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The Latest on Swine Disease Research

As pork producers head into winter, herd health is top of mind. There is a growing list of emerging and reemerging diseases, including porcine epidemic diarrhea virus (PEDv) and porcine reproductive and respiratory syndrome (PRRS). To keep producers up-to-date, here are highlights from the Iowa State University James McKean Swine Disease Conference, held November 5-6, 2015.

New Tool for Monitoring the Health Status of Swine Herds
Managing, monitoring, and maintaining the health status of U.S. swine has become increasingly complex. A new Web-based database application has been developed at Iowa State University that uploads farm-site information and receives diagnostic results. This tool, called the Secure Animal Health Diagnostic Database, allows users to monitor the health status of farms and movement of pathogens within a region in near real-time. The pilot project will be rolled out in 2016 to participating veterinarians. 

PRRSv Challenges
PRRS is one of the most economically important swine diseases worldwide, costing the U.S. swine industry about $664 per year due to reproduction losses and decreased pig performance. The PRRS virus mutates rapidly, making it a moving target for vaccine development. Vaccines don’t prevent shedding of the virus, and even vaccinated herds can have “silent” PRRS, says Daniel Linhares, College of Veterinary Medicine at Iowa State. All producers need to keep biosecurity strict, even when it seems the virus is not present. Don’t trust your eyes to know if PRRS is affecting your herd, says Linhares. You must test for the virus. Pig genetics companies are breeding animals now that are more resistant to the PRRS virus. Those pigs should be available in the next five years, he says.

For the latest news of PRRS research around the world, go to http://field-prrs.blogspot.com/.

Reducing the Impact of Mycoplasma Hyopneumoniae
Mycoplasma hyopneumoniae is a common cause of late-finishing respiratory disease in pigs. Antibiotics work short-term to control the bacteria, but do not stop colonization, says Shamus Brown, a veterinarian with Iowa Select Farms. Antibiotics are not cost-effective or economically sustainable long-term, he says. Instead, Iowa Select is in the early stages of testing exposure to gilts at a young age to M. hyopneumoniae. The premise is if gilts are infected early, there will be colonization, clinical signs, an immune response, and shedding. By the time they enter the sow farm, they will have a robust immune response to any exposure there. A small trial is also looking at purposeful exposure in the nursery. The results of these trials will help determine if purposeful exposure is a viable option to improve pig health due to M. hyopneumoniae.

FDA Guidance on Judicious Use of Antibiotics
The new Veterinary Feed Directive (VFD) rule requires all therapeutic uses of antimicrobials in feed and water to be under veterinary order or prescription. The new rule impacts farms of all sizes and imposes a burden on farms and veterinarians, says Liz Wagstrom, veterinarian with the National Pork Producers Council. “During the transition period, there will be many situations and scenarios that will need to be clarified to allow the veterinarian, feed mill, and producer to properly comply with the rule,” says Wagstrom.

For more information on the VFD rule, go to: http://www.fda.gov/AnimalVeterinary/DevelopmentApprovalProcess/ucm449019.htm

3 Things the Pork Industry Learned from the PED Outbreak
The experience the U.S. pork industry is having with PED provides many lessons, says Paul Sundberg, veterinarian with the Swine Health Information Center. Here are three:

1. The likelihood of identifying the pathway of introduction for production diseases, vs. classical foreign diseases like foot-and-mouth, is extremely small given the inputs the industry gets through foreign trade. There will be more foreign production diseases that will enter the U.S.

2. The U.S. pork industry can’t expect the USDA to protect our herds from these risks. The resources are simply not available. The industry needs to take a more active role responding to emerging, non-regulatory production diseases. With PED, time was wasted. Producer willingness to share disease status helps inform veterinarians, other producers, and the industry. The health of pigs on every farm can benefit.

3. Better state-federal-industry coordination is essential. Pork producers taking responsibility and working with health officials will mean a coordinated response to emerging diseases. 

For more information, go to http://swinehealth.org/.

How Antibiotic Regulations Could Affect Herd Health
Strict antibiotic regulations have been imposed on Danish pig production over the past 20 years. Here is a look at how herd health, productivity, and animal welfare has been affected.

In 1995, a law took away Danish veterinarians’ right to sell antibiotics and vaccines. The goal was to take the economic incentive away from vets. The law did not result in decreased use of antibiotics, says JMJ Agerley, veterinarian partner in SvineVet, Haderslev, Denmark.

In 1998, antimicrobial growth promoters in feed were banned in finishers. In 2000, they were banned in weaners. This cut antibiotic consumption in half in three years.

In 2000, a national database called Vetstat was built. It tracks all veterinarian prescriptions per farm and numbers of animals on the farm.

From 2000 to 2010, total antibiotic consumption in the pig industry increased linearly with the increase in pig numbers. There was no increased antibiotic use per animal, says Agerley. “The Danish media, though, had big headlines of antibiotic consumption increasing.”

In 2010, a yellow card system was implemented by law. It imposed maximum doses of antibiotics allowed for each type of pig. If use was too high, the farm and its veterinarians were sanctioned. In 2010, 25% of all pig farms in Denmark got a warning that they had passed the yellow card line and had nine months to change the situation. Journalists were granted full access to Vetstat and published the names and addresses of all the “yellow card” farmers and veterinarians, who felt stigmatized. It turned out that the Vetstat database was full of errors, says Agerley.

Implementation of the yellow card and publish access to the Vetstat database resulted in a 25% decrease in antibiotic use in pig farms from 2010 to 2011. During 1010, mortality in weaners increased by 25% and daily weight gain decreased. The prevalence of abscesses in finisher herds increased by 50%. Farmers were not treating diseases in fear of the yellow card and being hung out in the media and by their neighbors, says Agerley.

