Study on PRRS Focuses on Biosecurity Procedures that Make a Difference

The number of production events in facilities of all sizes and production styles had a direct impact on porcine reproductive and respiratory system (PRRS) outbreaks ( Swine Health Information Center )

In a recently completed study funded by the Swine Health Information Center (SHIC), Daniel Linhares, DVM, from Iowa State University (ISU), and his colleagues reported on the number of production events in facilities of all sizes and production styles that had a direct impact on porcine reproductive and respiratory system (PRRS) outbreaks to help prioritize biosecurity practices. The study also compared biosecurity practices of herds with relatively low or high PRRS incidence within and between production systems. Because of the significant sample size, the project provides concrete data to help producers allocating investment in biosecurity, minimizing the risk of virus introduction.

The objective was to describe key differences in the biosecurity aspects of breeding herds with relatively low PRRS incidence, compared to those with relatively high PRRS incidence, so ongoing biosecurity assessments can be more efficient and take less time. This was a collaborative project between ISU, the University of Minnesota, and swine production systems. It included 14 production systems and 84 herds in 13 states across the US.

“One of the findings is that the number of events matter,” Linhares remarked. For example, if a system weans pigs every day versus once a week, it makes a difference. The frequency of people exiting and re-entering the farm also has an effect. A higher number of events was associated with a higher frequency of PRRS outbreaks. While Linhares acknowledges operations cannot avoid the entry of pigs and people, he said the study suggests efforts to organize the people and pig flows to reduce events would be beneficial.

Linhares says that full, comprehensive biosecurity assessments are necessary to characterize all risks for a given pig population. In addition, the dataset from this study will allow identifying the minimum number of questions that, when combined, gives a good correlation with expected frequency of PRRS outbreaks. This would allow producers to measure farm vulnerability to disease introduction more frequently over time.

Biosecurity aspects of each breeding herd were assessed using a 346-question survey, developed by Derald Holtkamp, DVM, at ISU. The survey contained questions about herd demographics, area swine density, PRRS outbreak history, frequency of risk events, and biosecurity practices related to swine transport, people movement, carcass disposal, supply deliveries, and other events. Results of the surveys from high and low PRRS incident herds were compared.

High PRRS incident farms had a higher monthly frequency of people entering and exiting the farm, in addition to higher frequency of pig movements. On-farm rendering was the production practice having the largest difference in frequency between low versus high PRRS incidence farms. The study summary gives additional information about area density, downtime and other differences between the two groups.

The relative risk of PRRS outbreaks can be measured using “biosecurity scores” derived from questionnaires, Linhares said. Benchmarking the scores according to high impact outcomes, like those summarized in the report, may be a great tool for managers and producers to identify opportunities to reduce the vulnerability of their swine operations.