Through trial and error spanning more than 20 years, the pork industry has fought to get rid of the elusive porcine reproductive and respiratory syndrome (PRRS) virus. On-farm control programs have been improved, pilot regional control programs are expanding, and pork industry groups are beginning to build support for a grassroots effort to finally stamp out the costly virus.

As pork producers are coming to grips with two years of losses, they continue to search for ways to reduce costs in order to survive what may be another six months of red ink.

“If PRRS really costs us $560 million a year (an estimate from published data), and you look at all of the years since PRRS was first identified in the United States, it calculates out to about $11 billion that the industry has already paid for this disease. And in a $12-billion industry, that is like not being paid for producing any pigs for a year,” says Dale Polson, DVM, Boehringer Ingelheim Vetmedica, Inc. He estimates that the virus continues to cost the pork industry $1.5 million a day.

As bad as porcine circovirus-associated disease has been, it pales in comparison to PRRS losses, Polson comments. He estimates circovirus cost the pork industry $330-340 million per year at its peak.

Paul Yeske, DVM, Swine Vet Center (SVC), St. Peter, MN, says PRRS losses are staggering, but producers appear resigned to accept that there is no way out. Herd cleanup has been accomplished repeatedly and routinely and at relatively low cost, he says. “The problem is we've got herds breaking back at an alarming pace, especially in hog-dense areas. That has taken everyone's perspective away from cleanup because they believe they will just break back again, especially if they live in a pig-dense area,” he adds.

In a study done with the support of Boehringer Ingelheim Vetmedica, Inc., the Swine Vet Center followed 33 negative herds over 8½ years; 60% were still negative at one year following established negative, but at the end of 8½ years only 15% remained negative.

Yeske believes it's time to take a look at the bigger picture. Instead of living with those losses, it's time to invest in cleaning up PRRS to have a high-health industry. PRRS-negative status would lower the cost of production and “make the United States more price-competitive in the world protein market.”

True Cost of PRRS

According to Yeske, most PRRS breaks cost U.S. pork producers $200-250/sow.

To explain the cost and progression of the disease, Swine Vet Center's Laura Bruner, DVM, developed a fact sheet on management of a PRRS break and what to normally expect when it happens.

Documented losses stem from a PRRS break in a 1,500-sow farm in southern Minnesota, consulted by Swine Vet Center's Ross Kiehne, DVM. Figure 1 shows finishing pig cash flow by month (PRRS struck in November 2007) and how six months after the break when cash flow dipped (circled), the operation was in desperate need of cash.

“This is the biggest thing that hurt them, because they've got (PRRS) negative pigs coming out and a lot of pigs to feed. They've got a lot of expenses, but not a lot of income,” Bruner says. For this producer, the timing was worse because six months after the break (May 2008) corn prices were running $6-7/bu.

The 20 weeks of the PRRS break cost this producer about $182,000 in losses just on the sow side, or about $118/sow, Bruner says. Grow-finish mortality added another $97,000 in losses. If you factor in average daily gain and feed efficiency losses, you could easily tack on another $30,000, pushing the total loss on this farm to $309,000 or $201/sow.

Figure 2, Figure 3, Figure 4, and Figure 5 illustrate the performance on the 1,500-sow farm before, during and after the PRRS break, including total pigs weaned, percent stillborns, percent mummies and preweaning mortality, respectively.

Performance improves markedly in most categories after 12 weeks, but mummified births can last up to 16-20 weeks. Born alive dipped from 11.4 to 9.6 pigs/litter. Pig production during the 20-week period from November 2007 to March 2008 went from a norm of 637 pigs weaned/week, on average, to 442 pigs weaned/week, or $6,800/week loss based on a weaned pig cost of $35 and 196 fewer pigs/week. Overall, performance sank about 30%.

“Producers need to recognize that even though the pigs are getting better during the 20 weeks after the break, there is still reduced performance in average daily gain, feed efficiency and poorer starting pigs in the nursery and finisher,” Bruner says.

“Pigs may look better as more negative pigs are being produced, but you still have that population of positive pigs after the break that will infect the negative population of pigs that you are weaning. As long as you have one PRRS-positive pig, it is the same as having a whole group of positive pigs, because until you completely get rid of that virus and wean completely negative pigs, productivity will not return to pre-PRRS performance levels,” she states.

“A lot of times when you have a small population of PRRS-positive pigs, the negative pigs will not break with PRRS until the end of the nursery or the early finishing period, when it hits them hard, and when you have a lot of money already invested in them,” she points out.

And PRRS impedes the ability of the immune system to fight off common secondary bacteria, making Actinobacillus suis, Haemophilus parasuis, Mycoplasmal pneumonia and Streptococcus suis problems a lot worse.

Next Page: Air Filtration

The fact sheet Bruner developed lists six steps to help manage a PRRS break and what to expect:

  1. Diagnosis of PRRS involving testing and sequencing procedures.

  2. Exposure of all animals using natural exposure, direct virus delivery or commercial vaccine. The use of direct virus delivery or serum inoculation can basically clean up a PRRS break in just one turn of the barn (20 weeks) and has been used frequently in the Swine Vet Center practice because of its short duration and repeatability of results. It can shorten up the time to negative in some situations because it exposes all animals at the same time and eliminates that sub-population of animals that can make the virus linger on the farm longer.

    Commercial PRRS vaccine is also used to control virus spread and has been used quite successfully to vaccinate nursery pigs going into nurseries/wean-to-finishers in densely populated areas.

