In a three-year research project in a large Nebraska swine operation, modified-live PRRS (porcine reproductive and respiratory syndrome) virus vaccine produced a positive reduction of nursery mortality and vastly improved production efficiency, says John Waddell, DVM, Sutton, NE.

The results showed that nursery pig vaccination pays. “PRRS continues to be a major challenge for U.S. swine producers, costing them more than $13/head for losses through the nursery and grow-finish phases,” he says.

Persistent PRRS Infection

There was no doubt that this operation endured a stiff PRRS challenge, says Waddell. Infected sows would regularly transfer viral infection to piglets. Seventeen-day-old weaned pigs would create multiple PRRS-positive nurseries containing unpredictable “leaker litters” that would then pass the virus 3-4 weeks post-arrival. Virtually all of the penmates would eventually become infected.

Double-digit nursery mortality and poor performance would characteristically last through the finishing phase, he says. In contrast, PRRS-negative nurseries that came from stable or naïve sow farms in the system produced mortality under 2%.

Challenging Nursery Problems

“When we first started this project in the nurseries in early 2005, there was actually kind of a defeatist attitude among a lot of the nursery managers,” Waddell recalls. The three-site, commercial system featured nursery pigs of mixed-health status, flowing from PRRS-negative and PRRS-positive stable and unstable sow herds. Average nursery pig mortality in the first year of the trial was greater than 9%. Vaccinating for PRRS reduced mortality to under 3%.

In the 2005 study, more than 600,000 pigs weaned from PRRS-positive herds were vaccinated.

Table 1 illustrates the dramatic results. PRRS-positive nurseries averaged mortality rates of 10.65%, which dropped to 2.65% with vaccine intervention. That compares favorably with PRRS-negative, non-vaccinated nurseries that recorded mortality rates of 3.04%. Performance data were similar in both groups, he explains.

“Vaccinated, PRRS-positive pigs performed equally well compared to our PRRS-negative pigs,” Waddell reported at World Pork Expo in Des Moines, IA. “We were excited that the PRRS vaccine really did control several strains of the PRRS virus.” The vaccine used throughout the trials was Boehringer Ingelheim's ATP PRRS vaccine. The PRRS vaccine was not used in negative and stable pig flows to allow for comparison. No sows were ever vaccinated.

Trial Results Sustained

In 2006-2007, all nursery pigs (513,797 from both PRRS-positive and PRRS-negative sow herds) were vaccinated for PRRS and mortality and performance evaluations were completed. The results revealed that the performance improvements achieved in 2005 were sustained through 2006-2007, says Waddell. The results are reported in Table 2.

Equally important, vaccinating all nursery pigs to achieve the same PRRS status offered much greater flexibility in pig flow management by permitting commingling of pigs from more sources, he explains. It also reduced nursery flow times and streamlined transportation logistics.

Controlling the PRRS virus in multiple nurseries and finishers has helped make the vaccine strain the dominant strain in that production system, Waddell says, stressing that PRRS vaccine produced immediate results, which have continued to this day.

Vaccination Experiences

Waddell believes that the use of needle-less vaccination technology in all trials should receive some credit for the project's success, in that it helped eliminate potential spread of the field virus via needle use from pig to pig.

When weaned pigs were picked up for PRRS vaccination with the needle-less system, they were also usually vaccinated for Mycoplasmal pneumonia and sometimes for Haemophilus parasuis.

However, vaccinating for circovirus proved unnecessary, despite the fact that porcine circovirus type 2 was known to exist in the large production system. “In that grow-finish flow, we have never initiated circovirus vaccination, and I believe that by controlling PRRS, this important co-factor, it's allowed us to forego circovirus vaccination,” Waddell states.

Comprehensive Plan Needed

The Nebraska research study demonstrates the importance of vaccination in managing PRRS virus, “especially when the virus is a co-factor with porcine circovirus-associated disease,” says Reid Philips, DVM, technical manager for respiratory products at Boehringer Ingelheim Vetmedica, Inc. PRRS vaccination provided at least a 3.5:1 return on investment, he adds.

“Controlling PRRS is a challenging task. The use of vaccines, along with appropriate biosecurity, pig management and sanitation procedures, sow farm monitoring and PRRS risk assessments are important parts of a comprehensive herd health program,” he says.

Waddell notes the operation has also invested heavily in truck sanitation bays, trailer baking bays, dedicated trucks and creating a barrier between outer and inner sanctum trailers to protect the integrity of the loading chute.

Table 1. Performance of PRRS-Positive, Vaccinated Nurseries and PRRS-Negative Nurseries
Item Total number of pigs out Mortality (%) In wt. (lb.) Out wt. (lb.) ADG1 (lb.) FE2
PRRS-positive, vaccinated nurseries 331,462 2.65 13.73 54.94 0.89 1.56
PRRS-negative, non-vaccinated nurseries 337,810 3.04 13.61 54.01 0.88 1.62
1Average daily gain, 2Feed efficiency
Table 2. Sustained Performance of All Nursery Pig Flows, Both PRRS-Positive and PRRS-Negative, All Vaccinated
Item Total Pigs Out Mortality, (%) ADG1 (lb.) FE2
All Vaccinated Flows 1,053,886 1.99 0.84 1.64
1Average daily gain, 2Feed efficiency