Disease transmission on fragmented contact networks: livestock-associated Methicillin-resistant Staphylococcus aureus in the Danish pig-industry.
Animal trade in industrialised livestock-production systems creates a complex, heterogeneous, contact network that shapes between-herd transmission of infectious diseases. We report the results of a simple mathematical model that explores patterns of spread and persistence of livestock-associated Methicillin-resistant Staphylococcus aureus (LA-MRSA) in the Danish pig-industry associated with this trade network. Simulations show that LA-MRSA can become endemic sustained by animal movements alone. Despite the extremely low predicted endemic prevalence, eradication may be difficult, and decreasing within-farm prevalence, or the time it takes a LA-MRSA positive farm to recover a negative status, fails to break long-term persistence. Our results suggest that a low level of non-movement induced transmission strongly affects MRSA dynamics, increasing endemic prevalence and probability of persistence. We also compare the model-predicted risk of 291 individual farms becoming MRSA positive, with results from a recent Europe-wide survey of LA-MRSA in holdings with breeding pigs, and find a significant correlation between contact-network connectivity properties and the model-estimated risk measure.
Centre for Immunity, Infection and Evolution, University of Edinburgh, King's Buildings, UK. Mariano.Ciccolini@ed.ac.uk
M
M
Ciccolini
J
J
Dahl
M E
ME
Chase-Topping
M E J
ME
Woolhouse
D000818:Animals; D002353:Carrier State / Q000453:epidemiology / Q000662:veterinary; D003132:Commerce; D003718:Denmark / Q000453:epidemiology; D007221:Industry; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008962:Models, Theoretical; D015995:Prevalence; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000635:transmission / Q000662:veterinary*; D034421:Sus scrofa; D013552:Swine; D013553:Swine Diseases / Q000635:transmission*