Porcine Reproductive and Respiratory Syndrome (PRRS) continues to be a major issue on North American farms, however the coordinated application of several key tools against PRRS has been shown to have a dramatic impact on reducing the losses of both pigs and profits. At a meeting in Chicago this winter, Dale Polson, DVM PhD, reported on a PRRS pilot control/eradication project and discussed their applicability to area/regional control projects.

Dr Polson began his presentation with two premises, "Premise One: Complementary methods, when applied together, reduce wild-type virus circulation within and among populations, and are essential for management of PRRS at an area/regional level."

"Premise Two: The most effective utilization of these methods requires a higher degree of cooperation, coordination and collaboration than is the norm across our industry," he continued.

The 'Plan A' objective of the pilot project was to eliminate the virus. In this pilot study, there were two distinct areas and a total of 22 sow farms (33,000 sows), two isolation sites, one boar stud, 88 wean-to-finish barns, 12 nursery barns, 154 finisher barns and one feed mill.

To put the project in perspective, two previous depopulation - repopulation attempts to eliminate the virus had been unsuccessful. In addition, system performance was poor and the system was for sale. There was little to no confidence in the efficacy of available PRRS vaccines, however the owners were willing to try to control/eliminate the virus with a multi-faceted, collaborative approach.

Dr Polson notes there are five steps to PRRS health management:

1. identify goals
2. determine current status
3. understand current constraints (including PRRS risks)
4. outline, select and implement a PRRS management option, and
5. measure and monitor progress.

"It's all about the plan, the team, the method and the tools," he says. In the previous pilot project, he believes a number of risk factors contributed to the compromise of the elimination goal. These included:

• Undersized ISO/acclimation and “production anxiety” led to unplanned and premature opening of the system to naïve gilt introduction
• Naïve gilts entered the system when animals at other system sites were still circulating the virus
• Limitations in internal biosecurity led to spread among the newly introduced gilts, and from there, spread throughout the system
• Challenges related to the level of commitment to the program and to key components of the program.

A new 'Plan B', supporting a revised goal of PRRS control, was developed and implemented to help address the previous issues, according to Dr Polson. The new objectives included:

• Increase pigs marketed throughput (increase sow herd weaned pig output and increase and maintain nursery-finishing livability)
• Achieve and maintain sow herd PRRS stability
• Pursue sow herd restructuring (reach and sustain targeted inventory and re-establish mature normal parity structure)

"In spite of the issues which affected the pursuit of the original goal of system PRRS virus elimination, this system documented significant improvements in pig and economic performance," noted Dr Polson.

"The 'Plan B' project continued to establish parity-segregated gilt/sow flow and utilize a form of area-segregated 'all in/all out' flow. The system also vaccinated for PRRS: replacement gilts twice with the modified live virus vaccine 30 days apart; sow herds mass-vaccinated four times per year (and also, on occasion, sow farms are contingent-vaccinated upon detected viral circulation in due-to-wean piglets). We double vaccinated pigs at seven and 37 days post-weaning when elimination was the goal, but eventually changed to a single growing pig vaccination when the goal changed to control."

Dr Polson says the system's efforts paid off. Weaned pig output and growing pig livability improved and the throughput of pigs marketed improved. Most importantly, the benefit/cost ratio has been positive.

Farms.com noted that the commentary is sponsored by Boehringer-Ingelheim Vetmedica, Inc. Acknowledgement for the information presented by Dr Polson goes to Butch Baker, Greg Hartsook, Reid Philips and Scott Dee.

February 2009

Further Reading

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Find out more information on Porcine Reproductive Respiratory Syndrome (PRRS) by clicking here.