Efficient Interruption of Infection Chains by Targeted Removal of Central Holdings in an Animal Trade Network

Kathrin Büttner,Arne Traulsen,Joachim Krieter,Imke Traulsen,Yamir Moreno

doi:10.1371/journal.pone.0074292

Kathrin Büttner, Arne Traulsen + Show 3 more

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https://doi.org/10.1371/journal.pone.0074292

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Abstract

Centrality parameters in animal trade networks typically have right-skewed distributions, implying that these networks are highly resistant against the random removal of holdings, but vulnerable to the targeted removal of the most central holdings. In the present study, we analysed the structural changes of an animal trade network topology based on the targeted removal of holdings using specific centrality parameters in comparison to the random removal of holdings. Three different time periods were analysed: the three-year network, the yearly and the monthly networks. The aim of this study was to identify appropriate measures for the targeted removal, which lead to a rapid fragmentation of the network. Furthermore, the optimal combination of the removal of three holdings regardless of their centrality was identified. The results showed that centrality parameters based on ingoing trade contacts, e.g. in-degree, ingoing infection chain and ingoing closeness, were not suitable for a rapid fragmentation in all three time periods. More efficient was the removal based on parameters considering the outgoing trade contacts. In all networks, a maximum percentage of 7.0% (on average 5.2%) of the holdings had to be removed to reduce the size of the largest component by more than 75%. The smallest difference from the optimal combination for all three time periods was obtained by the removal based on out-degree with on average 1.4% removed holdings, followed by outgoing infection chain and outgoing closeness. The targeted removal using the betweenness centrality differed the most from the optimal combination in comparison to the other parameters which consider the outgoing trade contacts. Due to the pyramidal structure and the directed nature of the pork supply chain the most efficient interruption of the infection chain for all three time periods was obtained by using the targeted removal based on out-degree.

Highlights

In the last decade, tremendous theoretical advances have been made in epidemiology on networks [1,2,3,4]
In order to compare the procedure between the three time periods, a linear regression was performed to fit a slope of the median values calculated over all iterations for less than 50% of removed holdings (Table 2)
Number and proportion of removed holdings to reduce the size of the largest network component by more than 75% by targeted removal depending on the ranking of specific centrality parameters

Summary

Introduction

Tremendous theoretical advances have been made in epidemiology on networks [1,2,3,4]. This kind of network analysis has been increasingly applied to evaluate the risk of disease transmission through animal movements in the livestock industry. Most of these studies have focussed on analysing the structure of trade networks via animal movements and comparing trade networks of different time periods [9,10,11,12,13,14,15]. This individual is removed from the network This does prevent the animal from being infected, but it can interrupt the chain of infection such that a further spread to other animals is prevented [3]. It makes sense to remove highly central nodes first

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