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North Carolina--Completion of PRV Cleanup Campaign Near

In 1997, the state/federal pseudorabies (PRV) eradication program was gaining momentum. But industry officials were getting worried about the lack of progress in one state - North Carolina.The No. 2 hog state was saddled with 600-plus quarantined herds. There didn't seem to be any signs of progress.Then an event occurred that changed everything. A national PRV Summit was held in Kenansville. Industry

In 1997, the state/federal pseudorabies (PRV) eradication program was gaining momentum. But industry officials were getting worried about the lack of progress in one state - North Carolina.

The No. 2 hog state was saddled with 600-plus quarantined herds. There didn't seem to be any signs of progress.

Then an event occurred that changed everything. A national PRV Summit was held in Kenansville. Industry leaders got a clear commitment from the North Carolina pork industry that they would close ranks and forge ahead with an eradication plan.

North Carolina made amazing strides in a single year, from January 1998 to January 1999, progressing from 449 quarantined hog farms to just 61 (see Table 1).

New state veterinarian M.A. Mixson reports, by mid-February, there has been another leap forward. There are only 40 PRV quarantines left: three sow herds (one has been depopulated and is sitting empty, awaiting final release from quarantine), seven nurseries and the rest are finishing floors (including one farm that has been depopulated and is awaiting quarantine release).

According to Mixson, in January the state applied for all counties in North Carolina to be placed into stage 3 in the five-stage eradication program. To qualify, there must be less than 1% of the total herds infected with PRV, he explains.

"We plan to wait until all herds are off quarantine before we apply for stage 3-4, split-state status," he explains. Herds in stage 4 must have gone a year or more without a PRV infection. The stage 4 application would include all counties, except three - Cumberland, Sampson and Duplin.

Stage 5 is validation of freedom from PRV. Mixson predicts all herds in North Carolina will be off quarantine by the end of May, possibly sooner. The state is shooting to be qualified free (Stage 5) of PRV before the end of 2000, within the eradication program's deadline.

Murphy's Beats Own Goal At Murphy Family Farms, based in Rose Hill, NC, the goal was to complete PRV cleanup by Jan. 1, 1999, says Howard Hill, DVM, director of Veterinary Services. The last quarantines were released in mid-December, two weeks ahead of the goal, ending a four-year struggle that involved cleaning up 35 quarantined hog farms.

Getting the job done took teamwork amongst Murphy Farms' staff working beside state and federal employees. They set goals to be the first of the large hog production companies, that co-exist in hog-dense Duplin and Sampson counties, to have all their farm sites off quarantine. They succeeded.

Cleaning up Murphy's largest sow herds was the biggest challenge to eradication. "I think the main thing that is important in eliminating the disease from specifically our three, 4,400-sow herds was to have a good recordkeeping system and maintain exact animal records," points out Hill.

Because of the size of those sow herds, their newer genetics and high-health status, test and removal was chosen over depopulation as the most economical cleanup choice, he says. "When you start test and removal, you can't rely on poor records. Because as you get further into the program, if an animal comes up positive, and it has been misidentified, you don't know whether you've got active infection or it's a sow you've missed," observes Hill.

"At Murphy's, we compiled all our PRV records into a computerized database, so we knew exactly when an animal had been previously tested. And every time we did a test on an animal, we would go back to verify its previous status," says Hill.

An automated recordkeeping system was critical with from 3,600 to 4,400 sows, as some herds had infection rates up to 60-70%, explains Terry Tate, production manager for four of Murphy's Warsaw, NC, farm sites. That includes two, 4,400-sow farms, both heavily infected with PRV, and two, 3,600-sow farms, one that was infected and the other that was never infected.

Declares Tate, "You are trying to track each individual sow, so it is imperative that you know where she is at and when." So when test results come back, you need to identify which of those animals are positive.

Tate and his farm staff came up with three checks and balances to be absolutely sure every time a test result came back positive, that the positive sow was identified, placed on a cull truck and left the farm:

First, the farm's computerized PigChamp records were used to accurately identify those positive sows;

Second, those sows were flagged in the records; and

Third, the actual test chart was taken out to that sow group. The card of every positive sow was marked and she was painted across the back. "We were basically painting the sow orange to make sure she was absolutely identified," notes Tate. "That may seem extreme, but with a population of sows this big, sows can get lost in the shuffle pretty easily."

Early on, a PRV-positive sow would occasionally still slip through the system, usually because an eartag was missing, explains Tate. Without identification, you have no choice but to cull that animal, if you expect to have 100% confidence in your cleanup program.

To keep sows from slipping through, Tate soon figured out that even before the checks and balances could be followed, there was one more step to accuracy in recordkeeping. That was auditing the entire sow herd inventory to make sure that all sows had their eartags and that none of the tags had been misread.

With those identification steps in place, cleanup began in earnest. Test bleedings were scheduled for sow groups. The whole herd was being bled, two groups at a time, every other week to spread the testing out, Tate explains. That eased the workload and allowed production at the continuous-flow sow farms to function without interfering with cleanup.

At the Rose Hill farms, sows produce 12-lb. pigs, weaning at 16-17 days of age. Those pigs are trucked to a Murphy nursery site. At 45 lb., they are moved to a company finishing site.

PRV Vaccination Surprisingly, despite the heavy levels of infection, Tate and staff saw few signs that PRV was even present on the sow farms.

