Mycoplasma hyopneumoniae elimination becomes possible

Paul Yeske discusses Mycoplasma hyopneumoniae eliminate

Over the past two decades, the swine industry learned how to eliminate Mycoplasma hyopneumoniae (Mhp) from herds without depopulation/repopulation, according to Paul Yeske, DVM, Swine Vet Center, St. Peter, Minnesota. Yeske has been at the forefront of the efforts to eliminate the respiratory disease for clients.

The move to eliminate Mhp from herds has “really picked up momentum in the last 4 to 5 years,” Yeske added in an interview with Pig Health Today. In fact, efforts are underway to work towards areas or regions in Minnesota that are Mhp-free, with the end goal being the elimination of the disease from the state.

Why elimination?

When the industry moved toward high-health status sow herds, instability increased when Mhp-negative replacement animals entered positive herds and became infected just before farrowing, Yeske explained. Maintaining an Mhp-stable herd was a lot of work because the organism is very slow and takes a long time to infect animals and you must be deliberate in every step of the process. It also takes a long time for Mhp to clear from animals – up to 240 days. Gilt replacements need to be exposed by 80 days of age so they are not shedding the Mhp when they farrow.

As a result, many producers decided to eliminate it from their systems. Yeske noted that once a system has a good gilt-stabilization program, the herd is also set up well to go on to an elimination program.

“The herds we stocked that were negative from the beginning showed us the advantages of negative production,” he explained. “If you look at the literature, [the cost of Mhp] is anywhere from $2 to $10 a pig, and the average probably being in that $5 range. We know there’s a significant cost and a significant return.

“If we do a long-term closure, we’re talking about somewhere in that 3- to 4-month payback,” he continued. “If we do a heavy medication program and no closure, we’re talking about an 11- to 12-month payback.”

In addition, eliminating Mhp takes away the “add-on effects” when a herd experiences other infections like influenza and porcine reproductive and respiratory syndrome (PRRS) which can be even more costly.

“Producers have taken the approach —  ‘let’s take one off the table because we can’,” he said.

Statewide elimination efforts

Leading the work to eliminate Mhp from Minnesota is Maria Pieters, DVM, University of Minnesota. Yeske said the plan is in its early days but hopefully they’ll be able to get more herds involved and help reduce the potential for lateral risks of Mycoplasma spread.

“But it’s like any other voluntary program…there’s always going to be some period of time for adaption,” he said.

He doesn’t expect that in five years Mhp will be eliminated, but “hopefully at some point, I can still come back to the Leman Conference and say, ‘We used to have Mycoplasma‘.”

More accurate gilt testing needed to detect Mycoplasma hyopneumoniae

Listen to the podcast


Sow herds seeking negative Mycoplasma hyopneumoniae (M. hyo) status should use accurate gilt surveillance methods.

Research conducted by Alyssa Betlach, DVM, veterinarian with Swine Vet Center and graduate student at the University of Minnesota, showed differences in the ability to detect a recent M. hyo infection based on sample types used.

“My research is focused on replacement gilt populations and really ensuring, if there was a recent introduction of M. hyo, were we able to detect such introduction with the commonly utilized practices we do today,” Betlach explained.

Maintaining a negative health status for M. hyo in the sow herd is important for reducing the economic toll that this pathogen has on hog production.

Detection differences based on sample type

In the research trial, a naturally infected gilt was introduced into a naïve population. The group was tested periodically for M. hyo using blood samples, oral fluids and other sampling methods including laryngeal swabs and deep tracheal catheters.

“There was one new naïve gilt that became positive at 6 weeks after contact, so you can appreciate that there’s a very slow transmission of M. hyo compared to other pathogens,” Betlach said.

The blood tests did not detect the naturally infected gilt until week 6. But the laryngeal swabs and deep tracheal catheters detected the infected gilt from the beginning of the trial. Oral fluids remained negative.

Different mindset required

The laryngeal swabs and deep tracheal catheters are relatively new sampling techniques. Both require training and practice but are more accurate than other sample types during the early stage of infection.

“If we really want to increase our ability to track M. hyo, we need to have a different mindset and focus in on more sample types that are more sensitive for detecting such pathogens.”

Producers should also understand the advantages and limitations of each sample type and make adjustments as needed in gilt surveillance.

“You could think about even extending your isolation period if you want to take a different sample or less sample sizes,” Betlach suggested.  

The end goal is achieving and maintaining a negative health status in sow herds.

Gilts and sows have a critical role in the transmission of M. hyo. “So it’s really important to minimize the introduction of it…to reduce the cost of M. hyo,” she said.




