In my home state of Illinois and many other states, PRV has been eradicated. The program's success has been accelerated the last 18 months by poor hog prices and a government indemnity program buying out many infected herds.
Revisiting PRV Control To keep PRV out of your herd, we need to revisit the disease itself and the ways it can move from hog farm to hog farm.
Many animals such as cattle, sheep, dogs and cats are dead-end hosts. If they become infected, they always die, shortening the time they can spread the disease. Objects like boots, vehicles and clothing also can spread PRV.
We all know of cases where the mechanism of viral spread from one farm to another has not been determined. Some think aerosol transfer happens regularly.
The fact is, pig-to-pig contact is by far the most common means of PRV disease transfer.
Feral (wild) pigs present an added challenge for some states. Chain-link fencing and other special biosecurity techniques may be needed.
Specific ways to keep out PRV include:
1. Know the PRV status of your area and state. If you run a multi-site production system, know the prevalence of the disease at each site in state or out of state. Consult your veterinarian on managing sites for biosecurity, use of vaccine in heavily infected areas and movement from site to site.
2. Remember, if PRV is in your area, dogs, cats and wild scavengers are likely infected, mechanical carriers of the disease.
3. Maintain biosecurity with an off-site isolation area for introducing new breeding stock. We all know this, but some fail to believe it's important. Porcine reproductive and respiratory syndrome (PRRS) has made believers of most of us. Biosecurity is equally important in keeping PRV out of the farm.
Your state may require a blood test of breeding stock for PRV. This involves blood testing all or part of each group of pigs that go through your isolation facility on their way to the main farm. The time frame will be explained by the state's Department of Agriculture or your veterinarian.
Blood samples drawn for PRV are very useful to test for other diseases potentially in new breeding stock as part of an overall herd health program.
4. Consult your veterinarian for special help with a feral (wild) pig problem.
5. Don't bring show pigs back to the farm. This goes for other infectious diseases, too.
6. Keep in mind the huge trend to ship large groups of pigs interstate to be fed by contract finishers.
In summary, except for endemic (heavily infected) areas, the largest problems now in keeping PRV out of your farm are introduction of infected pigs, feral pigs and the unauthorized movement of untested pigs.
If the control system breaks down, a potential explosion of PRV could happen in a large population of susceptible pigs. Continuous monitoring in one form or another cuts the risk in all of these cases.
Case Study Several years ago, we received a frantic call from a client. He owned a single site, 700-sow, farrow-to-finish operation. A breeding stock company had just told him the boars he received 2-3 weeks earlier may be infected with PRV.
One of the boar production farms had broken with PRV. Boars from this farm and other boar production farms were on this delivery. Several deliveries were made at other farms before they reached our client's farm.
Fortunately, the boars were placed in a separate barn that was on-site, off-site. A change of clothes and a boot wash were standard procedure in and out of the isolation facility. We blood tested all of the new boars and some gilts that were in the building for a breeding trial. All of the blood samples came back positive. All pigs in the barn were marketed. The biosecurity plan was revisited and emphasized.
We tested the sow herd and grow/finish groups for several months without detecting PRV. We were very lucky in this case. The isolation biosecurity plan had done its job.
Thanks to the quick response of the breeding stock company and the faithful implementation of the biosecurity plan by the staff, an economic disaster was avoided.
Conclusion Keeping PRV out of your herd should be part of a good isolation strategy and biosecurity plan that you and your veterinarian tailor to your particular production scheme. The basic rules are the same for all, but many variations and special circumstances require attention by your veterinarian. Use him or her aggressively in building and monitoring a good biosecurity plan for PRV and other diseases.