Prevailing Over PRRS
Monte Moss, DVM, is a realist. He knows that with 110,000 pigs being finished within a six-mile radius of his northern Indiana hog farm, he will never be “home free” when it comes to security against outbreaks of porcine reproductive and respiratory syndrome (PRRS).
Monte Moss, DVM, is a realist. He knows that with 110,000 pigs being finished within a six-mile radius of his northern Indiana hog farm, he will never be “home free” when it comes to security against outbreaks of porcine reproductive and respiratory syndrome (PRRS).
“Even if your farm is filtered, we have so much PRRS around us that we will always be at high risk. But we are getting more confident month by month that the filtration system we have installed is working and keeping the herd clean,” says the Burnettsville, IN, producer.
Moss’ 1,200-sow operation has gone 36 months without a PRRS break in his sow herd. He rents one remote finishing site that is PRRS-negative and owns one finishing site, located just a half mile from the sow farm, which is PRRS-positive. “We are weaning negative pigs and have done so for a couple of years,” he says.
Isolation Doesn’t Hold
Ten years ago, Moss envisioned that his far northern corner of White County, IN, would stay pretty well isolated with just his and a neighbor’s 1,200-sow operation, 3½ miles southwest, making up the only swine operations in the area.
But it wasn’t in the cards. Over the last 12 years or so, close to two dozen primarily wean-to-finish operations have cropped up across the landscape adjacent to Moss Farms. And a number of them have brought PRRS along with increased pig numbers (Figure 1).
To combat this potential disease threat, Moss tightened biosecurity protocols. Thinking that the virus was coming in by trucks, he built a truck wash and required his trucks to be washed between every load of weaned pigs or market hogs.
Rendering trucks were eliminated and a composting site was constructed. The sow unit became totally shower-in, shower-out and had designated employees, trucks and tools not shared with any other site.
All those efforts didn’t stop PRRS. “We’ve had PRRS a lot of times. We have been breaking an average of once a year since 2000, but since 2003, the PRRS breaks started getting more severe,” he recalls.
In 2008, two virulent strains of PRRS struck the sow farm just four months apart, causing over 300 abortions and 10% sow deaths as well as 25% death loss in the nursery. Both breaks occurred about three weeks after weaned pigs were imported into a finishing site two miles west of Moss’s sow farm.
“I threw up my hands and said I am quitting. I am done. I can’t raise pigs here because nobody is going to buy our pigs. We were a discouraged bunch of people,” Moss says.
Becoming PRRS-Free
But Moss was intrigued by PRRS air filtration work in Minnesota and decided it was worth a try. During the summer of 2009, Moss and his staff depopulated the sow herd and began installing an air filtration system, one of the first to be installed in a commercial sow unit in the United States. Before it was completed in October 2009, the sow farm broke with PRRS again.
“We were thinking we’ve spent all this money on filtration and we’ve already broken with PRRS. But we weren’t totally finished with construction and so we were not totally filtered when we broke. Since then, we think we’ve shown that it works,” he says. “It’s given us the best production we’ve ever had.” Moss Farms has improved from producing 23.5 pigs/sow/year (p/s/y) to about 27 p/s/y. Finishing performance has also been good, he says.
PRRS has continued to pummel finishing sites in northern Indiana. But Moss’ sow farm has stayed free of the virus, based on rope tests and blood work performed by Max Rodibaugh, DVM, Swine Health Services, Frankfort, IN. Tests indicate the sow herd is now officially PRRS naïve (all PRRS-positive sows are gone). Pigs are tested every 30 days by polymerase chain reaction (PCR). Groups of 240 multi-age, negative gilts are isolated, acclimated and tested by PCR for PRRS to assure negative status before being introduced into the herd 2-3 times a year. No vaccine has been used to avoid all PRRS titers.
One group of 240 gilts caused quite a scare in October 2010 when they were tested seven days post-arrival and turned up PCR positive for PRRS. “The filtered isolation barn is just 140 ft. from our gestation barn. We were dazed,” Moss recalls. “But we sold all of those gilts and stayed negative.”
In early November 2011, an 8,000-head finisher just two miles southwest of Moss was filled with weaned pigs from an infected sow herd. In late November 2011, a 2,000-head finisher two miles west of Moss broke with PRRS. The Moss sow farm survived both of those PRRS outbreaks.
Moving to Filtration
Moss minces no words when he says he believes that his decade-plus troubles with PRRS can be traced back to aerosol transmission of the virus.
“In my opinion, I think 95% or more of PRRS transmission is by aerosol. That means as an industry we are spending 95% to 100% of our biosecurity efforts on 5% of the problem in this industry. If we are really serious about biosecurity and stopping PRRS, then aerosol and filtration are what we need to look at,” he declares.
Moss says evidence indicates there are very few PRRS breaks in June through August. Plus, he prefers to tunnel-ventilate the sow barns during those hot months. “If I did filter 100% year ’round in the sow units, I felt like we would give up the effectiveness of our tunnel ventilation. So I decided to use a bail-out system in summer.”
Basically, the difference between a total air filtration system and a bail-out system is that with 100% filtration no outside air is allowed into the building that is not filtered — 12 months of the year, 365 days a year.