Preliminary characterization of North American Standardbred horse movements between racetracks using network analysis
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1
University of Guelph, Canada
Harness racing involving Standardbred horses is popular in North America. For such purposes, Standardbreds could travel long distances, which can also involve crossing international borders. Movement of animals is a frequent transmission pathway for many infectious diseases, particularly for diseases where incubation period is long and animals are infectious before clinical signs appear. Once on a racetrack, animals could be in close direct and indirect contact with some probability of transmitting infectious agents to other susceptible animals. Movement of animals between establishments, such as racetracks, is frequently evaluated using network analysis. Depending on the objective, specific network measures could serve to approximate possible outbreak size, or to identify important nodes in the network. The objective of this study was to characterize movements of horses actively involved in Standardbred racing in the USA and Canada during 2008 and explore its spatial and temporal characteristics.
The source population for this study were Standardbred horses who were registered to race in both the USA and Canada during the year 2008. From this source population, a sample of 1,970 horses was randomly selected and data on all of their participation in races in the year were collected. Hence, the original dataset contained unique horse identifier, the date when each race occurred, and the unique racetrack code for each race. This original dataset of individual race entries was then converted to a series of directed monthly networks between individual racetracks. The conversion was based on the date when an individual horse was recorded in two different race tracks. If the horse raced in the same month on different racetracks, then the direction of horse movement was between the racetrack with earlier date to the racetrack with the later date. Following the conversion to monthly networks, selected individual node (i.e., racetrack) parameters and network-level characteristics were obtained for each calendar month. Of particular interest was the size of the maximum strong and weak components and their development over time. Network analysis was conducted in R 3.5.1 using packages igraph and sna.
In total, there were 38,859 individual race entries involving the study population of 1,970 horses. The frequency by which individual horses were involved in this type of horse racing over the entire year was approximately uniformly distributed between a minimum of one race, and a maximum of 50 (median=20, IQR=19). Horses included in this study over the period of the entire year raced on 258 individual racetracks, and the number of race entries per individual racetrack showed right-skewed distribution (median=4, IQR=69). Average in- (and out-) degree and strength were generally higher between May and October than in the rest of the year, with highest mean values recorded in July and August. Maximum monthly in-degree was recorded in May. Maximum monthly out-degree ranged between a minimum of 6 and maximum of 14, which was recorded in several months during the summer. Maximum monthly in-strength and out-strength had peak values in October. The maximum monthly weak and strong components had the highest value in July.
In conclusion, descriptive network analysis confirms that, on average, the highest potential for disease transmission for Standardbred horses involved in harness racing in North America occurred in the summer months, particularly in July. Nonetheless, some measures that could be reflective of potential “infectivity” (e.g., out-strength), or potential “susceptibility” (e.g., in-strength) suggests that individual racetracks could be under increased risk during the month of October. The large proportion of the study population that could be involved in a potential outbreak (estimated through the size of the maximum weak and strong components) emphasizes the role of preventive measures, infection control measures and surveillance efforts that stakeholders involved in this type of racing should practice.
Acknowledgements
We are grateful to Standardbred Canada, Mississauga, Ontario, Canada, for providing data.
Keywords:
Standardbred,
horse,
Network analysis,
spatial,
Temporal,
Racetrack,
Harness racing
Conference:
GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data, Davis, United States, 8 Oct - 10 Oct, 2019.
Presentation Type:
Poster-session
Topic:
Spatial-explicit or spatio-temporal network analysis
Citation:
Poljak
Z,
Ajayi
T and
Physick-Sheard
P
(2019). Preliminary characterization of North American Standardbred horse movements between racetracks using network analysis.
Front. Vet. Sci.
Conference Abstract:
GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data.
doi: 10.3389/conf.fvets.2019.05.00070
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Received:
20 Jun 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Dr. Zvonimir Poljak, University of Guelph, Guelph, Canada, zpoljak@ovc.uoguelph.ca