How long do mycoplasma-negative herds stay negative?

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Most hog farms successfully stamp out mycoplasma pneumonia when they work with their veterinarian to eliminate the disease. The challenge is preventing reinfection.

If the herds remain negative after the first 8 months, they became reinfected at a much slower rate over a much longer time than the herds turning positive in 8 months, reported Paul Yeske, DVM, Swine Vet Center, St. Peter, Minnesota.

Yeske and his colleagues looked at all the clinic’s herds taken through a mycoplasma-elimination program. They rated the success of each effort and plotted over time when the herds turned positive, which they called the decay rate.

81% elimination success

They noted a distinct difference between herds that used a closure plan with medication (water medication for sows and injection to piglets) for the elimination versus just medication (injection of both sows and piglets).

“On herds using a closure and medication plan, we were 81% successful,” Yeske said. “In herds with medication and no closure, we were at 62% success.”

The clinic’s protocol for whole-herd elimination required all pigs on the farm to receive a vaccine injection followed with a second dose 2 weeks later. In elimination with no herd closure, animals that become infected with mycoplasma can shed the organism for up to 8 months.

“I believe what happens with no herd closure is some of the herds decay rapidly because we never got mycoplasma totally eliminated,” Yeske said. “If they make it to 8 months, the pigs were done shedding and the herd was able to stay negative going forward.”

More negative herds in future

“Mycoplasma elimination is one program that’s been widely done in a relatively high number of herds and has been successful. I think we will see more and more people adopt elimination and see more herds go to mycoplasma-negative pigs because of the economic benefits with grow-finish production,” he explained.

“The good thing with mycoplasma is we have the tools to eliminate and successfully keep it out of our herds for a long time.”

 

Lessons learned from recent Seneca Valley outbreaks

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The Seneca Valley virus (SVV) is proving to be something of a test case for swine producers’ and veterinarians’ preparedness for foreign animal diseases (FADs).

While SVV is not an FAD, nor does it pose a harsh economic penalty for infected herds, the virus does produce lesions on the pig’s snout, feet and coronary bands that are indistinguishable from FADs, particularly foot-and-mouth disease.

Last summer, Jake Schwartz, DVM, Swine Vet Center, St. Peter, Minnesota, spent time investigating SVV outbreaks in Nebraska. In less than a month, a single packing plant required 124 animal-disease investigations because market hogs started showing up with lesions and vesicles. The good news was the pigs tested negative for FADs; the bad news — they tested positive for SVV.

“There were zero reports of lesions at the originating pig sites, which involved five different states — Kansas, Minnesota, Iowa, Nebraska and South Dakota,” Schwartz told Pig Health Today. “So, either the pigs at the site were never infected or they were infected and the lesions healed relatively fast and we all missed it.”

There is much still to be learned about the virus — the transmission route, infectious period, risk factors, biosecurity effectiveness and more. But hog transport trailers are one suspected route of bringing SVV back to the farm. The linkage has been evident with market hogs as well as some sow-herd cases.

“We learned with the porcine epidemic diarrhea virus (PEDV) that it was not uncommon to have trailers arrive at the packing plant negative for PEDV. But when the trailer left the plant it was positive,” Schwartz said. “Then we drag the virus back to the farm.”

Although the exact steps to prevent SVV from entering a production site have not been scientifically confirmed, for now the best defense is to step up truck and trailer biosecurity protocols. This means wash, disinfect and dry the trailer between every hog transport.

“We don’t know if the thermos-assisted drying process is able to kill SVV, but we know it works quite well for PED and the porcine reproductive and respiratory syndrome virus,” he added. That essentially involves heating the trailer to a surface temperature of 150° F to 160° F for a period of time, say 30 minutes.

“As an industry, we talk about being prepared for an FAD; we talk about vaccine banks and many other strategies,” Schwartz said. “But part of that discussion needs to include how we manage our hog trailers in a way that would slow down or reduce the contamination risk in the event we did get an FAD in the US.”

 

Yeske: Multiple factors contributing to rising sow-mortality rates

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The spike in sow-mortality rates in recent years has everyone in the US pork industry searching for answers. Don’t expect any simple solutions, however.  In most cases, multiple factors lead to mortality or declines in sow performance, according to Paul Yeske, DVM, Swine Vet Center, St. Peter, Minnesota.

