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.”



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.