M. hyo: The Uninvited Guest

For most pork production facilities, Mycoplasma hyopneumoniae, commonly known today as M. hyo, is an uninvited, permanent guest. This organism is a major cause of pneumonia, and it is found nearly everywhere, waiting to infect pigs by itself or, more often, piling on when pigs are already fighting other respiratory ailments.

M. hyo often occurs simultaneously with other viral infections such as porcine reproductive and respiratory syndrome or swine influenza virus, increasing the severity of both while greatly complicating your pigs" health. But it's fully capable of causing damage on its own.

"Nearly all the farms in our practice area have M. hyo," says Norman Hansmeyer, DVM, Winfield, Iowa. "I would say it's next to impossible for a farm to remain M. hyo-free."

The challenge increases as Mycoplasma pneumonia cases occur throughout the year. You should suspect the disease when pigs have a dry, non-productive cough that's most pronounced when they are first stirred from rest and then persists over a period of time.

However, since the widespread use of porcine circovirus vaccines, Hansmeyer believes M. hyo causes less havoc.

Still, M. hyo infections challenge pigs and producers alike. "It appears we continue to have significant problems with Mycoplasma pneumonia in the mid- to late-finishing phases," says Alex Ramirez, DVM, Iowa State University Veterinary Diagnostic Laboratory.  "Recently, it appears that late-finisher breaks are even more common."

With most commercial herds positive for M. hyo, the two-way vaccine (PCV2 plus M. hyo) has helped keep a lid on virulence of the disease. If present in high-health herds, it's quite manageable when not complicated by concurrent infections. However, when other factors come into play, such as a variant strain of PRRS virus, the Mycoplasma infection will likely cause more damage and will be more difficult to control.

"Swine influenza virus is another complicating factor when present with Mycoplasma, " says Lisa Tokach, DVM, Abilene Animal Hospital, Abilene, Kan. Tokach sees Mycoplasma most often in the early finishing period, or in 80-pound to 120-pound pigs.

"M. hyo is definitely still around but due to producers" widespread use of M. hyo vaccines our ability to control the disease has improved," Tokach says.

Since October 2011, the Iowa State Veterinary Diagnostic Laboratory has recorded a significant increase in PRRS case submissions, which is likely to drive up Mycoplasma pneumonia diagnosis.

Farms in Hansmeyer's practice saw a spike in swine influenza outbreaks as well as PRRS in mid-to-late December, and he believes it's very difficult to keep pigs free of respiratory disease. "With 1,000 to 2,000 or more pigs all sharing the same air space, respiratory disease is easily transmitted throughout the barn," he says.

All-in/all-out production is a powerful tool to control and reduce Mycoplasma pneumonia severity, says John Baker, DVM, Warrick Veterinary Clinic, Boonville, Ind. Removal of potential M. hyo-carrier animals and barn sanitation between pig groups both play important roles in reducing incidence of the disease.

"Mycoplasma incidence in our practice is about the same as we've seen in recent years and is under control for most herds," Baker says. "That's probably because we have PRRS under control for most of our clients."

Farms struggling to control M. hyo have an unstable Mycoplasma status in their sow farms caused by adding Mycoplasma-free breeding stock to M. hyo-positive sow herds, Baker believes.  "These animals are not being adequately immunized prior to entering the sow herds," he adds. 

The solution: Don't introduce gilts with low immunity levels into a Mycoplasma-positive sow farm. "When we added gilts from Mycoplasma-positive finishers that were vaccinated at an early age, they entered the sow farm with low infection levels and high immunity levels," Baker notes. This resulted in less shedding of the organism and more immunity passed to their offspring.

"In cases where incoming gilts are still clinical with Mycoplasma when added to the herd, they could destabilize the sow farm and result in increased shedding," Baker says. In these situations, he suggests blanket vaccination of the gestation herd to build immunity and reduce the shedding.

