By Chris Rademacher, Ana Paula Silva, Tina Peterson, Elisa De Conti, Giovani Trevisan, Gustavo Silva and Daniel Linhares, Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University College of Veterinary Medicine

Porcine reproductive and respiratory syndrome remains an elusive problem that continues to plague swine producers here in the United States and around the world. The most recent estimates indicate the cost of PRRS to the U.S. swine industry is $1.2 billion dollars annually and likely higher than that when the full impact of the most recent PRRS strains are factored in (Holtkamp and Osemeke, 2024).  Producers and veterinarians have been battling with this ever changing virus for over the past 30 years. While we have learned much about how to control and eliminate this virus from the breeding herds, there are many different protocols and techniques that have been developed over the years with variable and inconsistent results.

The PRRS Outbreak Management Program was developed as an epidemiological database to track PRRS outbreaks in breeding herds. The goal of the program is to evaluate different control and elimination practices during PRRS outbreak and how those practices impact three different outbreak recovery metrics. The POMP team has a confidentiality and data transfer agreement to streamline information transfer, while maintaining a high-level of data security. There is a survey tool that is used to collect the management practices, comprised of 5 major categories (Table 1). 

Survey information can be collected via connection with the POMP portal, an emailed Excel sheet, phone or in-person interview, or data transfer (any type of files can be received).  We are flexible and work with the producers and their veterinarians to collect the information in a way that is the most convenient for the participants. These practices are measured on how they impact three primary recovery metrics: Time to Stability, Time to Baseline Production and Total Losses per 1000 sows. TTS is the number of weeks it takes for the farm to produce 13 consecutive weeks of PRRSV PCR-negative pigs, per AASV definition. TTBP reflects the number of weeks for the farm to wean the same volume of piglets as prior to the outbreak. Total losses are defined as the number of lost weaned pigs between the outbreak and TTBP. This number of weaned pigs lost is adjusted to 1,000 sows, so that comparisons can be made between breeding herds of different sizes.

There are diagnostic testing costs incurred to determine Time to Stability and to characterize the virus (i.e., sequencing).  Whole PRRSV genome sequencing is another tool that POMP uses to help determine if the farm is infected with multiple viruses and what strains are involved. In an effort to defray some of these costs, Boehringer-Ingelheim covers up to $700 of diagnostic testing costs per outbreak. We have also received generous funding from the Iowa Pork Producers Association, which has also allowed us to assist producers with detailed PRRS genotyping. In the upcoming year, the POMP staff plans to begin the development of a benchmarking report for participating producers.  This report will allow them to compare themselves to other producers on key recovery metrics, including how different strains impact their ability to recover.  An interactive dashboard is also being built so that participants can query the database to answer any questions they may have.

To date, the POMP database has approximately 447 herd outbreaks from over 20 different producers. We need to continue to add current and historical outbreaks in order to continue to expand the statistical power of the analysis that can be derived from the database. Some of the preliminary information that has been discovered were recently shared at the PRRS Management Workshop, which is an annual summer meeting held in conjunction with the McKean ISU Swine Disease Conference and Iowa Swine Day.

Some preliminary analysis has demonstrated that there was a significant improvement in Time to Stability (25 weeks faster) for farms that are using batch farrowing compared to continuous farrowing. The batch farms also saw a 32% reduction in total losses when compared to continuous farrowing farms. This is most likely due to the fact that batch farrowing farms have all-in/all-out, compared to continuous farrowing farms. There may be a potential advantage to the consideration of using depopulation of the farrowing barn as an intervention strategy for weekly farrowing farms that are struggling to get back to stability. 

Other analyses revealed a significant advantage in TTS for farms using herd closure compared to those that did not.  Although the sample size was limited, there also appeared to be an advantage to using a combination of live virus inoculation and MLV in terms of achieving stability faster than using LVI alone. Consistent with previous industry reports, farms using MLV had less severe production impact compared to those using LVI or other forms of feedback.  Lastly, the impact of viral lineages varies on total losses, but certainly, the outbreaks with L1C.5 and L1C.2 are among the one with more severe losses as measured by TTBP and TL (Figure 1).

Figure 1

POMP is a useful tool for producers and veterinarians to harvest information from the PRRS outbreaks that the industry continues to suffer from.  We as an industry have the ability to learn together by participating in this program, in order to increase that analytical power of the results that come out.  The diagnostic cost offset and the analysis provided by the POMP team allows producers and veterinarians to make educated decisions about how to manage PRRS outbreaks and in the future, they will be able to benchmark their practices against others to see if there are areas of opportunity moving forward.  If you have interest in participating or learning more, you can access the POMP website or you can reach out to Rademacher at [email protected].

References

Holtkamp, D, and O Osemeke. 2024. “PRRS Now Costs Pork Producers $1.2 Billion per Year.” National Hog Farmer, July 30, 2024.