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KMID : 1094020160330050278
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Journal of Veterinary Clinics
2016 Volume.33 No. 5 p.278 ~ p.285
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Properties of a Social Network Topology of Livestock Movements to Slaughterhouse in Korea
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Park Hyuk
Pak Son-Il
Bae Sun-Hak
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Abstract
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Epidemiological studies have shown the association between transportation of live animals and the potentialtransmission of infectious disease between premises. This finding was also observed in the 2014-2015 foot-and-mouthdisease (FMD) outbreak in Korea. Furthermore, slaughterhouses played a key role in the global spread of the FMDvirus during the epidemic. In this context, in-depth knowledge of the structure of direct and indirect contact betweenslaughterhouses is paramount for understanding the dynamics of FMD transmission. But the social network structureof vehicle movements to slaughterhouses in Korea remains unclear. Hence, the aim of this study was to configurea social network topology of vehicle movements between slaughterhouses for a better understanding of how they arepotentially connected, and to explore whether FMD outbreaks can be explained by the network properties constructedin the study. We created five monthly directed networks based on the frequency and chronology of on- and offslaughterhousevehicle movements. For the monthly network, a node represented a slaughterhouse, and an edge (orlink) denoted vehicle movement between two slaughterhouses. Movement data were retrieved from the national KoreanAnimal Health Integrated System (KAHIS) database, which tracks the routes of individual vehicle movements usinga global positioning system (GPS). Electronic registration of livestock movements has been a mandatory requirementsince 2013 to ensure traceability of such movements. For each of the five studied networks, the network structureswere characterized by small-world properties, with a short mean distance, a high clustering coefficient, and a shortdiameter. In addition, a strongly connected component was observed in each of the created networks, and this giantcomponent included 94.4% to 100% of all network nodes. The characteristic hub-and-spoke type of structure wasnot identified. Such a structural vulnerability in the network suggests that once an infectious disease (such as FMD)is introduced in a random slaughterhouse within the cohesive component, it can spread to every other slaughterhousein the component. From an epidemiological perspective, for disease management, empirically derived small-worldnetworks could inform decision-makers on the higher potential for a large FMD epidemic within the livestock industry,and could provide insights into the rapid-transmission dynamics of the disease across long distances, despite a standstillof animal movements during the epidemic, given a single incursion of infection in any slaughterhouse in the country.
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KEYWORD
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social network, small-world, livestock movement, slaughterhouse
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