Maintain mycoplasma-negative herds with laryngeal swab tests from incoming gilts


Sow farms that have eradicated Mycoplasma hyopneumoniae (M. hyo) must continue surveillance to keep the pathogen out or the results will be devastating, according to Laura Bruner, DVM, Swine Vet Center (SVC), St. Peter, MN.

“The most common entry is usually gilt introduction,” she said. “Mycoplasma can enter through the air but is less frequent.”

Right test for surveillance

Historically, serology tests were used to see if the incoming gilts were negative to M. hyo. But those tests are six weeks behind the infection, Bruner claims.

“In serology, we’re really looking at antibodies,” she explained. “Mycoplasma is a little bit unique in that we don’t start seeing antibodies in the serum until somewhere 4 to 6 weeks post-infection so I’m going to miss a really acute infection or a recent infection.”

Now she uses laryngeal swabs and M. hyo PCR (polymerase chain reaction) test to look for the actual bacteria in gilts. Bruner’s SVC colleague Alyssa Betlach, DVM, made this determination after conducting research to find the most accurate test and protocol for finding M. hyo in gilts.

“The laryngeal swabs tested for mycoplasma with PCR means we’re actually looking for the bacteria versus the response (to the bacteria) like serology does,” Bruner said.

Sampling techniques

The laryngeal swab requires a speculum to open the mouth and take a saliva sample from the larynx where saliva builds up. Bruner uses a regular spoon with an extension to collect the sample.

“We’re going closer to the respiratory tract and pulling out saliva that we can test for the bacteria,” Bruner said. “Ropes have been used in the past for mycoplasma, but the sensitivity is not very good… It does not pick up infections as well as laryngeal swabs.”

When a group of gilts comes into a facility, Bruner tests 30 animals and pools the tests into groups of three for a total of ten PCR tests.

The results?

Since implementing the test a year ago, she’s encountered a few suspects, but none positive to M. hyo. When she has a suspect test result, she goes back a week later and takes 60 samples, either laryngeal swabs or deep tracheal samples.

Testing for mycoplasma is not limited to gilts. “If we hear coughing on the sow farm, that will prompt us to test for mycoplasma, using the same method of the laryngeal swabs,” Bruner said. The same goes for early- or mid-finishing pigs. If a test is positive, she will go back to the sow farm and do more testing.

Bruner and her colleagues have conducted mycoplasma eradication on nearly 200,000 sows with an 80% success rate. These new surveillance protocols will help keep the successful herds negative.


Mycoplasma elimination possible, but more difficult on farrow-to-finish sites

With the right program in place, eliminating mycoplasma pneumonia is possible on many hog farms. Farrow-to-finish sites are still the most difficult to clean up, however, reported Swine Vet Center’s Paul Yeske, DVM.

He has carried out multiple mycoplasma-elimination efforts on different types of hog farms with good success.

“The farms that are easiest [to eliminate mycoplasma] are the farms that are multi-site production, where we have a farrow-to-wean site…The herds that have all ages of pigs on site, that’s where the challenge is going to be,” he said.

Long-term herd closure

The best method for eliminating mycoplasma from a farrow-to-wean site requires herd closure to allow the animals to develop immunity and stop shedding. Research shows the disease’s causative organism, Mycoplasma hyopneumoniae, can be shed up to 240 days.

“We expose all the animals up front to make sure everybody’s exposed and immune, and then we wait 240 days,” Yeske explained. “At the end, we use some medication as a secondary step to make sure we’ve controlled everything before we bring the negative animals back in.”

The advantage of this elimination program is a short payback period of a few months, he added. A depopulation-repopulation elimination takes a couple of years to pay back the expense.

Farrow-to-finish options

Farms with all ages of pigs on one site require more time and expense to eliminate mycoplasma. A partial depopulation that empties the nursery and finishing stages for a short time is one solution, according to Yeske.

“I think there are ways we can do [elimination] on really any given farm,” he said. “It’s just finding creative ways to do it. And the depopulation-repopulation would certainly be an option.”

Complete elimination

Could mycoplasma be completely eliminated from US herds?

“I think it’s a disease that could be eliminated,” Yeske stated. He cited research that showed a low likelihood of M. hyo reinfection from neighboring finishing units.

“If you have a mycoplasma problem in your system, you likely have a system problem,” he said. “It’s not the neighborhood problem.”

Plus, the future holds new technologies like better diagnostics, new antibiotics and new testing procedures.

“Are there ways we can manipulate these tools to eliminate disease so we don’t have to deal with it?” he added. “What I’ve tried to do over time is, when something new comes out, [to determine] how could we leverage this into a new tool.”

In the past, the pork industry has eliminated diseases like pseudorabies without depopulation-repopulation.

