Network analysis of pig movements in Argentina: identification of key farms in the spread of diseases and relationship with their biosecurity level

ALARCÓN, LAURA V.; PERFUMO, C.; CIPRIOTTI, P.A.; MATEU, E.; MONTERUBBIANESI, M.; ALLEPUZ, A.

Conferencia; GeoVet 2019 ?Novel spatio-temporal approaches in the era of Big Data"; 2019

The present study analyzed the movements of pigs among commercial farms inArgentina with the aim to understand how they could contribute to the spread of a highly infectious disease upon its introduction. We also aimed to analyze the role of super-spreader farms in relation to their biosecurity. Pig movements data of Argentina for the 2014-2017 period were grouped in: animals of high genetic value sent to other farms (i.e. genetic), movements to or from markets and movements to finisher operations. Descriptive, centrality and cohesion measures were calculated for each type of movement and year. Next, to determine if the networks had a small-world topology the average path length and the clustering coefficients were compared with the results of random Erdős?Rényi network simulations. Finally, the R 0 of the genetic network was calculated and its reduction was assessed by removing highly connected farms. Farms whose elimination resulted in a reduction of 90% on R 0 where considered as super-spreaders and their external biosecurity score was evaluated. The threeanalyzed networks followed a power-law distribution (i.e. few nodes accounted for most of the movements) and the genetic network had a remarkable small world topology. Therefore, a disease would spread fast if arriving to a highly connected farm and will be unlikely contained within small groups. In the genetic network, thirty-one farms were identified as super-spreaders for all years, while other 55 were super-spreaders at least one year from an average of 1613 farms/year here analyzed. Removal of less than 5% of the farms resulted in a >90% reduction of R0 indicating that just few farms would have a key role in the spread of diseases. When the biosecurity scores of them wereexamined it was evident that many farms were at risk of introducing and disseminating new pathogens because of its limited external biosecurity. Results allowed to identify which farms have a high potential for disease spread through animal movements. Those farms are targets for prevention and intervention actions. Results also emphasize the need for increasing the biosecurity of those critical farms.