A Coupled Model of Population, Poaching, and Economic Dynamics to Assess Rhino Conservation Through Legal Trade

Rhinoceros populations in Africa are in peril largely due to the high value of their horns and the poaching that ensues. The strategy of legalizing the international trade of rhino horn is receiving increased support among both the people and government officials in Africa. Many in the international conservation community remain opposed to the idea. The legalization strategy is straightforward in theory: legalizing the trade of rhino horn will introduce a large quantity of horn to the market, the increased supply will lead to lower prices for rhino horn, and lower prices will reduce the overall poaching pressure these animals face. In this work, we propose a model for rhino populations that includes the interrelated dynamics of the price of rhino horn and poaching rates to establish thresholds of parameter values for which legalization can either increase or decrease rhino populations

Feasible and ethical allocation of intervention resources for infectious diseases using linear programming

In this work, we demonstrate that the consideration of a fixed epidemic and the use of linear programming can be an effective tool for designing rollout strategies for infectious disease interventions. Specifically, we argue that the approach can be more flexible, more amenable to detailed allocation plans and more in line with the way that public policy decisions are made than standard optimal control allocations. We also show how feasibility and ethical constraints can be incorporated into resource allocations. As an application, we consider the initial rollout of Treatment as Prevention (TasP) resources for HIV (human immunodeficiency virus) in South Africa that began within the last decade. Going back to TasP’s initial rollout allows us to demonstrate the strengths of this approach.En este trabajo, demostramos que la consideración de una epidemia fija y el uso de la programación lineal puede ser una herramienta efectiva para diseñar estrategias de lanzamiento para intervenciones de enfermedades infecciosas. Específicamente, argumentamos que el enfoque puede ser más flexible, más susceptible a planes de asignación detallados y más en línea con la forma en que se toman las decisiones de política pública que las asignaciones de control óptimo estándar. También, mostramos cómo la viabilidad y las restricciones éticas pueden incorporarse en las asignaciones de recursos. Como aplicación, consideramos la implementación inicial de los recursos de Tratamiento como Prevención (TasP) para el VIH (virus de inmunodeficiencia humana) en Sudáfrica que comenzó en la última década. Volver al lanzamiento inicial de TasP nos permite demostrar las fortalezasde este enfoque

The effect of the incidence function on the existence of backward bifurcation

<p>In modelling, the dynamics of infectious disease, the choice of the specific mathematical formulation of disease transmission (i.e. the incidence function) is one of the initial assumptions to be made. While inconsequential in many situations, we show that the incidence function can have an effect on the existence of backward bifurcation (the phenomenon where a disease can persist even when the basic reproductive number is less than 1). More specifically, we compare mass action (MA) and standard incidence (SI) (the most common incidence functions) versions of two hallmark models in the backward bifurcation literature and an original combination model. Our findings indicate that the SI formation of disease transmission is more conducive to backward bifurcation than MA, a trend seen in all the models analysed.</p

Using geospatial modelling to optimize the rollout of antiretroviral-based pre-exposure HIV interventions in Sub-Saharan Africa.

Antiretroviral (ARV)-based pre-exposure HIV interventions may soon be rolled out in resource-constrained Sub-Saharan African countries, but rollout plans have yet to be designed. Here we use geospatial modelling and optimization techniques to compare two rollout plans for ARV-based microbicides in South Africa: a utilitarian plan that minimizes incidence by using geographic targeting, and an egalitarian plan that maximizes geographic equity in access to interventions. We find significant geographic variation in the efficiency of interventions in reducing HIV transmission, and that efficiency increases disproportionately with increasing incidence. The utilitarian plan would result in considerable geographic inequity in access to interventions, but (by exploiting geographic variation in incidence) could prevent ~40% more infections than the egalitarian plan. Our results show that the geographic resource allocation decisions made at the beginning of a rollout, and the location where the rollout is initiated, will be crucial in determining the success of interventions in reducing HIV epidemics