Implementation and validation of an economic module for the epidemiological model Be-FAST to predict the costs generated by livestock diseases epidemics. Application to the Classical Swine Fever case in Spain

Abstract Classical Swine Fever (CSF) is one of the most harmful livestock diseases for the economy of the swine sector worldwide. Specifically in Spain, the costs in the two last CSF outbreaks (1997 and 2001) have been estimated above 108 million euros. In this work, we aim to evaluate the economic impact of important livestock disease epidemics, and particularly the CSF in Spain. This study starts with a preliminary classification of the costs associated with CSF epidemics. In order to estimate the expected costs of a given epidemic in a considered area, a new economic module has been integrated into the epidemiological model Be-FAST, a time-spatial stochastic spread mathematical model for studying the transmission of diseases within and between farms. The input data for economic parameters have been obtained from entities related with the swine industry in Spain. The new Be-FAST module is tested by comparing the results obtained with historical data from CSF epidemics in Spain. The outcomes show that severe CSF epidemics also have a strong economic impact with around 80% of the costs related to animal culling, while costs associated with control measures are directly associated with the number of infected farms and the duration of the epidemic. The results presented in this work * Corresponding author: [email protected] 1 are expected to provide valuable information to decision makers, including animal health officials and insurance companies, and can be extended to other livestock diseases or used to predict the economic impact of future outbreaks

Be-CoDiS: A mathematical model to predict the risk of human diseases spread between countries. Validation and application to the 2014-15 Ebola Virus Disease epidemic

Ebola virus disease is a lethal human and primate disease that currently requires a particular attention from the international health authorities due to important outbreaks in some Western African countries and isolated cases in the United Kingdom, the USA and Spain. Regarding the emergency of this situation, there is a need of development of decision tools, such as mathematical models, to assist the authorities to focus their efforts in important factors to eradicate Ebola. In this work, we propose a novel deterministic spatial-temporal model, called Be-CoDiS (Between-Countries Disease Spread), to study the evolution of human diseases within and between countries. The main interesting characteristics of Be-CoDiS are the consideration of the movement of people between countries, the control measure effects and the use of time dependent coefficients adapted to each country. First, we focus on the mathematical formulation of each component of the model and explain how its parameters and inputs are obtained. Then, in order to validate our approach, we consider two numerical experiments regarding the 2014-15 Ebola epidemic. The first one studies the ability of the model in predicting the EVD evolution between countries starting from the index cases in Guinea in December 2013. The second one consists of forecasting the evolution of the epidemic by using some recent data. The results obtained with Be-CoDiS are compared to real data and other models outputs found in the literature. Finally, a brief parameter sensitivity analysis is done. A free Matlab version of Be-CoDiS is available at: http://www.mat.ucm.es/momat/software.htmComment: 34 pages; Version 5; Work in Progres

Regional strategy for the control of African swine fever in Africa

The actual African evolution is characterized by a strong integration at regional level, resulting in intensive trade, accentuated the movements of people and free movement of goods and people. In this context, only a regional approach can be considered for reducing the risk of economic losses due to the ASF. This approach creates synergy between countries and benefits from the experience of each other. Despite the loss due to the disease and many actions taken to control the disease, the situation remains dramatic in terms of threat of livelihood of populations. The elaborated strategy joined with an action plan, allow a progressive and coordinated control of the disease at regional level. To achieve this objective, it prioritizes the strengthening of capacities of technical services and the improvement of current production systems, creating optimal conditions for the modernization and development of the pig industry in a healthy context

Mechanisms of Avian Influenza virus transmission between farms: combining data collection and mathematical modelling

