reconocen que su aplicación en otros sistemas (por ejemplo, la producción en viveros, el policultivo y la producción de moluscos sin insumos alimentarios) es más compleja. Por ejemplo, en la producción de peces tropicales a pequeña escala habría que abordar el impacto de una nutrición subóptima en la producción. Los sistemas de recirculación en acuicultura conllevan altos niveles de bioseguridad y control de enfermedades y, por lo tanto, bajos niveles de enfermedad. Si se eliminan los costos de capital y de explotación asociados a la bioseguridad, el sistema cambia radicalmente e invalida el cálculo de la cartera de pérdidas en sanidad animal. La falta de datos de muchos sistemas, especialmente de la cría de peces tropicales a pequeña escala, implica que se necesitará la opinión de expertos para apoyar la aplicación de los métodos del GBADs. Aunque el presente artículo se centra en el cálculo de la cartera de pérdidas en sanidad animal, cabe señalar que la determinación de las causas y la modelización de la cadena de valor son necesarias para generar datos sobre el impacto social más amplio de las enfermedades de los animales acuáticos (y las posibles intervenciones), que los gobiernos necesitan para respaldar la toma de decisiones sobre la asignación de recursos.

Farm level bio-economic modelling of aquatic animal disease and health interventions.

A farm level bio-economic model, for aquatic animal production, of the relationships between inputs (e.g. purchased animals), outputs (e.g. harvested animals) and gross margin (GM) was developed to assess ex-ante the economics of disease and animal health interventions. Feed costs were calculated from estimates of food conversion ratio (FCR), animals harvested and mortality. The model was applied to a typical grow-out rainbow trout (Oncorhynchus mykiss) farm on Lake Titicaca, Peru and a typical shrimp (Paenus vannamei) farm in the Mekong Delta, Vietnam. The model was used in two analyses. Firstly, an approach to assess the burden of disease developed by the Global Burden of Animal Diseases (GBADs) project was adopted. Output under conditions of 'ideal health' was estimated by reducing mortality to zero and removing health costs. GM in both systems increased by approximately 25% when production was kept constant (and stocking rates reduced) and more than doubled if production was allowed to rise (and initial stocking increased). The increase in GM under conditions of ideal compared with current production provided an estimate of the maximum possible benefit from improved health management. Secondly, break-even analysis was used to assess the economics of vaccination against infectious pancreatic necrosis (IPN) vaccine (rainbow trout - RBT) and probiotics (shrimp). If initial stocking was kept constant, and production allowed to rise, break-even points for the intervention (when GM was the same with and without the intervention) were achieved when mortality was reduced by 16% in RBT fry and juvenile and 28% in shrimp. If production was kept constant and benefit realised by reduced initial stocking, the break-even point was achieved for i) vaccination of RBT when mortality in fry and juveniles was reduced by 39%, and ii) probiotics in shrimp production when there was a 15% reduction in mortality (nursery and grow-out), 10% increase in shrimp weight at harvest and 10% improvement in FCR. The results demonstrate how relatively simple models, parameterised with basic farm production data, can assess the burden of disease and quantify ex-ante the potential benefit of interventions. In the absence of trial data, these analyses support decision-making by farmers. The models can be adapted for many aquaculture systems. Farm level results can be extrapolated to estimate disease burden, and benefits of interventions, at regional or national level and thus support informed decision-making and allocation of resources to health management.

Longitudinal imaging of the ageing mouse.

Several non-invasive imaging techniques are used to investigate the effect of pathologies and treatments over time in mouse models. Each preclinical in vivo technique provides longitudinal and quantitative measurements of changes in tissues and organs, which are fundamental for the evaluation of alterations in phenotype due to pathologies, interventions and treatments. However, it is still unclear how these imaging modalities can be used to study ageing with mice models. Almost all age related pathologies in mice such as osteoporosis, arthritis, diabetes, cancer, thrombi, dementia, to name a few, can be imaged in vivo by at least one longitudinal imaging modality. These measurements are the basis for quantification of treatment effects in the development phase of a novel treatment prior to its clinical testing. Furthermore, the non-invasive nature of such investigations allows the assessment of different tissue and organ phenotypes in the same animal and over time, providing the opportunity to study the dysfunction of multiple tissues associated with the ageing process. This review paper aims to provide an overview of the applications of the most commonly used in vivo imaging modalities used in mouse studies: micro-computed-tomography, preclinical magnetic-resonance-imaging, preclinical positron-emission-tomography, preclinical single photon emission computed tomography, ultrasound, intravital microscopy, and whole body optical imaging.

A novel method for classifying cortical state to identify the accompanying changes in cerebral hemodynamics.