“Like many different things in the industry, it’s multi-factorial…not just one thing,” he told Pig Health Today.

Not all farms experience high mortality rates. Yeske said he sees a lot of variability among sow herds, and they try to understand why there’s a difference.

Expansion drives higher selection rates

One reason sow mortality increased relates to herd expansion. “As we’ve seen more expansion, we tend to have higher selection rates and sometimes end up with more mortality,” Yeske said.

“Ideally, we’d have a selection rate of 50% to 60%, and sometimes we end up…in the 70% to 80% range,” he explained. “Some of those animals probably shouldn’t have come to the barn to begin with.

“Make sure you bring enough of the animals in to allow for proper selection and not take what’s available,” he added.

In units with internal multiplication, Yeske recommended maintaining a purebred herd large enough to produce the needed replacement gilts. If gilts are outsourced, bring in enough animals for cover selection.

He also suggested making sure sow herds are sized properly. “Sometimes we just have to stand back and make sure the right animals come into the farm,” he said. “If the animal is structurally questionable, it’s going to be more difficult for that animal to stay in the herd.”

Lameness is a leading contributor to higher sow-mortality rates, along with prolapses. “Some research work is actively being done to try and understand what’s going on. We know it’s occurring; we just don’t know exactly why,” he added.

Maintain body condition

Another cause of sow mortality relates to higher production rates and body condition.

“We’re seeing higher levels of [sow] productivity than we’ve ever seen,” Yeske continued. “Are we meeting the needs of this higher-producing animal?” Research on sow diets dates back a number of years when production rates were lower, he noted.

Good body condition is essential for keeping sows in the herd. “If we get the animals into the herd, keep them in the right body condition,” Yeske said. “That’s going to add to their longevity.

“If the animals are yo-yoing a lot on weight, it’s going to add more stress and more challenges. Try to keep them very uniform and consistent on weight.”

Match health status

It’s important to remember that gilts entering a herd are stressed as they begin to develop herd immunity. Producers need to properly acclimate gilts to diseases they may face.

“Understand the health status of the animal coming in, manage it to match your herd and then identify the problems as they show up,” Yeske advised.

“If we don’t get that done right, that just adds more stress to those young-parity animals and ends up having them exit the system faster than they should.”

Fast intervention

Speed is also critical. “Herds that have fast intervention on problem animals tend to have the lowest mortality,” he said.

“Make sure you do individual pig care every day. Go out and check every animal every day. Make sure the animal is getting up and good on all four legs. Make sure the animal is eating and [there are] no other signs of any health problems,” he added.

 

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.

 

Practicing precision animal health

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Ross Kiehne, DVM, practices what he calls “precision animal health.”

“I’m only going to provide the vaccine or antibiotic that’s right for the pig at that time in its life to make it as healthy as possible,” the swine veterinarian says in a video produced as part of the Vets on Call series.

Growing up on the family farm, Kiehne says he witnessed the high level of livestock care shown by his father, who taught his son that the farmer is “the guardian of the welfare of the animals first and foremost.”

“We have to speak for them because they can’t speak for themselves,” stressed Kiehne, with the Swine Vet Center in St. Peter, Minn.  “I take that pretty seriously.”

Visiting a farrowing room, Kiehne focuses on the health and welfare of the sow and her recently born piglets.

“We want to find the right environment for them,” he says. “These sows have feed and water at all times; the sow is contained; it’s safe for the piglets to move around her all the time in a warm, dry environment.”

Even though he’s not in every swine barn every day, he can help the people who are by showing them what to look for and how to give the best care possible to the animals.

“Half of my job as a veterinarian is devoted to training the people who will take care of the pigs on a daily basis.”

And that involves treating sick animals. Kiehne says the welfare of the animal is much better if sick animals are treated with the proper antibiotic until they recover.

“We want everyone to understand where their pork comes from; this is how it’s made and we feel pretty good about it,” he says.

 

 

Vets on Call is a video series presented by Zoetis to showcase the important roles veterinarians play in food-animal production.

