Animal and human health: tackling uncertainty through participatory modelling and simulation

Zoonoses–infectious diseases communicable between animals and humans–, drug resistance and environmental pollution are now causing serious health problems worldwide. These problems are closely tied to global environmental and socio-economic changes and to the transformation of production systems at the territorial level. In this context, health management is becoming a complex issue: it needs to be addressed in close collaboration with the public veterinary health, agriculture and environment sectors. New uncertainties are emerging, and non- conventional actors are entering the scene along-side the decision-makers traditionally responsible for public health. The participatory modelling and simulation approach incorporates the diverse knowledge of all of these actors. It reveals uncertainties and teaches participants how to manage them, to make decisions and to share responsibility. It constitutes a practical solution to ensure health issues are better integrated into territorial planning policies

Modelling the Minsky triad: A framework to perform reflexive MandS studies

In this paper, we propose a general framework to evaluate models of systems that are ill defined, incompletely known, and furthermore, which cannot be experimented in real conditions, such as the economical systems at the country scale, epidemics (for obvious ethical reasons) or any natural disasters, for instance where human lives are the main issue. Our framework relies on the generic Marvin Minsky's definition of a model and its specification in the frame of the Theory of Modelling and Simulation, initiated by B.P. Zeigler. Such a dynamic system implementation of the Marvin Minsky's model definition, we called the Minsky triad model, enables to address original questions. The Minsky triad model is a coupled model composed of the model of a real system, the model of this later model, and, in between, the model of the user of the later model. We argue that the Minsky triad model is very promising as a framework to design and to evaluate decision support systems for crisis management. (Résumé d'auteur

Recursive simulation and experimental frame for multiscale simulation

In this paper, we present a formal and operational framework for multiscale modeling and simulation. We focus on scale transfer viewed as the coupling between two models of the same system, one at the microscopic scale and the other at the macroscopic scale. We consider that some parameters of the macroscopic model are the result of microscopic processes described in the microscopic model. The main idea is to use an "experimenter model" which performs experiments on the microscopic model during the simulation and compute these parameters in line. To formalize the experimental design of the experimenter model, we define an experimental frame of transfer based on Discret Event System Specification. As an example, we present a multi scale model in epidemiology.We specify it using our framework, and we implement and simulate it within the Virtual Laboratory Environment. Finally, we discus some of the scale transfer issues and how we want to use the developed framework to address them. (Résumé d'auteur

Cattle trade network in Madagascar highlands and Rift Valley fever virus circulation

In 2008-2009 a RVF outbreak occurred in the Anjozorobe area, a temperate and mountainous area of Madagascar highlands. A serological study conducted there in 2009 showed an IgG seroprevalence rate of 28%. Data analysis suggested a recurrent circulation of RVFV. The objectives of this study were to describe the cattle trade network in this area and analyze the link between network structure and RVFV circulation. Questionnaire survey among 386 breeders from 47 villages was carried out to collect trade data. Yearly village-level seroconversion rate was estimated in 2010 by testing 516 cattle negative in 2009. Association between the occurrence of seroconversion and network centrality parameters, distance to the nearest water point and 2009 seroprevalence level was tested. Due to the non-independence of the centrality parameters, a bootstrap procedure was used to assess the effects of the independent variables. Average village-level seroconversion was 7%, ranging from 0-20%. Two types of trading practice were observed: exchanges and buy/sale. The corresponding networks appeared both scale-free, and a significant but low correlation was observed between them. A negative association was observed between the occurrence of seroconversion in the village and the 2009 seroprevalence level, as well as the distance to the nearest water point. After RVFV introduction, vector-based transmission may support the within-village circulation. The node degree in the exchange network was positively linked with the occurrence of seroconversion. It was not the case for the buy/sale network. Both networks could thus have distinct roles in RVFV circulation. The exchanges network could be the support for RVFV introduction in villages, the buy/sale network being probably rather implicated in the introduction of RVFV in the area, from other parts of Madagascar. (Texte intégral

Risk-based surveillance of chicken diseases using poultry trader networks in Oromia Regional State, Ethiopia

Highly pathogenic avian diseases such as Newcastle disease and avian influenza have serious social and economic impact in developing countries, including Ethiopia. Live bird markets and poultry traders are known risk factors for the spread of these diseases. In Ethiopia, Oromia regional state is an active chicken breeding region and the live bird markets are located on the main poultry trade road to the capital city Addis Ababa. The networks of chicken movements between 29 shared markets in Oromia regional state were built for festive and non-festive seasons, using a 'trader questionnaire' survey. Five centrality indices, in-degree, out-degree, in-closeness, out-closeness and random-walk betweenness, were calculated and the markets were ordered according to these indices. The festive seasons did not appear to impact the network structure, implying no necessary change of surveillance and control policies during these periods, merely a strengthening due to an increased volume of traded chicken. Three markets emerged as central in the network, with different epidemiological roles. Our findings indicate that these three poultry markets would ideally be chosen in a risk-based type of surveillance system and in targeted control policies. (Texte intégral