Tracking socioeconomic vulnerability using network analysis: insights from an avian influenza outbreak in an ostrich production network.
BACKGROUND
The focus of management in many complex systems is shifting towards facilitation, adaptation, building resilience, and reducing vulnerability. Resilience management requires the development and application of general heuristics and methods for tracking changes in both resilience and vulnerability. We explored the emergence of vulnerability in the South African domestic ostrich industry, an animal production system which typically involves 3-4 movements of each bird during its lifetime. This system has experienced several disease outbreaks, and the aim of this study was to investigate whether these movements have contributed to the vulnerability of this system to large disease outbreaks.


RESULTS
The ostrich production system requires numerous movements of birds between different farm types associated with growth (i.e. Hatchery to juvenile rearing farm to adult rearing farm). We used 5 years of movement records between 2005 and 2011 prior to an outbreak of Highly Pathogenic Avian Influenza (H5N2). These data were analyzed using a network analysis in which the farms were represented as nodes and the movements of birds as links. We tested the hypothesis that increasing economic efficiency in the domestic ostrich industry in South Africa made the system more vulnerable to outbreak of Highly Pathogenic Avian Influenza (H5N2). Our results indicated that as time progressed, the network became increasingly vulnerable to pathogen outbreaks. The farms that became infected during the outbreak displayed network qualities, such as significantly higher connectivity and centrality, which predisposed them to be more vulnerable to disease outbreak.


CONCLUSIONS
Taken in the context of previous research, our results provide strong support for the application of network analysis to track vulnerability, while also providing useful practical implications for system monitoring and management.
Percy FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch, Cape Town, South Africa.
Christine
C
Moore
Percy FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch, Cape Town, South Africa.
Graeme S
GS
Cumming
South African Environmental Observation Network, Fynbos Node, Newlands, Cape Town, South Africa.
Jasper
J
Slingsby
Government of the Western Cape, Department of Agriculture, Elsenburg, South Africa.
John
J
Grewar
D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D000829:Animals, Domestic / Q000254:growth & development* / Q000821:virology; D003195:Computer Communication Networks; D004196:Disease Outbreaks / Q000517:prevention & control / Q000706:statistics & numerical data; D054884:Host-Pathogen Interactions; D053125:Influenza A Virus, H5N2 Subtype / Q000502:physiology; D005585:Influenza in Birds / Q000453:epidemiology / Q000821:virology; D012307:Risk Factors; D012621:Seasons; D013019:South Africa / Q000453:epidemiology; D020310:Struthioniformes / Q000254:growth & development* / Q000821:virology; D013997:Time Factors