The lack of sufficient knowledge on the mechanisms of between-farm spread of livestock diseases hampers the development of much needed effective and fast control strategies. Some of the mechanisms responsible for pathogen spread can be deduced from epidemic tracing reports and literature while others can only be hypothesized from findings of studies on daily farm practices throughout the production round. For outbreaks without known/traced transmission routes, the concept of ‘neighbourhood’ infection is often adopted. This concept was founded based on the distance-dependence of the transmission risk with geographical proximity to an infectious farm being the key determinant of risk. Mathematical modelling plays an important role in obtaining quantitative insights into the contributions of the different mechanisms to disease spread. This can be by ranking the contributions of the individual transmission routes and/or obtaining a generic distance-dependent transmission risk. The models can guide the design of control strategies by providing a means to assess the efficacy of intervention strategies. In this thesis, modelling was used to assess the contributions of the wind-borne route and the other (traced) between-farm contacts to the transmission of highly pathogenic avian influenza during an epidemic in the Netherlands in 2003. It was found that these two routes together could only explain approximately 31% of the infections/cases. Visits by epidemic control teams were the least risky indicating the effectiveness of their biosecurity protocols in preventing transmission. New data on day-to-day farm practices and farmer opinion was collected in an attempt to generate hypotheses on transmission pathways and mechanisms that were yet to be appreciated. Indeed relevant unappreciated practices were found. They include irregularities in compliance to biosecurity as well as a broad category of neighbourhood-related risks. A new modelling approach to study neighbourhood transmission was developed guided by indirect transmission experiments. It involves the approximation of the pathogen dispersal process by a diffusive transport mechanism. Applying this diffusion model to the outbreak data of 2003, it was found that assuming delayed transmission, as opposed to instantaneous transmission, is an important phenomenon to be considered when modelling disease spread between locations. This modelling approach has the added advantage of availing an opportunity to assess the performance of intervention strategies without detailed mechanism-specific information. </p

Seasonality and adaptive dynamics in host-parasite systems in wildlife

I parametri ecologici sono solitamente difficili da stimare nella fauna selvatica, ma, nel caso di malattie infettive, il tasso di trasmissione del patogeno è il processo più complesso da valutare. Tra i tratti caratteristici dell’ospite la taglia corporea è sicuramente il più influente, in quanto molti parametri demografici scalano allometricamente con essa. In questo lavoro ho mostrato come le relazioni allometriche possono legare la taglia dell’ospite al tasso di trasmissione della malattia e al suo tasso netto di riproduzione. Quindi ho analizzato come le dinamiche epidemiologiche variano in funzione della taglia. Inoltre, sotto le stesse ipotesi, ho studiato l’effetto della variazione stagionale di parametri come tasso di trasmissione e natalità, sulla dinamica della malattia. Per quanto riguarda il controllo dell’infezione, ho analizzato l’effetto di politiche di abbattimento in diverse condizioni ecologiche. In particolare, mi sono concentrato sull’efficacia del controllo in presenza di ceppi a diversa virulenza e in presenza di struttura d’età nella popolazione ospite. In entrambi i casi ho trovato che esistono determinate condizioni ecologiche per cui una politica di eradicazione della malattia basata sull’abbattimento può avere conseguenze peggiori dell’alternativa zero. Ho inoltre mostrato in quali condizioni semplici politiche di abbattimento tempo-variante possono migliorare significativamente il controllo della malattia.Ecological parameters are usually hard to estimate correctly in wild populations, but, in the case of infectious diseases, the rate of transmission of the pathogen agent is often the most complex process to evaluate. Of the many traits characterizing host species demography, body size is probably the most influential one, as many demographic parameters scale allometrically with host body size. In this work I show how the allometric relationships, usually found for demographic parameters, may link host body size with the disease transmission rate and its basic reproduction number. Then, I analysed the effect of seasonal variation in different ecological and epidemiological parameters on disease dynamics. Under the point of view of disease control, I analysed the effectiveness of depopulation policies in different ecological conditions. In particular, I focused on control effectiveness when strains with different virulence co-circulate in the host population and when disease transmission is a function of the age/stage class of the host individuals. In both cases, I found that (under certain conditions) culling policies may perform worse, in terms of disease control, than the do-nothing alternative. I also show in which conditions simple time-variant control policies can improve disease control in wildlife