Highly dynamic animal contact network and implications on disease transmission

Chen, Shi; White, Brad J.; Sanderson, Michael W.; Amrine, David E.; Ilany, Amiyaal; Lanzas, Cristina

The ANOVA and spectrum analysis focused on the number of contacts (network degree distribution) and did not reveal the internal structural change of the networks (e.g. correlation of two individual calves across two different hours). Thus a quadratic assignment procedure (QAP) was applied to further investigate the similarities between the networks in different hours in a day 25 . The QAP was designed to measure the structure similarity (e.g. nominal, ordinal, and interval associations, for both network topology and roles in individual node) between two networks with the same nodes (in our study, the same individual animals). The QAP was comprehensively applied between each pair of the networks in two different hours within the same day (total of 24 3 23/2 5 276 pairs per day). The entire day was divided into three different intervals based on number of contacts: low-contact intervals from 12 am to 5 am (at hourly interval, e.g. 12 am indicated 12 am to 1 am, and the same held thereafter); high-contact intervals during 8 am, 2 pm, and 8 pm; and the remaining hourly intervals were considered as having medium contact. The average percentage of similarity between low-contact intervals and other low-contact intervals (whenever P . 0.05 of QAPs) for all days across all three pens was calculated. The percentages of similarity between two high-contact intervals and between high-and low-contact intervals were also calculated. These results further measured and revealed the potential network structure change. To illustrate, the actual networks were plotted at four different hourly intervals in a given day (e.g., 2 am, 8 am, 2 pm, and 8 pm, corresponding to animal sleeping, feeding, and other social behaviors, on August 11, 2011, for each pen) for visualization of both temporal and individual heterogeneities.