Semi-annual report indicates progress combatting PRRSV

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Producers and veterinarians have reduced the impact of porcine reproductive and respiratory syndrome virus (PRRSV) by more than $83 million over the past 6 years, according to a semi-annual study conducted on behalf of the National Pork Board (NPB).

The annual incidence of PRRSV outbreaks has declined (Figure 1), and the loss of weaned pigs due to PRRSV declined by more than 25% as of October 2016 compared to 2010 baseline data, reported Derald Holtkamp, DVM, of Iowa State University.

To provide perspective, Holtkamp showed data comparing annual losses from PRRSV versus porcine epidemic diarrhea virus (PEDV). In 2010, PRRSV caused the loss of 8.3 million pigs weaned and 9.9 million pigs marketed. In contrast, PEDV caused losses of 4.7 million to 6.4 million pigs weaned and 4.7 million to 6.4 million pigs marketed in the year of peak losses following its arrival in the US in 2013.

“Even at its worse, PEDV still did less damage than PRRSV does year after year,” Holtkamp said.

NPB’S STRATEGIC PLAN

The PRRSV progress reports are provided as part of NPB’s strategic 2020 goal to reduce the annual economic impact of PRRSV by 20% (as adjusted for inflation and measured against baseline data).

In his presentation, Holtkamp said there were four factors used to determine the overall impact of PRRSV on the value of lost productivity:

• Herd distribution —the percentage of breeding females and growing pigs in PRRSV-affected and -unaffected herds
• Productivity —the productivity of breeding herds and growing pigs in PRRSV-affected herds compared to unaffected herds
• Prices and costs —pig prices, input prices and costs
• National herd inventory —the size of the national herd

The report does not include factors such as treatment costs or the impact of PRRSV on the supply of pork and market-hog prices, Holtkamp said.

BIGGEST CHALLENGE: DATA

Incorporated into the report is analysis of farm-production records from 64 US breeding herds with known PRRSV status and outbreak histories, he said, noting that pig, feed-ingredient and diet prices for the October 2016 update were higher than they were for the 2010 study. Breeding-female inventory and pigs marketed also increased in 2016 compared to 2010.

The more recent updates are based on less production data than the 2010 baseline data, he said, adding that obtaining production data is the biggest challenge faced regarding compilation of the PRRSV reports.

All the progress made regarding PRRSV, he said, has been due to reduced productivity losses in PRRSV-affected herds relative to unaffected herds. This was especially so in PRRSV-positive breeding herds that hadn’t experienced an outbreak for at least 12 months — a finding he theorized may be due to a shift from live-virus inoculation to the use of PRRSV vaccines as well as improvements in bio-management.

OPPPORTUNITIES FOR IMPROVEMENT

Holtkamp emphasized that progress regarding PRRSV has never followed a straight line, but he identified some opportunities for more strides forward.

The studies indicate the industry has favored PRRSV control instead of elimination in breeding herds. That’s resulted in fewer unaffected PRRSV herds, but further progress will require favoring elimination in the future, he said.

Progress will also require a further reduction in the incidence of PRRSV outbreaks and a continued focus on biosecurity. In addition, to achieve more PRRSV-negative pigs at placement, there needs to be an increased effort to stabilize sow farms, Holtkamp said.