That may have been due, in part, to the intensive PRV vaccination protocol implemented by Murphy veterinary staff. The program for internal multiplication replacement stock included: day one intranasal vaccine, vaccination at 8, 13, 22 and 26 weeks of age. "They were getting five (PRV) vaccinations before they entered the breeding herd," says Tate. Any new arrival to a farm, gilt or boar, would be multiple vaccinated as well. After they entered the breeding herd, gilts/sows would also be vaccinated for PRV pre-farrowing; boars were vaccinated four times/year.

Once the pigs left the sow farms, they relied on maternal immunity for protection through the nursery phase, according to Hill. Feeder pigs were vaccinated for PRV on arrival at the finishing site.

The Warsaw, NC, operation is a closed system, meaning that the four sow farms Tate oversees provide weaned pigs all to the same set of nurseries, feeder pigs all to the same set of finishers. All are located on one, 4,000-acre tract of land in the area.

Surveillance Program Though Murphy's farms have all been released from quarantine for PRV, every precaution is being taken to ensure the disease does not make a comeback.

Finishing hogs are still being vaccinated in the two hog-dense counties of Duplin and Sampson on arrival. The breeding herd has returned to a normal schedule of protective vaccination, says Hill.

He points out that they are doing more testing in their current surveillance program than they did during the cleanup program. Hill observes, "My feeling is that on the front end of your surveillance program, you need to do more testing so that new infections can be identified quickly and immediate action can be taken. We will test more herds, more often in 1999, than we did in previous years."

In Murphy's stage 2 (PRV control stage) farms, a representative sample of sows on all sow farms are tested quarterly. A representative sample of sows on all Stage 3 farms are tested annually. Boar studs and multiplication farms are tested monthly. Murphy's is also testing 10% of finishers every four months in units in the more intensive hog counties of Duplin, Sampson and Lenoir.

Declares Hill, "Yes, it will be a lot of testing. But we have already spent millions and millions of dollars eradicating this disease. And we feel by spending money on a surveillance program, we gain confidence that we don't have any PRV. In the end, it will allow us to cut back on vaccine quicker and we will actually save considerable amount of money on vaccine down the road.

"It will also give people in other states confidence that North Carolina is, in fact, free of PRV. And hopefully, as the U.S. becomes free, it will translate into new marketsfor us internationally."

Trading PRV For PRRS According to Hill, PRV cleanup has produced one down side for Murphy's and some other large hog farms in North Carolina. To clean up PRV in two large sow farms, Murphy's produced replacement gilts in an off-site breeding project. The high turnover rate (30-40% and more) of some PRV-infected sow groups and subsequent higher replacement rates destabilized some of their sow farms, resulting in PRRS (Porcine Reproductive and Respiratory Syndrome) breaks. "When we had to add large numbers of replacements, adding bred gilts and mature gilts, we caused some PRRS outbreaks," says Hill.

"It just shows you that the introduction of mature gilts into a herd is not the safest way to go as far as herd stabilization regarding PRRS. Upgrading genetics is important, but maintaining herd health is even more important, because you can't sell a dead pig," he points out.

In an effort to maintain PRRS-positive herds in a stable state, Hill says Murphy Family Farms is moving to 100% artificial insemination (A.I.) and is introducing all new animals as weaned pigs to allow for on-farm acclimation and development prior to being introduced into the breeding herd.

Security is tight at Murphy's sow farms to keep out people and pigs. The driveway entrance to each premise is locked at night, as are all of the buildings. Sites feature perimeter fencing topped by barbed wire, says Tate. Facilities are shower-in (mandatory), shower-out (voluntary). The double-curtain-sided buildings are connected by enclosed walkways. Both curtains and walkways are bird-proofed.

"We want to try to limit entries into these farms and make absolutely sure that all of the employees here recognize the importance of a sound biosecurity program," remarks Tate.

North Carolina pork producers were spending a million dollars a month when the state accelerated pseudorabies (PRV) cleanup program started in 1997, recalls John Atwell, recently-retired state veterinarian.

Assistant State Veterinarian Tom McGinn adds producers finally realized that if they didn't improve their efforts and clean up their herds, their lucrative pig export business to the Midwest might be lost. North Carolina producers exported 2.7 million feeder pigs in 1998. Close to 35,000 breeding stock were also shipped out of state.

They also realized that PRV reinfections could swiftly overwhelm their herds, placing them back at square one, maybe even costing them their farms, notes McGinn.

A third hammer was added in mid-1998 when North Carolina quickly put into place federal requirements for test and removal of PRV-positive breeding stock.

For their part, North Carolina pork producers should be given a lot of credit, says McGinn. When the issue got serious, they dug in, pulled together and moved ahead to clean up. They have paid for all of their own vaccine. They have helped neighbors coordinate cleanup and provided replacement breeding stock to small operators at market price.

The state supplied needles and syringes free of charge and have been working five days a week assisting producers with blood testing. There have been lots of busted knuckles, busted hands and sweat expended in testing and cleaning up herds, he stresses.

The state tested just short of half a million blood samples for PRV in 1998, says McGinn.

As the eradication program winds down, McGinn says the state is taking additional surveillance steps. Testing in state slaughter plants was to start in March. Random testing of herds in the stage 2 area will doubled to four times a year. Stage 3 herds will be re-bled during the first six months of this year, he says.

"Essentially, we are more than doubling our efforts," explains McGinn. "We recognize if there are more infected herds out there, we don't want to find them by accident."