“We had a very good vaccine with pseudorabies, and we were able to do eliminations by test and removal,” Yeske recalled. “Mycoplasma is another bug that lends itself well to herd closure and elimination.”

Watch the interview with Pig Health Today:

Gilt acclimatization is key to eliminating Mycoplasma hyopneumoniae in sow herd

Successful elimination of Mycoplasma hyopneumoniae (M. hyo) from a herd is often driven by sow farm status, according to Alyssa Betlach, DVM, Swine Vet Center. Betlach has researched M. hyo for several years in a PhD program at the University of Minnesota.

Within the industry, M. hyo continues to be a prevalent and economically important respiratory pathogen worldwide. Studies have shown that the disease can add $3 to $10 per pig due to decreased animal performance, including longer time to market and increased antimicrobial usage, she added.

Traits of M. hyo

Three unique features of M. hyo must be considered when developing a control plan. First, piglets are not born with M. hyo but often are colonized from their mothers, who shed it during farrowing. The bacterium colonizes in the lungs of the pigs and causes clinical signs in grow-finish due to the slow, chronic nature of the infection.

Second, M. hyo primarily resides in the respiratory tract by adhering to lung cilia.  Therefore, “When you think of diagnostics and sampling, you need to consider that it resides deep in the lung,” Betlach said.

Third, shedding from M. hyo has been shown to last up to 240 days and transmission is very slow. One pig needs 4 to 6 weeks to transmit the disease to another pig versus the flu that is transmitted from one pig to 14 others in a 2-week period.

Elimination starts on sow farm

Current elimination programs have successfully removed M. hyo from many herds. But the methods for elimination continue to improve by focusing on gilt acclimatization and sow farm stability.

“We need to think about negative gilts,” Betlach said. “If you have a positive farm and you constantly bring in negative gilts, you are adding wood to that fire. Therefore, we need to think of ways to address this.

“Gilt acclimatization is something we should think about,” she continued. “Gilt acclimatization strategies are designed to stabilize the sow herd by promoting ways to minimize shedding at farrowing.”

Acclimatizing gilts

Three types of gilt acclimatization are used, namely vaccination, natural exposure and exposure using a herd-specific lung homogenate. Vaccination for M. hyo is commonly practiced as it can reduce the bacterial load and clinical severity. However, M. hyo vaccination does not prevent colonization and has minimal effect on altering transmission.

Natural exposure through the introduction of M. hyo-positive culls into a gilt development unit has been performed. However, this approach is less than ideal in larger herds, as it takes a long time for adequate exposure and requires a high number of positive culls. Studies have shown that it takes one positive cull to one or two gilts for successful exposure within a 4-week period.

Exposure using a herd-specific, M. hyo-positive lung homogenate has been performed in the field, via intra-tracheal or aerosol techniques. Intra-tracheal exposure is a more labor-intensive method and may not be as feasible in large populations, as approximately 50% to 70% of the herd will need to be exposed to be successful. Therefore, aerosol exposure using foggers has been explored. Recently, this method has been shown to be successful for M. hyo exposure while being more feasible to perform.

Diagnostics for M. hyo

Several sample types are used for the detection of M. hyo. It is important to consider the overall goal that you are trying to achieve, as this will determine what sampling method should be used.

“Serum is commonly used, and the cost is relatively low,” Betlach said. “This sample type is used to detect the presence of M. hyo antibodies and it is easy to collect. However, the ability to interpret diagnostic results can be difficult, especially in vaccinated herds as the presence of antibodies from the vaccine or infection cannot be differentiated.”

Other sample types, such as oral fluids, laryngeal swabs and tracheal sample, are used to detect the presence of M. hyo infection. Oral fluid samples are easy to take, and the results are easy to interpret, in most conditions. Oral fluid samples work best in chronic situations but are not sensitive enough to detect the pathogen in an acute infection.

Laryngeal swabs, which are convenient, require some employee training. Positives can be obtained at 7 to 14 days after infection, Betlach said. In comparison, tracheal samples appear to be more sensitive in acute and chronic situations. This sample type also requires additional training as false-negative results from poor sampling technique can occur. Due to their sensitivity, Betlach uses tracheal samples in elimination strategies.

“Diagnostics have improved over the years,” she added. “For M. hyo detection, it is critical to think about what sample type you are going to use and the time of infection, and to understand the question you want to answer.”



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.

Gilt acclimatization, reduced shedding keys to curbing downstream M. hyo disease

By Paul Yeske, DVM
Swine Vet Center
St. Peter, Minnesota


Research shows that if more piglets are positive for Mycoplasma hyopneumoniae (M. hyo) at weaning, there will be more problems in finishers, with decreased average daily gain, increased mortality and poor feed conversion.1 There will be a lower percentage of pigs sent to the primary market as well as higher treatment costs.