 

Yeske: Provide better pig care — one animal at a time

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Taking time to walk the pens, make eye contact with each pig and pull the sick ones for individual care seems to conflict with the basic tenets and efficiencies of population medicine.

“It is a big task, but we feel it’s a very important part of doing what’s right for the pig,” said Paul Yeske, DVM, Swine Vet Center, St. Peter, Minnesota.

“Individual pig care [means] to make sure we look at every pig every day — and that we evaluate them essentially from tail to snout — to try to identify any potential problems that pig may have as quickly as possible,” he told Pig Health Today.

Yeske says the approach involves three basic steps: Identifying the at-risk pig, being specific about its symptoms and effectively communicating the situation to others in the operation.

Practically speaking, he adds, that process begins with spotting the outlier — the pig that simply strikes you as somehow unusual.

“I encourage caretakers as they walk through the barn to develop a pattern as they go through each pen, to make sure they get an opportunity to look at every pig,” he said. “Basically, you’re looking for any of the clinical signs that the pig isn’t normal.”

For example:

  • Is he coughing?
  • Does he have diarrhea?
  • Is he gaunt and not eating?
  • Is there nasal discharge?
  • Does he appear stiff or lame when he moves?

Next, individual treatment protocols with an injectable antibiotic — typically already in place and specific for each farm and for each flow and system — can be called into use right away and used under veterinary supervision.

“Early intervention is really the key as we talk about individual pig care,” Yeske said. “We know that if we treat a pig later in the course of the disease, we have poorer response to treatment. If we can treat the pig earlier, we can have a better response.”

Research has proven that, particularly on farms with low health status, training caretakers to identify and treat sick pigs at an early stage of disease can improve growth and productivity during the all-important nursery and growing periods.1

“It does take time,” Yeske conceded, “but the payoff is very high. We get the pig back into production faster. The quicker we can identify that pig, the quicker we can get that pig treated and the better the response. The payback for the producer is very high because we get that early intervention ….  And we know it’s the right thing to do for the pig.”

1. Pineiro C, Morales J, Dereu A, et al. Individual Pig Care program improves productive performance and animal health in nursery-growing pigs. J Swine Health Prod. 2014;22(6):296–299.

Yeske: Mycoplasma elimination ‘always a good strategy’

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Eliminating mycoplasma from a herd works well with a fast payback, even in hog-dense areas, according to research conducted by Paul Yeske, DVM, Swine Vet Center, St. Peter, Minnesota.

Research indicates mycoplasma can travel 6.2 miles to infect an unrelated hog operation, called lateral transmission. Yeske wanted to see how frequently this occurred, especially in pig-dense areas. At the same time, he could check the success rate of mycoplasma-elimination efforts.

Yeske’s field study used five different hog production systems in southwest Minnesota, and northwest and northeast Iowa. The herds were validated mycoplasma-negative. Researchers followed pigs at 10 grow-finish sites from each of the five production systems. They carried the study through two marketing seasons, summer-fall and winter-spring.

At the end of the finishing period, researchers looked at serology of the pigs to see if they were exposed in the field to mycoplasma.

Lateral transmission rare

“Only 6% of the sites had become positive,” Yeske told Pig Health Today, following his presentation at the 2017 Leman Swine Conference.

“We learned (lateral transmission) does happen but at an infrequent rate. This was a true field study…with lots of hog barns in the area.” One farm in the study was located within 6.2 miles of 120 finishing units.

Why the low transmission rate? “It’s a slow-growing organism and difficult to transfer in that mechanism,” Yeske suggested.

Mycoplasma elimination pays

The low transmission rate also proved mycoplasma-elimination programs work. “This should help people feel more confident going into an elimination program that they will be able to return their investment,” he said.

“Also, our data shows if you are having mycoplasma problems, it’s probably your production system and not the neighborhood,” Yeske added. “You need to look at your sow-herd stabilization and identify how to do a better job with gilt introduction. Try not to send a high load of mycoplasma through the grow-finish population.”

Overall, he recommends mycoplasma elimination instead of living with the disease. “My belief is it is always a good strategy,” Yeske said. “But in certain instances, some production systems will make a choice to live with the disease.”