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Vaccination Lapses Lead To PRV Outbreaks

When producers quit vaccinating for PRV, their herds suffered the consequences - infection and quarantine. Iowa has been hit especially hard.

Just as the pork industry was zeroing in on pseudorabies (PRV) eradication, a number of outbreaks threw the effort off target.

State veterinarians met recently to approve plans for surveillance after eradication.

But most talk at their meeting centered on the impact of the big PRV breaks in Iowa and new cases in Minnesota, Nebraska and Illinois.

Many industry leaders remain convinced the 10-year eradication campaign will finish on time - at the end of 2000.

Iowa's Big Breaks Iowa's PRV program had been running smoothly. It had less than 200 quarantined herds, recalls John Schiltz, state veterinarian.

Then cases started to pop up in December 1999 and January 2000. By April 1, the number of quarantines doubled to 408. He expects that number to grow this spring and then decline over the next few months. The map on page 46 plots PRV cases in Iowa.

Newly infected herds have been profiled, including seedstock, feeder pig and farrow-to-finish operations but mainly finishing operations.

Some producers quit vaccinating finishers for PRV to lower production costs because hog prices have been depressed, observes Lawrence Birchmeier, DVM, coordinator of PRV programs for the Iowa Department of Agriculture. Hog density, a cool, damp winter and a large population of naive finishers triggered an explosive aerosol area spread of the virus.

Responding rapidly to the crisis, the industry and the Iowa Department of Agriculture developed an action plan. Iowa Governor Tom Vilsack has signed the plan released by Secretary of Agriculture Patty Judge. It calls for:

* Mandatory vaccination of all pigs in the northern 66 Stage 2 (control) counties with a modified-live-virus vaccine. The breeding herd is to be vaccinated quarterly and farrow-to-finish pigs at least once. Qualified negative breeding herds are exempt. Owners are solely liable for providing and administering the vaccine. No funds have been authorized for vaccination, says Schiltz.

But the Iowa governor has appealed to the federal government to help small producers with the cost of compliance, fearing that without it they will be forced out of business.

* Test and removal becomes effective Aug. 1. All infected breeding herds must conduct whole-herd testing within 15 days of infection; all positive hogs must move by sealed truck directly to slaughter. All infected feeder pigs or cull hogs must move directly to slaughter or to an approved premise for feeding.

* Approved premises have to be 11/2 miles from a negative herd and 3 miles from a qualified negative herd. They can't be sited in Iowa's 33 Stage 3 (cleanup) counties or PRV-free counties.

* Only non-infected herds can enter Iowa, except directly to slaughter.

* Civil penalties of at least $100 but not more than $1,000 can be imposed for violations. Falsification of a certificate of inspection is a civil penalty of $5,000/hog, up to $25,000. Failure to vaccinate is a civil penalty of $2/hog.

Vaccine Pressure Washington, IA, producer Jim Ledger warns producers against trying to skirt the tightened rules. "They might think they are going to be able to get by without vaccinating. But my suggestion to them would be to check their liability insurance very close. There may be a clause in there for neglect."

Iowa State University's diagnostic lab will expand surveillance monitoring of PRV vaccination practices, says Schiltz.

At Iowa Select Farms in north central Iowa, vaccination of breeding stock and finishers will continue until it is felt Iowa is PRV-free, says company veterinarian Howard Hill.

Finishers are vaccinated a minimum of two doses and sows four times a year. "If everybody gets behind this program, we'll get it whipped," stresses Hill.

Profiling The Breaks Most problems were in finishers; the dozen or so sites that tested positive for PRV have had few clinical signs, says Hill. Three quarantined sow sites are left.

Disease breaks are not unusual at the end of an eradication program, observes Hill. Cleanup is painful. But everyone blanket vaccinating their herds is the most efficient way to eradicate PRV in the long run.

PRV cleanup has not been very painful for Dennis Friest of Radcliffe, IA. PRV went through his herd last December, but it only affected the finishers, and there were no losses. Sows are being vaccinated prior to farrowing.

After PRV was diagnosed, he went through and vaccinated all grow-finish hogs one time.

