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Modeling Ontario’s livestock population structure to study pathogen spread

Mathematical and simulation models are often used to simulate foreign animal disease outbreaks and best practices for control. However, simulation outcomes are sensitive to the population structure used.

Source: American Association of Swine Veterinarians
Infectious diseases in farmed animals have economic, social and health consequences. Foreign animal diseases of swine are of significant concern. Mathematical and simulation models are often used to simulate FAD outbreaks and best practices for control. However, simulation outcomes are sensitive to the population structure used. Within Canada, access to individual swine farm population data with which to parameterize models is a challenge because of privacy concerns. Researchers at the University of Guelph Ontario Veterinary College and the Ontario Ministry of Agriculture set out to develop a methodology to model the farmed swine population in Ontario, Canada, that could represent the existing population structure and improve the efficacy of simulation models.

The research team developed a swine population model based on the factors such as facilities supporting farm infrastructure, land availability, zoning and local regulations, and natural geographic barriers that could affect swine farming in Ontario. Assigned farm locations were equal to the swine farm density described in the 2011 Canadian Census of Agriculture.

Farms were then randomly assigned to farm types proportional to the existing swine herd types. Swine population models were then compared with a known database of swine farm locations in Ontario and found that the modeled population was representative of farm locations with a high accuracy (AUC: 0.91, Standard deviation: 0.02) suggesting that the algorithm generated a reasonable approximation of farm locations in Ontario.

Conclusion
In the absence of a readily accessible dataset providing details of the relative locations of swine farms in Ontario, development of a model livestock population that captures key characteristics of the true population structure while protecting privacy concerns is an important methodological advancement. This methodology will be useful for individuals interested in modeling the spread of pathogens between farms across a landscape and using these models to evaluate disease control strategies.

Salah Uddin Khan, Terri L. O’Sullivan, Zvonimir Poljak and Amy L. Greer, University of Guelph Ontario Veterinary College Department of Population Medicine; and Janet Alsop, Ontario Ministry of Agriculture, Food and Rural Affairs; Modeling Livestock Population Structure: A Geospatial Database for Ontario Swine Farms; BMC Vet Res. 2018 Jan 30;14(1):31. doi: 10.1186/s12917-018-1362-y. PMID: 29382338 DOI: 10.1186/s12917-018-1362-y          

This research is funded by the Natural Sciences and Engineering Research Council and the Canada Research Chairs Program.

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