Is fogging an M. hyo-elimination option for your swine herd?

Paul Yeske, DVM, with the Swine Vet Center in St. Peter, Minn., has seen repeatable success with Mycoplasma hyopneumoniae (M. hyo) elimination, along with the downstream effect of lower cost of production, better average daily gain, better feed efficiency and lower mortality. He estimates the benefit of M. hyo elimination to be in the $3 to $4 range per pig, conservatively, with some herds seeing a benefit of as much as $10 per pig when other diseases are eliminated at the same time. Now, the relatively new protocol of fogging a barn may make M. hyo elimination even more attractive.

This technology came out of the frustration of trying to evenly and efficiently expose animals to the bacterium, Yeske told Pig Health Today. Fogging allows for faster exposure to establish “time zero” for elimination, so gilts can be stable by the time they enter the sow herd.

“That reduction of time for M. hyo to spread from animal to animal in a natural way is probably the biggest advantage,” he said. Previously, Yeske would use intratracheal exposure of seeder animals, but said, “It’s a lot of work and you still have slow spread from animal to animal. Fogging has been very successful for us, although it’s still new technology and there are some lessons to learn as we go forward.”

Research needed

Fogging appears to be an effective method for M. hyo elimination, but Yeske said critical questions need to be answered on the technology:

• How long can the inoculums be stored?
• How long can the lungs used for the inoculum be stored if the herd is kept positive?
• What’s the best media to use for exposure?
• Should an M. hyo media be used, or can we use phosphate buffered saline?
• Which products work best for fogging in terms of storage and/or the fogging procedure?
• What’s the right dosage and volume level?

“So far it’s been very good, even with the experimental method we’ve used, but I think there’s an opportunity for it to be better,” Yeske said, adding that, “We just need to support the researchers to do the difficult work to answer these questions.”

Other methods also effective

Yeske said depopulation/repopulation is the “tried and true” method that works every time but it’s also the most expensive. It’s difficult for people to invest the money unless there are other compelling reasons, such as additional disease challenges or parity re-distribution, he noted.

The herd closure model is to keep a herd closed (no new introductions) beyond 240 days, Yeske said. Hee recommends medicating the sow herd and piglets at the end of the closure, which allowed the pigs’ immune systems to help as much as possible. Timing varies, but this model has been the most successful and has had the least amount of impact on production.

“We’ve been in the 75% to 80% success rate over time and it’s been the most repeatable system,” he said. “Generally, mycoplasma elimination has been done in conjunction with other diseases, such as porcine reproductive and respiratory syndrome (PRRS). It just adds a little more time to standard PRRS-closure and you also get rid of the M. hyo,” he said.

Another method involves whole-herd medication, without a herd closure, but Yeske said the success rate is closer to 50% when medication is done without herd closure.

“If we do limited-herd closure (150-240 days) and then medicate at the end, the process has been more successful and closer to the long-term closure success rates,” he said.

Useful tool for control or elimination

Fogging may not be a silver bullet, but Yeske said it’s a useful tool for M. hyo control, “whether you’re doing ongoing control and acclimating replacements into the herd, or you’re looking at elimination. The technology is fairly inexpensive, so it’s about having your herd veterinarian help set up the program to make sure you’re doing everything the right way.”

Yeske is often asked how likely a herd is to stay negative if a producer goes through the Mycoplasma-elimination process, especially in pig-dense areas.

“We did some research two years ago and found that lateral introductions happen, but they are rare,” Yeske said. “We saw 94% of the herds stay negative, even in pig-dense areas.”

He recommended producers and veterinarians work on herd stabilization, with consideration given to elimination if other issues are impacting the herd.