Baker also warns against holding slow-growing hogs back in the finisher while young pigs are being placed. "This is a sure way to maximize young pig exposure and can result in economic loss to this disease," he points out.

Economic loss related to M. hyo varies according to the growth stage when it's introduced. "Mycoplasma is a slow-growing organism, so by the time we're working on treatment, it's already been causing issues in the pigs for several weeks," Ramirez notes.

Your veterinarian can submit necropsy tissue samples for a laboratory diagnosis. "A Mycoplasma diagnosis can be confirmed by demonstrating seroconversion two to four weeks prior to the onset of the clinical signs," Baker says. 

 Slaughter checks can assess disease severity and the economic loss, but this has to be interpreted along with clinical presentation of the disease within the herd, Baker says. For example, late infections may reveal significant damage during a slaughter check yet not cause extensive economic impact. 

Herds with early clinical signs at 8 to 12 weeks of age may have the greatest economic loss. However, lung lesions at slaughter from these pigs are mild because they have had time to heal, Baker adds.

Identifying concurrent infection with other organisms is crucial to successful treatment. Since other common issues include Pasteurella, Bordetella, Strep suis and Haemophilus parasuis, a necropsy and diagnostic test are necessary to understand the dynamics of the infection. "Mycoplasma outbreaks are most successfully treated based on an understanding of the co-infection that the animals are facing," Baker says. 

A herd that's experiencing clinical Mycoplasma can be managed with strategic antibiotic application, usually in the feed. To treat M. hyo-infected pigs in the finishing stage, Hansmeyer usually relies on in-feed antibiotics. For late-finishing hogs, he suggests treatment in the feed or water on a herd basis.

Filtering incoming barn air when combined with a thorough biosecurity program provides protection from Mycoplasma as well as PRRS. (For more information, go to http://bit.ly/sGBsBL.)

 While air filtration has shown effective results in preventing disease, it's not yet widely used in finishing facilities. "Filtration has not been adopted in my area due to our low PRRS incidence," Baker says. "I would assume if it prevents infection with PRRS virus it would also prevent Mycoplasma introduction."

Meanwhile, vaccination offers effective prevention against Mycoplasma. "I am a strong believer in vaccination," Ramirez says. "While it appears commercial vaccines are effective in minimizing clinical disease, vaccination timing is key." 

Work with your veterinarian to refine the timing for each particular case.  "A blanket protocol simply will not work for all farms," Ramirez adds. "For example, vaccinating at the time of PRRS seroconversion minimizes Mycoplasma vaccine's effectiveness."

Baker estimates that about 20 percent of farms in his area could do a better job of controlling Mycoplasma in finishing pigs if they adjusted their vaccination and medication program.

"Most of our clients have been using a two-dose vaccine, with good success," he says. "The vaccination schedule we recommend depends on the operation, its flow and health challenge. Most of the herds we work with use a two-dose protocol, usually at weaning and two to three weeks later."

In herds that still have problems with Mycoplasma, Baker recommends giving the first vaccine dose at 3 to 5 days of age.

"I want to build as high a wall of immunity as early as possible before the pigs are exposed to the organism," he adds.

In cases where there seems to be significant Mycoplasma shedding from sows to their pigs, Baker recommends vaccinating sows four to six weeks before farrowing.

Hansmeyer recommends a porcine circovirus-M. hyo vaccine and vaccinates baby pigs with the first dose at weaning age and a second dose two to four weeks later. The exception would be in piglets nursing sows with a low level of maternal antibodies. Those piglets receive their first dose around 5 to 7 days of age and a second dose at weaning.

Tokach recommends the first dose be administered prior to weaning and the second in the nursery about three weeks later. Some of Tokach's clients get by with just one dose. However, late Mycoplasma breaks may occur as this regimen may not provide adequate duration of immunity, she adds.

Many factors are involved in controlling Mycoplasma. But by carefully reviewing vaccination and treatment strategies with your veterinarian, you can increase the prospect of success against this uninvited guest.



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