For Friest, porcine reproductive and respiratory syndrome (PRRS), coupled with a bout of Actinobacillus pleuropneumonia, were much more destructive than PRV. However, the cause is the same for all these diseases - dense hog concentration, typical throughout north central Iowa, he says.

Friest, a 250-sow, farrow-to-finish pork producer, thinks it's unrealistic to think Iowa can finish PRV eradication this year.

Jim Lewis, a 3,200-sow producer at Welcome, MN, says without drastic action, there will be bumps in the road.

"We need to learn from North Carolina's experience. They tried some different programs to get PRV eradicated. But until they did mass vaccination in the high-density areas, they didn't get it done," says Lewis.

He believes complacency is as much a reason as low hog prices for not vaccinating. "I know a year ago we weren't vaccinating our finishers because incidence had dropped to such a low level," he admits. "There was some PRV in Martin County (MN), but we never had vaccinated anything but the sows, and that seemed to be enough."

But his luck ran out a year ago. One finishing barn broke with PRV. He cleaned up and has vaccinated all finishing hogs ever since.

Recently in Minnesota, several herds in hog-dense Martin County broke with PRV. Two dozen new cases sprung up east of there in Waseca County, the first cases in more than five years.

Lewis declares, "Unless we do something fairly drastic, I'm afraid every winter we are going to have these flare-ups again, and we are going to continue to fight the battle with PRV."

A PRV quarantine can spell death to a three-site pork operation in Minnesota, he notes. The quarantine prohibits movement off a site, except to slaughter.

States around Iowa have added to tough rules to stop pseudorabies (PRV) at the border. New cases of PRV and rules include:

Illinois: Four new PRV cases have been diagnosed. The state had been clean. State veterinarian Dick Hull says investigators feel some or all of the cases came from Iowa.

Breeders or feeders from Iowa must now test negative 30 days prior to entry, reports Hull. All Iowa slaughter hogs from quarantined herds must travel with a special permit in a sealed truck.

Illinois is considering additional restrictions. One proposal is to require imported feeder pigs from Stage 1 or 2 states to be quarantined until they can be retested at 21-60 days. Those same pigs would be tested 15 days before importation.

Nebraska: Three new quarantines were imposed just as the last one was about to be lifted, says PRV epidemiologist Jim Weiss, DVM. Two were unauthorized importations of infected breeding stock and feeder pigs. One infection came from Iowa, a second from Minnesota. The third case involved a Nebraska hog broker who sold female market hogs as replacement gilts.

New restrictions on Stage 2 Iowa counties were imposed in March. Breeding stock and boar semen must come from qualified negative herds that are tested monthly.

Existing rules also require breeding stock from Stage 2 counties to be quarantined until re-test on arrival. Feeder pigs from Stage 2 counties must come from herds tested within the last 30 days. Pigs more than 13 weeks of age must be vaccinated; segregated early weaned pigs must come from a vaccinated herd. All feeder pigs are quarantined to slaughter. Iowa hogs for slaughter in Nebraska move on special permit.

Minnesota: The state has about three dozen new PRV-infected sites. About 40 sites are quarantined. Circle testing has not shown any cases that can be traced to Iowa herds, says Paul Anderson, DVM, PRV program coordinator for the state Board of Animal Health.

Regulations were changed in December 1999. Imported feeder pigs from Stage 2 counties must test negative for PRV within 30 days of shipment and come from a PRV-negative premise. They are restricted to a quarantined premise until being shipped to slaughter.

Existing rules require breeding stock to enter on a 30-day test and be re-tested in 30 days. Slaughter hogs come in sealed trucks under special permit.

South Dakota: The state is free of PRV and placed tough restrictions on Iowa imports last summer, says state veterinarian Sam Holland. Stage 3 (lower 33 counties of Iowa in the PRV cleanup phase) status is no longer recognized.

Also, a 30-day test of the farm of origin is required for all imported breeders and feeders.

In counties with more than a 1% infection rate, entry is restricted to only those with a special permit and after a risk assessment of shipments.

As of December, slaughter hogs can enter only on special permit in sealed trucks. Those hogs must be unloaded at separate facilities at the packing plant.

Holland admits the tough rules really have cut down Iowa imports. "We have had to do it to protect our industry, and I think it has worked pretty well," he says.