Follow these 10 points and you greatly improve the odds of beating Porcine Reproductive and Respiratory Syndrome (PRRS).
So says Max Rodibaugh, DVM, Swine Health Services. A few producers in his hog-dense practice near Frankfort, IN, have hit the jackpot. They have been able to steer clear of PRRS entirely for several years. They don't use vaccine and they carefully check all introductions to be sure the seedstock they are bringing in tests negative, he says.
The Top Ten List By far, says Rodibaugh, the first two points on the list, isolation and acclimation, are the main keys to successful PRRS control.
1. Isolation: Establish a period of time (usually 30 days) and place to isolate incoming stock that could be incubating potential problems from the rest of the herd. This serves as protection from PRRS. But it should also be the rule for any potential disease incubating in a source herd - whether it be purchased or your own internal replacements.
Explains Rodibaugh: "I think sometimes that is where people cheat. They say, 'Well, we raised them. They are immune to our bugs. Let's just take them back into the breeding herd.'"
Fact is, those internal replacements could have come from segregated production and be healthier than the average sow in the herd. The sow herd may be carrying a low level of immunity. But the addition of those naive gilts may react to the disease, producing an infection in the herd.
If you vaccinate for PRRS, do it early in the isolation period. That's partly because if you have a negative animal, it will shed vaccine virus for quite some time (with modified live virus vaccine) and it could expose contact animals.
2. Acclimation: Develop a plan with your herd veterinarian, as you may want to start acclimation before 30 days isolation is up. That's particularly true for PRRS, because it gives that animal more time to recover and quit shedding the virus, explains Rodibaugh.
Acclimation means exposing incoming animals to the herd of destination. Length of acclimation depends on the confidence you have in your source herd and your herd status for PRRS, he says. It's known that naive pigs can be viremic (presence of virus in the blood indicating infection) for 6-8 weeks, and new data shows it may be even longer, he points out.
Causing an even bigger stir these days is what to expose new stock to. Rodibaugh suggests exposure to fecal material from sows in farrowing at least weekly during acclimation. Don't use stillbirths. Cull sows are good, but younger parity sows are better because they are more likely to be shedding disease organisms. In some cases, nursery pigs may be used for exposure.
If you're going to test those incoming animals, it should be done at least twice during acclimation to find out if they appear to be actively infected with PRRS, he says.
An emerging trend in gilt introduction is Isowean age pigs. (10-19 days old) "I think we have to be careful we don't get caught thinking we can bring them in and put them into our nursery. To me, we still have to isolate and acclimate those pigs," stresses Rodibaugh. Introducing Isowean gilts straight into a nursery could actually be worse than introducing adult females into the breeding herd when it comes to PRRS. That's because pigs around weaning age are often the most actively infected, says Rodibaugh.
But there are also big advantages to Isowean introductions. Those young pigs have more time to become acclimated to pathogens on the farm. And they don't need a huge isolation/acclimation (I/A) facility.
3. Know the immune status of your herd. "I'm surprised at the number of herds that still don't know what's going on in their herds. They say, 'well, we've never seen any problems, so we must be negative.' And I'll bet they probably are not right," comments Rodibaugh.
Find out what's going on, he urges. Have your veterinarian conduct a serological survey consisting of 20-30 sows, 10-15 nursery pigs and 10-20 finishers. Realize it will be a little tougher to interpret serology results if you are vaccinating for PRRS because vaccinated pigs test positive for the disease.
Herds should be monitored every six to 12 months, especially if a sow herd and/or finishers are left unvaccinated.
4. Know the status of your seedstock supplier. Are there clinical signs in the herd and, if so, what's going on? What is the vaccination protocol? If animals are going positive for PRRS, find out at what stage of production. How often do they send replacements?
Key question to ask yourself: Can you rely on your source herd to notify you if there is a change in the PRRS status of their herd?
Check on the level of management. For instance, is the operation continuous flow or all-in, all-out? That can tell you a lot about attention to detail and concern about animal health, says Rodibaugh.
5. Know the PRRS status of your semen source. Find out how boars are handled going into a stud, whether they are tested before entry and the I/A protocol. Don't consider using semen from a stud that doesn't isolate boars before entry into the stud.
What criteria is the stud using to say that it is negative for PRRS? "Some studs may be indicating they are negative, but they may not be truly seronegative," he says. Rodibaugh explains that even though boars may currently test negative, they may have tested positive in the past, and could still be harboring the virus in their bodies.
6. Do the diagnostics. Early diagnosis can be critical in minimizing the effects of PRRS. It may take several samples to find the virus, but it's worth it to take steps early so you can take some action and anticipate what might happen down the road.
Of course, you want to do serum and tissue tests on breeding stock. But don't forget to analyze what's going on in grow-finish and the nursery where a chronic infection could be brewing.
7. Vaccinate or not? "Vaccine is not the total answer but it is not the total problem, either," observes Rodibaugh. Vaccine virus does replicate in naive or negative pigs. The vaccine virus was found up to 34 days in a group of pigs vaccinated at weaning, according to a relatively new study.
Some work has been done in an attempt to eliminate the PRRS virus using vaccine plus pig flow changes. He doubts that virus could be eliminated by vaccine alone.
One thing for sure, Rodibaugh opposes vaccinating pregnant sows (using a modified live virus vaccine) except for special cases such as a severe outbreak. He vaccinates sows a week or two after farrowing.
Replacement animals should be vaccinated early in the isolation period to afford time for vaccine virus to run its course.
8. Make decisions based on objective, factual information. Research the subject and talk to a trusted observer before launching a control program. Remember, there isn't a standard recipe that is always going to work, he stresses.
9. Study pig flow. Limit crossfostering to the first 24 hours of life and only within the same farrowing room. Don't backfoster. Euthanize sick pigs. Practice strict AIAO in the nursery.
Overall, the more you can do to reduce age variation within a room and within a site, the better job you'll do of minimizing the effects of PRRS.
10. Practice biosecurity. Watch out for any vehicles coming onto your farm that may be a source of infection - feed trucks, cull trucks, trucks hauling market hogs. Poor traffic flow can ruin your isolation program.
Most of all, do the best you can to get incoming stock acclimated to your farm. Don't let naive animals enter an infected sow herd or you could end up with persistently infected pigs.
