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PRRS System Approach Checklist The “systems approach” Dr. John Waddell and those involved in the production system used to deal with PRRS in growing pigs included the following measures: • Mass vaccination at weaning (immediately upon arrival in the nursery). • Administration via needle-free syringe to reduce pig-to-pig transmission of field virus. • Monitoring of sow farms monthly for presence of PRRS virus circulation. • An aggressive preventive approach including Ingelvac PRRS ATP; HP One (H. parasuis bacterin); Mycoplasma hyopneumoniae vaccine; Lawsonia intracellularis (ileitis vaccine); and Ery ALC (Erysipelas). • Initiate biosecurity measures to reduce transmission of virus. Under biosecurity improvements: 1. Move all pigs in dedicated trucks from sow sites to transfer stations 2. Mortality removal process 3. Perimeter fencing/entry gating/signage 4. A All vehicles washed and “baked” 5. Biosecurity pyramid 6. A Attention to detail. New standard operating procedures were written and implemented across all sow and nursery sites. 7. PRRS Risk Assessments.

Nebraska swine practitioner John Waddell realized early on a battle against porcine reproductive and respiratory syndrome (PRRS) in the nursery would require a “systems approach.”

Three years and over a million vaccinated pigs later, he was right.

Performance data accumulated by the Sutton, Neb., veterinarian from mixed PRRSstatus herds dating back to 2005 showed an overwhelming benefit to vaccination and stepped-up biosecurity in a large, commercial farrow-to-finish system.

Pre-vaccination, sow farms providing pigs to the system were either PRRS negative, or naïve, or PRRS positive, both stable and unstable. Weaned pigs were sourced to nurseries based on PRRS status – pigs from positive farms went to positive nurseries and pigs from negative farms went to separate PRRS-negative nurseries in the three-site system.

Live, site-specific PRRS virus (serum) inoculation and temporary herd closure were utilized when breeding herds became unstable.

In the positive nurseries, PRRS seroconversion was predictable, occurring mid-late nursery with the expected disease and performance miseries. Negative nurseries were meeting production targets.

Waddell described mortality rates in the positive flows as out of control, averaging over 9 percent and spiking as high as 15 percent. The system, he said, was “severely broken.”

Their best recourse: Fast and furious vaccination of pigs at three weeks of age.

“The science was incontrovertible. In the growing pig model, the vaccine works,” noted Waddell. “We knew there were other issues, but PRRS was the primary initiating co-factor.”

Beginning in February of 2005, weaned pigs received a 2 mL dose of Ingelvac® PRRS ATP, a modified live product from Boehringer Ingelheim Vetmedica, Inc. (BIVI).

By the end of that first year, more than 300,000 vaccinated pigs from PRRS-positive nurseries had weight gain and feed efficiency as good as or better than negative pigs (see Table 1). And most striking, mortality dropped below 3 percent.

Results were so impressive that all nursery flows – more than 1 million pigs – were vaccinated over the next two years. Again, mortality and performance figures met targets (see Table 2). Another plus: By stabilizing all pigs with vaccine, flows could be commingled, adding valuable management flexibility, said Waddell. This meant shorter nursery filling times, narrow age spreads and streamlined transportation logistics.

According to the Nebraska practitioner, most current measures of PRRS control are targeted at breeding herds. However, recent reports from the National Pork Board and Iowa State University indicate that 88 percent of the costs associated with PRRS are incurred in growing pigs. Researchers put a $6 per head PRRS price tag on losses for pigs in the nursery phase.1

In the end, he believes a key to success of this all-inclusive approach to PRRS control is consistently inducing uniform immunity among vaccinated groups of pigs.

“Waddell’s case clearly shows the importance of vaccination in managing PRRS virus,” noted Reid Philips, DVM, BIVI technical manager for respiratory products.

Philips agrees that controlling the disease requires a systematic line of attack. “The use of vaccines, biosecurity, pig management and sanitation procedures, sow farm monitoring and PRRS risk assessments, are all important in a comprehensive scheme to control PRRS in growing pigs.” According to the BIVI technical manager, vaccine should be administered at least four weeks prior to field virus exposure for adequate development of protective immunity. In the study system, weaning groups periodically had PRRS PCR-positive piglets upon nursery entry, which compromised the goal of scheduling vaccination at least three to four weeks prior to field virus exposure.

The decision was made to vaccinate pigs upon nursery entry with needle-free syringe technology to minimize the risk of accelerating the spread of field virus from pig to pig. Spreading virus is a common problem in groups of positive pigs when vaccinated with traditional hypodermic needles, Waddell pointed out. This approach maximized the proportion of pigs provided opportunity to develop a protective vaccinal immune response prior to natural exposure.

Three years ago, desperate times called for desperate measures, recalled Waddell. “Today, owners of the system are convinced PRRS vaccine in positive flows is a necessity. Vaccination gave us the confidence to combine the flows when necessary.”

Reference:
1. Neuman E., et. al., JAVMA, 2005