By itself, mycoplasmal pneumonia is mostly a nagging disease. When it teams up with other diseases, things get ugly.

A few years ago you might not have worried too much about mycoplasmal pneumonia. But it’s rapidly becoming a major player in respiratory disease problems for finishing pigs. With new diseases like porcine reproductive and respiratory syndrome, getting an accurate diagnosis is the new challenge.

“Pure Mycoplasma hyopneumoniae infections have little effect on pigs’ growth rates,” says veterinarian Kirk Clark, Purdue University. “However, clinical expression of the disease is usually exacerbated by secondary infections. Pasteurella multocida is one such culprit, causing high fever, thumping and death if pigs aren’t treated.”

In segregated early weaning systems, mycoplasmal pneumonia can be eliminated or at least downgraded to a subclinical state, Clark says. That’s often the case in all-in/all-out systems. But he warns that if you’re trying to use SEW protocols in older, converted buildings where you face limitations, mycoplasmal pneumonia can become clinical in some pigs. That’s when mycoplasmal pneumonia may initiate porcine respiratory disease complex which spreads to other disease-naive pigs.

The real problems continue to occur in continuous-flow finishing units where older pigs keep Mycoplasma cycling to young, incoming pigs.

If you suspect your pigs are infected with Mycoplasma hyopneumoniae, here are a few suggestions:

- Assess the prevalence of mycoplasmal pneumonia and its effect on your herd.

- Assess whether you can implement either all-in/all-out or SEW technologies. If you can, work with your veterinarian and begin the process.

If not, consider using the mycoplasmal pneumonia vaccines to reduce the problem in your herd. Of course you’ll need to evaluate whether the vaccination program is likely to be cost-effective.

- Even if you operate on an all-in/all-out or SEW schedule, you may need to use vaccines in a strategic manner.

- Eventually immunize the whole pig population to reduce disease shedding.

- If you think you have respiratory diseases in the finisher, start doing regular post-mortem examinations.

- Have slaughter checks conducted to obtain a good look at the condition of your finishing pigs’ lungs.

- Have your veterinarian do serology testing to determine when mycoplasmal pneumonia occurs in your herd so you have an idea of when and where it’s going to hit.

Don Bowden, a Winthrop, Iowa, veterinarian, suggests drawing blood from various ages of pigs to see where disease titers are highest. He emphasizes that the pigs were probably infected two to three weeks prior to testing positive with the serology test, so plan vaccination protocols accordingly.

“With porcine reproductive and respiratory syndrome coming into herds, it makes pigs more vulnerable through reduced immunity or stress, making Mycoplasma a big factor in the whole disease process,” Bowden says.

He cites an example which demonstrates the problems mycoplasmal pneumonia creates. He did serology work on two finishers, one with 1,000 head and the other with 1,200 head. He found that some of the pigs weaned at 18 days and sent to an off-site nursery tested negative for Mycoplasma. At eight weeks, they were moved all-in/all-out by room into a finisher. Within each building there were four different age groups.

When those pigs reached 16 weeks of age, they tested PRRS-positive but were negative for Mycoplasma. But by 18 weeks, the pigs showed up with clinical cases of mycoplasmal pneumonia.

Bowden believes the problem occurs because disease-naive pigs went into the finishing units while others were shedding the Mycoplasma organisms. The fact that the finishers weren’t running through an all-in/all-out pig flow contributed to the problems. 

The hogs typically headed for market at 24 to 26 weeks of age. During the last six to eight weeks that the pigs were in the finisher, Bowden says, about half of them were unaffected by Mycoplasma, about 25 percent were infected, and another 15 percent to 25 percent required two to three weeks longer to reach market weight.

There is no cure for mycoplasmal pneumonia, but the available vaccines help control the disease.

“We have several good vaccines on the market that help tremendously,” says Pat Halbur with the Iowa State University veterinary diagnostic lab. “The vaccines are among the most cost-effective products available, but they do sometimes fail.”

It’s a matter of figuring out which one works best for your operation, Halbur continues. “Try one. If it doesn’t work, try a different one. There also are some good feed medications available.” A combination of vaccines and feed medications may be required. “Eventually you can eliminate one or the other.”

While the vaccines show positive results, there are some drawbacks. Eileen Thacker, Iowa State University immunologist, says of those available, there are still some unanswered questions, especially about how long they last. For instance, if a pig is vaccinated at three and seven weeks of age, will the vaccine protect it against Mycoplasma through the finishing stage?

“One of the problems I see is when pigs have had mycoplasmal pneumonia for a long time, they stop having detectable antibodies in their blood,” Thacker notes. In a sow herd low-parity sows have high levels of Mycoplasma antibodies, while older sows have lower levels. It’s difficult to develop a vaccination schedule for these different sow types, she says. So you may end up with subpopulations of pigs that get infected.

“Of the four vaccines that I’ve tested, all reduce lung lesions from a level of 12 percent in unvaccinated hogs to about 3 percent in pigs vaccinated twice,” Clark points out.

He adds that the vaccines do not eliminate the disease or the cough from pigs, but vaccinated pigs usually reach market weight at least 10 days sooner. And in some cases, they require less feed per pound of gain.

“Vaccines need to be used differently in different management systems. But when pigs take longer than 180 days to reach market weight and you observe coughing in the finishing stage, vaccines appear to be cost-effective,” Clark says.

Results from the various vaccines will differ depending on your management system and the secondary diseases in your herds.

Bowden suggests starting a vaccination program based on the point at which your herd is being exposed. By doing this, it will take about six months to get the entire population vaccinated, but it should address about 85 percent of the problems you had prior to vaccinating.

The most important thing to do is confirm the diagnosis of mycoplasmal pneumonia. “The days of adding more vaccines and drugs to treatment regimes are over,” he says. “It’s more economical to do the diagnostics, find out what’s there and how to treat it.”

“Not only do you have to determine whether your herd is infected,” Bowden says, “but you need to consider how much it’s costing you and how much you can afford to spend to prevent it. That means you’ll need records.

“Death loss isn’t a big factor with mycoplasmal pnuemonia, but loss of production is – especially lightweight hogs leftover at the end of the finishing group. When you mess up pig flow and have to sell lightweight pigs, that’s where Mycoplasma costs you money.”

A Nuts And Bolts Look
Mycoplasmal pneumonia is the most widespread pneumonia of pigs in the world, says veterinarian Kirk Clark, Purdue University. The disease is usually transferred to growing pigs by the sow if they’re weaned at 21 days or older.

Another transmission route is via contact with infected older pigs in the finishing building.

If you run a continuous-flow finishing unit, infected pigs will start coughing when they have been in the unit three to four weeks. This is the clinical stage. Some pigs may continue coughing for six to eight weeks, Clark notes. Since all pigs aren’t exposed at the same time, the coughing may continue all the way through the growing phase.

In continuous-flow buildings, pigs usually contract the disease when they are 12 to 14 weeks old. That’s because the rooms aren’t cleaned out and there’s increased exposure to older hogs. All-in/all-out pig flow systems can help control the disease. If a break occurs, figure that exposure occurred four or more weeks earlier, Clark adds.