Risk assessment and cost-effectiveness analysis of Aujeszky's disease virus introduction through breeding and fattening pig movements into Spain

Movement of infected animals is considered the most likely route of Aujeszky's disease virus (ADV) introduction into free areas and the main obstacle to eradicating Aujeszky's disease (AD) in those areas, which have achieved a low prevalence (>0 and ≤10%) status. For this reason, the Spanish AD control and eradication program has established measures to enhance security in animal movements in an attempt to protect areas with free or low prevalence status; however, no studies have quantified the effectiveness of the current or alternative ADV introduction prevention measures. We performed a probabilistic risk assessment and cost-effectiveness analysis, using Monte Carlo simulation, to evaluate the probability of introducing ADV-infected animals into free or low prevalence areas under the Spanish AD control and eradication program. We found the mean probability of introducing ADV-infected animals, when breeding pigs were quarantined but not tested prior to shipment, is likely (up to 21%), representing 13.6 times higher risk than when breeding pigs were tested prior to shipment. The strategy of testing pigs on fattening farms 15 days prior to shipment and using a sample size sufficient to detect a prevalence of 5% with a 95% of confidence, could reduce the probability of introducing ADV-infected animals by 91% with no additional cost. Similarly, testing pigs on breeding and fattening farms using a sample size sufficient to detect a prevalence of 1% with a 95% of confidence, could reduce the probability of introducing ADV-infected animals by 99%, but with an increased cost of 81%. Results reported in this study identify factors that contribute to risk of ADV introduction and should aid the control and eradication of AD in Spain.