The development and use of a PRRS risk assessment tool (PRA) for evaluating breeding herd PRRS risks has been previously described (1). The PRA database has been descriptively summarized (2), has been used to benchmark individual herd and production system risks against a national database (3), and has been used to assess the relationships between external introduction risks and PRRS-negative herd status sustainability (4). Here we describe the use of the PRA as a tool for monitoring year-to-year changes in the risk profile of a large production system as well as to compare subsets of farms within that production system.
Most of the 15 breeding herds in this production system for the three year assessment period scored below the database median for external introduction risk but above the database median for internal circulation risk. Over the three year evaluation period the production system recorded a decrease in both internal and external risk score, as well as a reduction in the average number and percent of herds reporting clinical PRRS outbreak. However, four farms that scored below the system average in 2005 (LOW) showed an increase in risk score in 2007 after an initial decrease in 2006. This is in contrast to four farms that scored above the system average in 2005 (HIGH) but showed reductions in risk score in both 2006 and 2007.
The association between a reduction in risk scores and a reduction in reported clinical outbreaks in the overall production system and initially higher risk farms is promising. The PRA can be a useful risk measurement tool in the overall PRRS management plan for pig production systems.
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