The U.S. is inching ever closer to meeting its goal of eradicating pseudorabies. The next few months will determine the campaign's future.
The stage is set to complete the pseudorabies (PRV) eradication program. At 112 herds, the U.S. pork industry is at its lowest count for quarantined, infected herds since the eradication program was launched in 1989.
However, these next two months of winter are PRV crunch time, says John Schiltz, DVM. The Iowa state veterinarian says the past two winters are a grim reminder of what can happen to throw a wrench into momentum.
During the winter of 1999, Minnesota experienced the worst jump in cases in three years, prompting a number of owners to opt for the federal PRV buy-out plan. In the winter of 2000, vaccination lapses led to four major outbreaks in Iowa. Two dozen new cases were recorded in southeast Minnesota last year.
States with Quarantined Herds
Iowa has 106 PRV-quarantined operations. By mid-February, Minnesota and Nebraska had both recorded two new infections, and Indiana had a small herd test positive for the disease.
Both Minnesota cases are in Martin County. The first involves an 800-sow operation where only 21 sows were tested positive. Paul Anderson, DVM, Minnesota Board of Animal Health, expects the herd to test clean in 30 days. A 2,500-sow Nebraska herd in Colfax County broke with clinical signs of PRV in mid-January. Pigs from that herd were sold to a second Martin County operation. Anderson reports that 25 of 30 pigs from this Martin County, MN, operation tested positive for PRV on Feb. 5.
The Nebraska herd was located a mile from a finisher operation that also was infected recently with PRV, says Jim Weiss, DVM, epidemiologist for the Nebraska Department of Agriculture. Both operations have depopulated but will remain quarantined from 30 to 90 days, he says.
A Howard County, IN, herd that was a local supplier of show hogs was quarantined after two sows tested positive for PRV. The small, five-sow herd will be depopulated soon, according to the Indiana Board of Animal Health.
One garbage feeding herd in New jersey remains infected.
This past January, Iowa recorded 34 new PRV infections, while releasing 87 sites from infected status, says Schiltz. The numbers are steadily declining.
Declares Schiltz: “We've made big strides to get our numbers down. The level of testing that we are doing is significant. The fact that we are holding our own in detecting a low number of infected herds has to be viewed as a positive, considering how far back we slid last year.”
If Iowa gets through winter without any major outbreaks, the state likely will eradicate PRV by mid-summer, Schiltz projects.
To confirm the infection rate, federal funds have been allocated to conduct surveillance down-the-road testing of all breeding herds, farrow-to-finish and finisher operations in the 66 counties in stage 2 (control) of the eradication program.
Plotting Positive Operations
With the numbers getting down to a manageable level, Iowa Department of Agriculture officials are plotting PRV-positive herds on a map by county. That way they can quickly spot trends.
That plotting resulted in Iowa officials noticing a disturbing trend. A rash of new infections was in Hamilton and Hardin counties, a very dense hog finishing area, explains Schiltz.
At a meeting, the owners agreed to take some stiff new steps beyond state code to control infection. That included double vaccinating finishers (the state code calls for one dose of vaccine) and revaccinating all pigs that are not within three weeks of slaughter in a three-mile radius of any new infections. New state code approved last year also calls for testing a representative sample of swine on each site in stage 2 areas every six months. Owners in the two counties extended that to include testing a representative sample of every group of pigs 30 days before load-out.
“I believe that we have turned the corner on sentiment towards eradication in Iowa, and that's what happens when 99.5% of your herds are clean,” remarks Schiltz.
A few haven't embraced that sentiment, however. Iowa has imposed more than $18,000 in civil penalties since July. Violations include importing out-of-state feeder pigs without performing required testing and vaccination, failing to maintain proper vaccination and test status and illegal movement of pigs.
Schiltz adds that, as of Feb. 1, warning letters for violations became a thing of the past. Producers have been made fully aware of PRV regulations and must now comply with them.
New Technology May Aid PRV Eradication Effort
Meat juice” technology long used in the national salmonella control program in Denmark is being tested for use with the pseudorabies (PRV) eradication campaign in Iowa.
It would be the first formal application of the technology in the U.S., says James D. McKean, DVM. The technology holds promise as an added means of PRV surveillance at slaughter and could speed eradication, says the Iowa State University (ISU) Extension veterinarian.
Slaughter plant sampling has focused on taking serum samples of cull breeding stock, adds Lowell Anderson, DVM, area epidemiologist with USDA's Veterinary Services. The growth of multi-site hog production systems has expanded the number of separate finishing sites and with it increased PRV infections in market hogs.
Testing serum samples using enzyme-linked immunosorbent assay (ELISA) is a suitable procedure for screening cull breeding stock at slaughter. But individual identification is difficult to maintain because ear tags are lost as carcasses are processed, points out McKean.
McKean also notes serum testing doesn't work for market hogs because kill line speeds make it dangerous and difficult to perform.
“So right now there is no program to test slaughter hogs for PRV at market hog packing plants,” says Anderson.
With meat juice technology, normal fluids contained in muscle samples can be collected and tested for PRV after animals are slaughtered. Slap tattoos unreadable during slaughter are visible after dehairing, explains Anderson. This method could be valuable for detection of infection in finishing hogs and trace back to the farm of origin, he says.
ISU researchers collected and compared 196 serum and muscle samples from four units during Accelerated Pseudorabies Eradication Program depopulation. It was an additional, pork checkoff-funded food safety project with the National Pork Producers Council and the National Pork Board. The serum and meat juice test results agreed in 190 of 196 samples taken, reports McKean.
That has led to submission of a proposal to USDA to conduct further testing of the meat juice technology at select Iowa market hog packing plants, he notes.
If results are positive from that pilot project, McKean foresees the meat juice technology being used extensively in PRV surveillance and to help clean up remaining pockets of infection.
With its broad application to diseases like PRV and salmonella, it could very likely get use in many other livestock disease control efforts, suggests McKean, project coordinator.
“It has tremendous benefits for surveillance in possibly replacing down-the-road serum testing for PRV, for foreign animal disease and for establishing certification programs,” adds John Schiltz, state veterinarian.