BACKGROUND: Many brain imaging techniques interpret the haemodynamic response as an indirect indicator of underlying neural activity. However, a challenge when interpreting this blood based signal is how changes in brain state may affect both baseline and stimulus evoked haemodynamics. NEW METHOD: We developed an Automatic Brain State Classifier (ABSC), validated on data from anaesthetised rodents. It uses vectorised information obtained from the windowed spectral frequency power of the Local Field Potential. Current state is then classified by comparing this vectorised information against that calculated from state specific training datasets. RESULTS: The ABSC identified two user defined brain states (synchronised and desynchronised), with high accuracy (∼90%). Baseline haemodynamics were found to be significantly different in the two identified states. During state defined periods of elevated baseline haemodynamics we found significant decreases in evoked haemodynamic responses to somatosensory stimuli. COMPARISON TO EXISTING METHODS: State classification - The ABSC (∼90%) demonstrated greater accuracy than clustering (∼66%) or 'power threshold' (∼64%) methods of comparison. Haemodynamic averaging - Our novel approach of selectively averaging stimulus evoked haemodynamic trials by brain state yields higher quality data than creating a single average from all trials. CONCLUSIONS: The ABSC can account for some of the commonly observed trial-to-trial variability in haemodynamic responses which arises from changes in cortical state. This variability might otherwise be incorrectly attributed to alternative interpretations. A greater understanding of the effects of cortical state on haemodynamic changes could be used to inform techniques such as general linear modelling (GLM), commonly used in fMRI.

Kinetic modeling of hyperpolarized (13)C pyruvate metabolism in tumors using a measured arterial input function.

Mathematical models are required to estimate kinetic parameters of [1-(13)C] pyruvate-lactate interconversion from magnetic resonance spectroscopy data. One- or two-way exchange models utilizing a hypothetical approximation to the true arterial input function (AIF), (e.g. an ideal 'box-car' function) have been used previously. We present a method for direct measurement of the AIF in the rat. The hyperpolarized [1-(13)C] pyruvate signal was measured in arterial blood as it was continuously withdrawn through a small chamber. The measured signal was corrected for T1 relaxation of pyruvate, RF pulses and dispersion of blood in the chamber to allow for the estimation of the direct AIF. Using direct AIF, rather than the commonly used box-car AIF, provided realistic estimates of the rate constant of conversion of pyruvate to lactate, kpl, the rate constant of conversion of lactate to pyruvate klp, the clearance rate constant of pyruvate from blood to tissue, Kip, and the relaxation rate of lactate T1la. Since no lactate signal was present in blood, it was possible to use a simple precursor-product relationship, with the tumor tissue pyruvate time-course as the input for the lactate time-course. This provided a robust estimate of kpl, similar to that obtained using a directly measured AIF.

Fine detail of neurovascular coupling revealed by spatiotemporal analysis of the hemodynamic response to single whisker stimulation in rat barrel cortex.

The spatial resolution of hemodynamic-based neuroimaging techniques, including functional magnetic resonance imaging, is limited by the degree to which neurons regulate their blood supply on a fine scale. Here we investigated the spatial detail of neurovascular events with a combination of high spatiotemporal resolution two-dimensional spectroscopic optical imaging, multichannel electrode recordings and cytochrome oxidase histology in the rodent whisker barrel field. After mechanical stimulation of a single whisker, we found two spatially distinct cortical hemodynamic responses: a transient response in the "upstream" branches of surface arteries and a later highly localized increase in blood volume centered on the activated cortical column. Although the spatial representation of this localized response exceeded that of a single "barrel," the spread of hemodynamic activity accurately reflected the neural response in neighboring columns rather than being due to a passive "overspill." These data confirm hemodynamics are capable of providing accurate "single-condition" maps of neural activity.

Cocaine administration produces a protracted decoupling of neural and haemodynamic responses to intense sensory stimuli.

Evidence suggests that for relatively weak sensory stimuli, cocaine elevates background haemodynamic parameters but still allows enhanced neural responses to be reflected in enhanced haemodynamic responses. The current study investigated the possibility that for more intense stimuli, the raised background may produce a protracted attenuation of the haemodynamic response. Three experiments were performed to measure effects of i.v. cocaine administration (0.5 mg/kg) or saline on responses in rat barrel cortex to electrical stimulation of the whisker pad. The first experiment used optical imaging spectroscopy (OIS) and laser Doppler flowmetry (LDF) to measure haemodynamic changes. Cocaine caused an increase in baseline blood flow (peak approximately 90%), which lasted for the duration of the test period (25 min). Haemodynamic responses to whisker stimulation were substantially reduced throughout. The second experiment used a 16-channel multi-electrode to measure evoked potentials at 100 mum intervals through the barrel cortex. Summed neural responses (collapsed across the spatial dimension) after cocaine administration were similar to those after saline. The third experiment extended experiment 1 by examining the effects of cocaine on whisker sensory responses using functional magnetic resonance imaging (and concurrent OIS or LDF). Cocaine caused a similar increase in baseline and reduction in the evoked response to that seen in experiment 1. Together, the results of these three experiments show that cocaine produces a protracted decoupling of neural activity and haemodynamic responses to intense sensory stimulation, which suggests that imaging techniques based on changes in haemodynamic parameters may be unsuitable for studying the effects of cocaine on sensory processing in humans.