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Combining nursery pigs from different sources can present several challenges to managers of grow-finish farms, the most problematic being the spread of orcine reproductive and respiratory syndrome (PRRS) from infected pigs to healthy ones. For Nebraska veterinarian John Waddell, preventing this meant constantly monitoring sow farms and pig sources and managing throughput timing and flows to segregate positive and negative pigs.

In other words, it was a little luck and a lot of work.

As consultant for a large Midwestern system, the Sutton, Neb., practitioner now uses PRRS vaccine as an insurance policy for commingled pigs coming into nurseries from all flows.

“We couldn’t predict which sow farms would remain stable or become slightly unstable and produce viremic pigs,” Waddell explains. “So there was always a risk of mixing pigs of different status, PRRS infection and significant production losses.”

In late 2005, Waddell began to vaccinate all pigs flowing in from the commercial sow farms – over half a million pigs per year.

“Vaccinating all the pigs for PRRS allowed us to combine pigs from different sow farms, which eliminated a lot of headaches,” Waddell says. “Our experience has shown us how effective the vaccine is in providing immunity and we’re confident that it’s an important disease management tool in situations where pigs from
different flows are combined.

“Now we’re filling nurseries and finishers faster, maintaining better age segregation and improving production efficiency.”

Today, pigs are weaned at three weeks of age and vaccinated with one full dose of Ingelvac® PRRS ATP vaccine.

As a result of implementing the PRRS vaccination program, Waddell says nursery mortality rates have dropped from double digits in early 2005 to an average well below two percent. “We’ve seen a dramatic response to vaccination both in the nursery and into the finisher,” he adds.

Timing of immunization of course, is critical to efficacy of the PRRS vaccine. Pigs should be vaccinated at least four weeks before exposure to field virus, states Waddell. “The window is pretty tight if pigs are exposed in the nursery and vaccinated upon entry. In any given group, there is potential for some leaker pigs to be weaned into the population, but appropriate immunization can certainly help reduce disease episodes in the nursery.”

Despite the disease interventions in the nursery and finisher, Waddell says they have not been able to stop PRRS completely in the sow farms. “PRRS breaks still occur and we don’t always catch them when they start to leak virus. That makes pig vaccination all the more important,” he emphasizes.

Impact of PRRS on PCVAD

Recent industry research has shown a correlation between PRRS and other diseases, and prevalence of porcine circovirus associated disease (PCVAD) caused by circovirus type 2 (PCV2).

Another huge piece of the disease puzzle in nurseries and finishers is the role of circovirus, notes Dr. Waddell.

“In our system, we vaccinate for ileitis, Salmonella choleraesuis and Mycoplasma,” Waddell adds. “We have not experienced any severe circovirus-related cases, so we’re wondering, and this is speculation, if doing a good job controlling cofactors like PRRS, mycoplasma and salmonella helps to prevent the devastating effects of circovirus associated disease.”

Backing that theory is a program Boehringer Ingelheim Vetmedica, Inc. called MAGIC – Monitoring Assignment for Global Infection with Circovirus.

Through the MAGIC program, BIVI can help the industry more accurately identify on-farm disease risks associated with PCVAD. Each MAGIC survey is used to assess several disease risk factors related to PCVAD and to establish an accurate benchmark for other disease cofactors like PRRS. Because circovirus-induced diseases are most often dependent on the presence of other diseases such as PRRS, it is important to conduct a complete disease assessment.

According to John Kolb, DVM, technical manager for BIVI, 58 farms participated in MAGIC, all with evidence of clinical PCVAD. Although all the data has not been analyzed, the in-depth investigation puts some validity behind Waddell’s speculation: PRRS virus was a primary infectious cofactor in herds struggling with PCVAD.

Waddell is currently testing circovirus vaccine – a precious commodity these days due to short supply – and he is curious if it will affect grow- finish mortality. “Even though our rate is not high, we wonder if we can drop death rate another two percent, which would be significant.

“As the industry enters a period of shrinking profits due to high corn prices, many immune management tools we’ve depended on will face scrutiny from a cost/benefit standpoint,” he says.

“The PRRS vaccine, however, is possibly the last vaccine we’d pull. And considering the success and effectiveness of the ileitis and mycoplasma vaccines, that says a lot.”