The costs of M. hyo can really add up. When actual production numbers from 2007 to 2015 are plugged into an economic model, the cost is $4.99 per pig.2 Data from other farm systems indicate it’s $2.85 per pig.3

To reduce the amount of downstream disease in pigs, we need to reduce the amount of M. hyo shedding. This begins with proper acclimatization of gilts going into the sow herd, which is a challenge.

Negative gilts present challenges

Historically, most replacement gilts were born into positive herds, or they were raised internally in the herd and were infected early in life. They had plenty of time for shedding to minimize before farrowing, which helped keep herds stable for M. hyo. By stable, I mean a low percentage of weaning-age pigs are positive for the pathogen within the respiratory tract.

Today, most replacement gilts are negative for M. hyo and aren’t acclimatized until they get to the sow farm. Therefore, the first challenge is getting them infected within a reasonable time frame.

Gilts need to be brought in at a young enough age so there’s enough time following infection for M. hyo shedding to decline. This is critical whether you want to stabilize a positive sow farm and reduce the impact of clinical disease in the finishing phase or if your goal is herd closure and M. hyo elimination.

Ideally, negative gilts would be infected by 84 days of age. Figure 1 demonstrates the time needed to reduce shedding in farrowing gilts and their piglets.


Figure 1. Gilt Mycoplasma hyopneumoniae exposure timeline


Gilt-exposure methods

There are several methods of exposing negative gilts:

  • Use seeder animals, an approach that’s been utilized in the industry for a long time. It works well if the right animals are used and there’s plenty of time — but it can also be difficult.To achieve a shorter time for infection, such as 30 days, six seeders for every four naïve gilts is needed to be 100% successful. However, if the infection in the seeders dies out, it can be difficult to get the acclimatization program restarted. The result can be problems with M. hyo in finishers and lost performance during the process, and it may take time to re-establish herd stability.
  • Intratracheal inoculation is another way to acclimatize naïve gilts and has been explored in the research arena. I wouldn’t recommend this method because it’s labor intensive and it can pose a danger to staff since restraint of gilts is necessary.
  • Aerosol inoculation is new technology that’s been used in other species for vaccination and may be a possibility for hyo acclimatization of gilts. It’s less labor intensive than intratracheal inoculation and animals don’t have to be restrained. There are some technical steps required. For example, it has to be done in an area with small air space. If you want to consider this approach, it’s imperative to work with your herd veterinarian so all the technical details are addressed.

One of the keys to successful acclimatization is having a good diagnostic protocol to confirm that gilts have in fact been properly exposed. Toward this end, testing every group of exposed naïve gilts is key, whether your goal is M. hyo herd stabilization or elimination.

Considering elimination?

M. hyo elimination is possible using a combination of herd closure, vaccination of the breeding herd and medicating of the breeding herd as well as piglets. Infected piglets also can be treated individually with an injectable antibiotic to help reduce the impact of the disease.

Elimination is recommended when it becomes a struggle to get gilts exposed on a consistent basis, for herds in a filter project and when producers simply become tired of dealing with costly M. hyo clinical problems.

If you’re considering M. hyo elimination, one of the first questions to ask is whether it really will be worthwhile. This might not be possible for farms located in pig-dense areas where reinfection is a strong possibility. However, when we followed 100 sites in pig-dense areas throughout two seasonal periods, we found only 6% of the sites were positive for M. hyo from lateral-source introduction.

Summing up

Proper gilt acclimatization is key to successful herd stabilization and M. hyo management. This applies whether your goal is to stabilize the herd and minimize the load of M. hyo in weaned pigs or to eliminate M. hyo.

A good diagnostic plan is essential. Every group of gilts that enters the herd must be checked after exposure to ensure proper acclimatization. Unfortunately, it takes time, especially in herds receiving adult replacements. Acclimatization of gilts is also more challenging today because most replacement gilts are M. hyo-negative.

Lateral transmission does occur, but it’s not very frequent.  If you are having a problem controlling M. hyo in a herd, it’s likely a problem originating from the source sow herd and not the geographic area.

You’ll have better results managing M. hyo if you work with your herd veterinarian to develop an individualized plan.



Editor’s note: The opinions and recommendations presented in this article are the author’s and are not necessarily shared by the editors of Pig Health Today or its sponsor.





1. Schwartz M. Cost of M. Hyopneumoniae in growing pigs. 2015 Allen D Leman conference.
2. Linhares D. A field study on economics of Mycoplasma hyopneumoniae elimination. 2017 Allen D Leman conference.
3. Yeske P. Mycoplasma hyopneumoniae Elimination. Proceedings from AASV annual meeting. 2016:376-381.