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Stomping out Mycoplasma hyopneumoniae for good

SVC veterinarian says it comes down to right test, right time and right number of samples.

Laura Bruner will admit she has disdain for Mycoplasma hyopneumoniae, more so than for porcine reproductive and respiratory syndrome virus. That's because it can go undetected for a long period of time — especially if you have a stable herd, or you believe it to be stable.

Once you figure out that your herd is unstable, Bruner says it feels like it takes forever to get that herd back to square one.

"It kills late-finishing pigs, so you have all your time and money and energy invested into these animals, and then they tend to die in late finishing at 200 to 300 pounds; and you have a producer looking at you saying, 'Doc, are you going to help me? My pigs are dying,'" Bruner says.

The veterinarian with Swine Vet Center, based in St. Peter, Minn., believes mycoplasma is one of the most significant pathogens to affect pigs today, and when combined with PRRS and influenza, it's an utter disaster.

If it is an uncomplicated mycoplasma in a stable farm, there will still be a decrease in performance, Bruner says. While you might not be able to see the pigs getting sick and only hear a cough, you will likely have a decrease in performance.

Economically, mycoplasma can increase mortality in wean-to-finish pigs. It can be as little as 2%, but it can go as high as 10%, especially when it’s combined with PRRS and influenza. When SVC looked at its client base, and combined the average daily gain, feed efficiency and mortality, it adds up to about $3.61 per head. Bruner says that's conservative; if you add PRRS on top of that, it can be worse.

To be or not to be
When it comes to mycoplasma, Bruner says there are really two options: be positive stable or negative. There are a few reasons to remain mycoplasma-stable:

  • If it’s an unfiltered sow farm in a pig-dense area
  • If chance of break-back is high
  • If farrow to finish is on one site

Bruner says it is possible to have OK production from a mycoplasma-positive farm, but the veterinarian does have some non-negotiables when it comes to that.

First, it must be a PRRS-negative, wean-to-finish herd. There also needs to be good early gilt acclimation. That means gilts getting infected around 84 days of age, so they have time to decrease shedding, and stop by the time they have a litter.

Finally, there needs to be a good vaccination program, with a couple doses of mycoplasma vaccine getting into the growing animals.

Mycoplasma-free is best
In Bruner's opinion — one that seems to be consistent with many SVC clients — a mycoplasma-negative status herd is the most desirable. SVC recently took a poll of its top 16 sow clients, and 80% of those farms are mycoplasma-negative. SVC has eradicated mycoplasma from nearly 200,000 sows.

"There are a few exceptions with the continuous flow and the really pig-dense areas and non-filtered we may run them positive, but in general life is much better mycoplasma-negative," Bruner says.

In order to get a herd to mycoplasma-negative status, SVC conducts an eradication process that involves exposing all the animals to mycoplasma, closing them down for an eight-month period, and most times at the end, doing a medication phase.

Bruner says after the process, the producers typically see higher average daily gain, lower mortality and decreased medication costs: overall, an easier pig to raise.

Keeping negative
The most likely routes of reintroduction into sow farms is either aerosol or gilt introductions. Filtration has worked well in keeping mycoplasma out but is not an option for every site. That's where keeping it out via gilt introduction becomes crucial, Bruner says.

A common testing procedure SVC and its clients conduct, is if they’re entering them as feeder pigs, coming in around 50 pounds, those pigs will be isolated for three weeks, SVC will do 30 laryngeal swabs and pool samples into three for mycoplasma polymerase chain reaction, which detects the presence of DNA in the bacteria.

This saves on cost, so the producer pays for 10 tests versus 30, and it doesn't decrease sensitivity significantly. 

"If you're a multiplication farm, you might want to consider testing them out of the nursery," Bruner says. "For most of our clients, we test them once they get to the on-site isolation. As a feeder pig, we wait the three weeks to give it time. If it did get infected in a late nursery or on a truck, there's time for the mycoplasma to spread, and then we'll do 30 samples of laryngeal swabs."

If SVC has a client that is bringing in selects, the veterinarians will do the same testing with the laryngeal swabs, but prior to entry into the farm. Once they get to the on-site isolation, the team waits three weeks and does the testing again.

"They'll get tested twice before they're actually brought into the farm, if they're brought in as selects. We like to get that testing done within a week of shipment," Bruner says. "We have a seven-day rule. If they're going to get on a truck, they have to be tested within seven days of movement."

Since serology results are generally four to six weeks behind infection and will not pick up acute breaks, that testing doesn't fit with SVC's three-week isolation period before bringing gilts into the herd. With the saliva-rope test, there is very low sensitivity, and it's often likely a mycoplasma break will be missed.

Taking a tracheal sample or a laryngeal swab are the two testing methods that seem to work best. SVC has chosen the laryngeal swab on most of its herds, because it's easy to train people on and relatively simple to get.

Responsive monitoring
For their mycoplasma-negative sow farms, Bruner says there's not a lot of ongoing monitoring that must be done. It's more responsive.

"If there's a cough on a sow farm, I will typically test for flu and mycoplasma," Bruner says. "If they look at me wrong, if they give me one cough, they're getting the laryngeal swab for sure — we have a pretty heightened sensitivity to coughs on sow farms. We want to make sure we didn't get a new introduction in."

The team will also do serology on those farms, just in case it's an infection that's been there for a while and was not caught. Bruner says it also adds another layer to the testing; and if it's positive, they'll know that it's been there for four to six weeks.

If there is an unexpected cough in the nursery — and even if it's less frequent — SVC will still do some testing for influenza and mycoplasma. The same goes for grow-finish herds.

If a cough starts mid-finishing, the SVC team will use ropes to collect fluids for flu testing, and if negative for flu, will then move to laryngeal swabs to make sure there isn't instability on a sow farm somewhere up the chain.

Getting it right
Monitoring aside, Bruner says the process really comes down to the right test at the right time, and getting the right sample.

"I believe that's the right way to test for incoming gilts into your farm, and mycoplasma-negative status is worth it," Bruner says.

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