Evaluation of Control Strategies for Porcine Reproductive and Respiratory Syndrome (PRRS) in Swine Breeding Herds Using a Discrete Event Agent-Based Model

PLoS One. 2016 Nov 22;11(11):e0166596. doi: 10.1371/journal.pone.0166596. eCollection 2016.

Abstract

The objective of this study was to develop a discrete event agent-based stochastic model to explore the likelihood of the occurrence of porcine reproductive and respiratory syndrome (PRRS) outbreaks in swine herds with different PRRS control measures in place. The control measures evaluated included vaccination with a modified-live attenuated vaccine and live-virus inoculation of gilts, and both were compared to a baseline scenario where no control measures were in place. A typical North American 1,000-sow farrow-to-wean swine herd was used as a model, with production and disease parameters estimated from the literature and expert opinion. The model constructed herein was not only able to capture individual animal heterogeneity in immunity to and shedding of the PRRS virus, but also the dynamic animal flow and contact structure typical in such herds under field conditions. The model outcomes included maximum number of females infected per simulation, and time at which that happened and the incidence of infected weaned piglets during the first year of challenge-virus introduction. Results showed that the baseline scenario produced a larger percentage of simulations resulting in outbreaks compared to the control scenarios, and interestingly some of the outbreaks occurred over long periods after virus introduction. The live-virus inoculation scenario showed promising results, with fewer simulations resulting in outbreaks than the other scenarios, but the negative impacts of maintaining a PRRS-positive population should be considered. Finally, under the assumptions of the current model, neither of the control strategies prevented the infection from spreading to the piglet population, which highlights the importance of maintaining internal biosecurity practices at the farrowing room level.

MeSH terms

  • Animals
  • Breeding*
  • Disease Outbreaks*
  • Female
  • Male
  • Models, Biological*
  • North America / epidemiology
  • Porcine Reproductive and Respiratory Syndrome / epidemiology*
  • Porcine Reproductive and Respiratory Syndrome / prevention & control*
  • Porcine respiratory and reproductive syndrome virus*
  • Swine / virology*

Grants and funding

Graduate student funding (A.G.A.) was provided by the Ontario Ministry of Agriculture, Food and Rural Affairs, the Natural Sciences and Engineering Research Council of Canada, and the Ontario Graduate Scholarship. This work was also supported by Ontario Ministry of Agriculture, Food and Rural Affairs grant number UofG2011-1031 to Zvonimir Poljak. These entities did not have any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.