  3. Minimize virus circulation by closing the herd to incoming naïve animals for greater than 210 days, minimizing piglet movement in farrowing and not holding back smaller pigs at weaning that contain a lot of virus. Monitor virus circulation by monthly testing of 30 poor piglets out of older farrowing rooms using polymerase chain reaction.

  4. Minimize secondary bacteria using antibiotics, injectable treatments and water medications.

  5. Tend to sows that do not feel well and will need more assistance at farrowing, as well as provide treatment to reduce fever, treat secondary bacterial infections and have fresh feed and water available. Assisting sows in farrowing will greatly help sow death loss during a PRRS break, as most sows die because of retained pigs.

  6. Get piglets started right from Day 1 — keep them warm, dry and suckling in the first six hours of life to ensure consumption of colostrum. This is critical in an already immune-compromised animal.

Bruner also emphasizes how PRRS virus affects a sow farm is very strain-dependent. Some strains are devastating reproductively, while others affect the piglets and result in higher levels of preweaning mortality.

If good herd immunity develops, sometimes the herd can go through a natural disease progression without a treatment regimen. Some strains sweep quickly through an operation, while others can take months to infect all breeding animals. Farms with a previous infection can take longer to infect because of previous immunity to PRRS virus.

Air Filtration

The ironic thing about the cost of a PRRS break that Bruner documented is that it is fairly close to what it costs to add an air filtration system to a sow farm, says Darwin Reicks, DVM, of the Swine Vet Center.

Up-front costs vary depending on filter type and building type. But if your operation has a history of breaking with PRRS, installing a filtration system is a “no-brainer,” he says.

“Air filtration is a technology that has a future in advancing biosecurity,” Reicks says. “At first, people thought it was too expensive for sow farms. But we really don't see the difference between boar studs and sow farms.”

In fact, the loss from a PRRS break is substantially higher on a sow farm than a boar stud. “The downstream losses in finishing pigs are where the real losses are and that positive pig flow comes from a sow farm break,” he notes.

“We talk a lot about the impact of variation, but if you market pigs in a three-week period, you have to get them out. If you still have that huge bottom end and need three more weeks to grow pigs, that is tying up a barn, and you are going to lose a lot of money if those slow-growing pigs end up in a cull market or are docked for being lights,” Bruner reports.

Reicks says air filtration can help avoid those PRRS wrecks. He has records on 36 filtered systems — 10 sow farms, two clinic research farms and the rest as boar studs, including the first filtered boar stud (2005), which remains free of PRRS to this day.

“The history on those 36 farms in the five years prior to filtration is that they were breaking with PRRS at a rate of 30% per year. Of the farms with 100% filtration, there has only been one break and that was due to a trucking mishap,” he says. “What that says in my mind is that the majority of the PRRS breaks were by aerosol on these farms.”

There are still a number of farms with partial air filtration that just put filters in above the ceiling inlets for winter ventilation and in summer the air comes in unfiltered through the cool cells. These farms are breaking with PRRS at a rate of about 9% per year vs. a 30% break rate before partial filtration. All of the farms equipped in the past couple of years have been 100% filtered.

“I don't think there is any question that we are reducing the break rate. But there are still other ways the farms can break: no filtration in the summer, trucking issues or other types of biosecurity problems,” Reicks reminds.

If a building has the type of ventilation system that is operated the same all year, the cost is less. But if air enters one way in winter (ceiling inlets) and another way in summer (ceiling inlets closed and tunnel ventilated), more filters are needed because two systems are being filtered. With tunnel ventilation, a filter bank must be built, also adding cost to the project, Reicks says.

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Sow farms must also install a double-door system for loading out weaned pigs, culls and dead animals, etc. to avoid letting in outside air.

Filters vary in cost from the inexpensive MERV 14, which can be used on moderate-risk farms (all of the air comes in through the attic) to the higher-cost MERV 16, (where filter banks are used).

“Over 10 years, including replacing the pre-filters every six months, replacing the main filters every three years, and including all installation costs, plus costs to replace filters, air filtrations costs in the range of $1.20-$2.20/pig. This cost range is mainly driven by which filter you choose, the type of ventilation system you have, and length of life you get out of the main filters,” Reicks says.

“People may look at it and say, ‘I am a high-risk farm, and I've got attic and tunnel ventilation. My cost will probably be closer to $2.20/pig, so I am not going to do it because it is a lot more expensive,’” he adds. “But if you are breaking at twice the rate of the other guy who is able to filter his buildings for a dollar a pig, then you are equal.”

It may seem too expensive, but if you save one PRRS break, you pay for the whole thing, Reicks stresses.

The next horizon is filtering finishing sites. “But right now the cost for filtering finishing is in the $4-5/pig range, so some type of partial filtration system is needed to take on a minimal amount of risk and cut the cost in half,” he says.

Yeske reminds that even with filtration, producers must be vigilant 24/7 to maximize building and herd biosecurity and minimize air leaks.

Eradicating PRRS will take a groundswell of industry support, starting with producers who have the most to gain, according to Yeske.

“I think this is an economic problem that is kind of like the elephant in the room. Everybody is afraid to talk about it because it is so big and there are so many PRRS-positive herds. The guess is an estimated 80% of the herds nationally are positive for PRRS, lower in July and higher in the fall,” he says.

“Everyone is asking how they can become more efficient to lower costs over the long term, yet they are questioning why we are talking about PRRS eradication in one of the worst economic times. The reason is because eradication will make us more competitive, long term,” he observes.