Strategies to weaken PRRS’ grip on US herds

After more than three decades, porcine reproductive and respiratory syndrome (PRRS) remains a serious disease threat to swine units in the US.

“It’s the one disease that makes me look bad,” reported Brian Bishop, DVM, Veterinary Medical Center, Worthington, Minnesota. “As an industry, we still don’t know everything about it after 30-plus years.”

What they do know includes several strategies to reduce the risk of PRRS outbreaks. But follow-through on these strategies can be tough.

The people factor

Vaccines can help reduce the threat of PRRS when the products are administered correctly. But equally important is making sure the unit staff is aware of potential PRRS-infected litters in the farrowing room.

“If they start moving those piglets around to other litters, of course they’ve spread PRRS around,” Bishop said.

“A lot of our ‘PRRS failures’ aren’t really the vaccine’s fault at all…or how people are administering vaccine,” he continued. “It comes down to the daily process that people go through on a day-to-day basis on the sow farm. And, of course, is the vaccine even being given?”

Staff must be closely communicated with regarding health status of the herd and procedures to prevent disease spread.

‘Tails and testicles’ testing

Regular testing of processing fluids, tails and testicles can help a sow unit stay on top of PRRS.

“[Our] general practice on a sow herd that has not yet broke [with PRRS] has been to test these processing fluids on a monthly basis,” Bishop said. “We’re finding PRRS in those processing fluids sometimes a couple weeks before we see anything on the sow farm.”

Sharing the results with employees helps them understand how easily PRRS can spread through an entire herd.

“I did the calculation for a client…and found just one piglet had enough PRRS…to infect the entire sow population,” Bishop explained. “I say, ‘This is why we have to be careful with these piglets because we only have 1,500 sows on the farm, and there’s enough [PRRS] in that piglet to infect 6 million.’”

Vaccine use

Some hog units vaccinate the entire herd to eliminate PRRS, according to Bishop.

“It used to be a live-virus inoculate…intentionally exposing sows to a live serum,” he explained. “What we’re finding is that [a live serum] is a lot harder on sows and piglets than we think…Sows are going to get sick and we see a lot of production constraints from that.”

For his clients, Bishop recommends vaccinating the herd around Oct. 15 and March 15, which are typical times when sow herds in their area break with PRRS. But there are variations in these break times.

To stay aware of PRRS and other disease problems in their area, Bishop and other veterinarians at the clinic participate in the Morrison Swine Health Monitoring Program. Weekly, they report any change in PRRS status on client farms.

The information is anonymous and included in the program’s weekly disease reports sent out to all clinics participating. Bishop can check to see if there are other PRRS and disease outbreaks in any area that may affect their clients.

More biosecurity in finishing

A reduction in PRRS outbreaks will require more biosecurity in finishing units, Bishop contended.

“A client where we test routinely for PRRS uses shower-in/shower-out on sow farms and has had no PRRS breaks for 3 years,” he related. “Only two nursery groups out of 36 broke with PRRS. But in the finisher, 100% broke with PRRS.”

None of the finishers had shower-in/shower-out facilities, just a bench to change into coveralls and boots for biosecurity.

“That’s a tremendous cost to have every single [finisher] group break; to build a shower is pretty cheap,” Bishop explained. “A number of [finishers] are going that way. But there’s definitely a need for better awareness of finisher biosecurity.”

Future technology

If PRRS continues to remain so resilient, it may take something in the future to end its reign.

“There is some technology coming out with pigs that cannot be infected by PRRS,” Bishop said. “That’s still off in the future and once those hit the market, PRRS won’t be an issue.

“But there’s always going to be a new disease that will be a problem,” he added. “There’s always something new.”