By 2012, the situation on farms normalized as farmers got used to the yellow card system. “We now use smaller doses and treat illnesses for a shorter period of time,” says Agerley. “Vaccines are used more, including vaccines that are not cost effective. We are working much more with feeding, hygiene, and management.”Veterinarians good at managing high productivity with a low use of antibiotics have increased their client base, he says.

New legislation is aiming for a 15% reduction in antibiotic use over the next three years. Farms must have extremely good management to ensure good productivity, says Agerley.

PED Virus on Swine Trailers
In spring 2013, PED was detected in swine for the first time in the U.S. and spread quickly across much of the country, partly due to contaminated livestock trailers. A study by Iowa State University and AMVC Management Services in Audubon, Iowa, found that PED virus in the presence of feces on metal surfaces under freezing conditions can be inactivated by applying a 1:16 or 1:32 concentration of accelerated hydrogen peroxide disinfectant in a 10% propylene glycol solution for at least 40 minutes.

Euthanasia Update for Pigs
The pork industry is in a challenging position regarding euthanasia. Blunt force trauma, an effective and reliable method used for decades, can be disturbing to the public. Many pork producers feel pressure to move away from this practice, says Kate Dion, veterinarian with The Hanor Company, Spring Green, Wisconsin.

One alternative is using non-penetrating captive bolt gun devices. These exist in the market and range from single shot devices to pneumatic devices powered by compressed air or carbon dioxide. The effectiveness in research studies nears 100%.

Currently, these bolt guns are only recommended for pigs up to 12 pounds. They may be effective as a single-step euthanasia method for heavier pigs, says Dion, but more research is needed. The goal is to have one type of euthanasia device for farrowing through nurseries.

Mechanical devices need maintenance and cleaning. They are often used for sick animals, so can spread disease if not cleaned and disinfected properly.

During times of disease outbreak or disasters, when mass euthanasia is necessary, most farms will not have enough bolt guns on hand for timely euthanasia of large numbers of pigs, says Dion. Furthermore, some models of guns are heavy and cause user fatigue.

Removing blunt force trauma from a farm’s euthanasia plan requires more than just purchasing a device, says Dion. Continual on-farm training is necessary. Bolt guns add expense and may not be practical for every producer in all situations. “As an industry, we must continue to investigate euthanasia techniques that are safe, effective, reliable, practical, and economical for on-farm use,” says Dion.

Identifying The Virus Causing Porcine Congenital Tremors
Congenital tremors (CT) is a disease in newborn pigs characterized by repetitive contractions of skeletal muscle. The tremors cease when piglets are at rest. The disease was first described in the U.S. in 1922.

Using next-generation sequencing, Iowa State University detected a virus in tissue samples from piglets with CT. The viral RNA was not in samples from nonaffected pigs. Following inoculation of the novel virus, 75% of piglets farrowed had tremors. The virus was detected in samples from affected piglets.

Now that the CT virus has been detected, epidemiologic studies are needed, says Iowa State University.

PRRS Investigations Show 3 Main Risk Factors
From January 2015 to August 2015, eight PRRS outbreaks on breed-to-wean farms in Iowa were investigated by the Center for Food Security and Public Health, Swine Medicine Education Center, and Iowa State University College of Veterinary Medicine, all based in Ames.

The events determined to have the highest risk among the eight outbreaks were:

  • Movement of cull sows
  • Employee or repair personnel movement
  • Feed delivery

Vehicles used to haul cull sows had been used to haul replacement gilts with unknown disinfection procedures. Part-time sow farm employees worked at other sites in different stages of production and did not always practice downtime away from other swine. Feed mill equipment was shared with compost equipment in three outbreaks, and feed mill biosecurity practices were highly variable.

Case Study of Senecavirus A in Finishing Pigs
Senecavirus A (also known as Seneca Valley virus or SVV) hit herds in the U.S. beginning in July 2015. SVV has been seen in farrowing operations, finishing pigs, and pigs on the show circuit.

The Orange City Veterinary Clinic, Orange City, Iowa, got a call on July 28 from a field manager regarding extensive lameness in market-weight hogs in a 1,200-head wean-to-finish barn in South Dakota. The pigs were crossbred white hogs that originated from Canada. “When the pigs were made to stand and walk they would shake, squeal, and try not to move,” says veterinarian AJ Smit. The field manager estimated that 50% of the herd was showing some degree of lameness.

Examination of the feet revealed blanched white, raised vesicular lesions, separation of tissue of the hoof wall and declaws, partial sloughing, and ulcerative lesions. Nasal vesicles and oral ulcerations were also observed in 25% of the herd.

Given the severity of the lesions and possibility of foot and mouth disease (FMD), the state veterinarian of South Dakota was notified and a foreign animal disease investigation was initiated. Samples were sent to the Plum Island Animal Disease Center and tested for FMD, swine vesicular disease, vesicular stomatitis virus, and vesicular exanthema of swine. All were negative. Further tests were positive for SVV.

The feet lesions were treated with Oral-Pro Sodium Salicylate 48% for five days. Morality was minimal.

“Marketing pigs with vesicular lesions is problematic and good communication is essential,” says Smit. First, all testing and diagnosis must be made. Second, pigs should be held from market channels until acute lesions are no longer present and lameness subsides. (It took more than two weeks for this to occur in this case.) Packers and inspectors were contacted and told the pigs were diagnosed with SVV, but the lesions had healed and were not evident on pigs coming to the slaughter plant.

It is paramount that lesions are identified prior to marketing and that proper communication, diagnostics, and documentation occur. Packers and inspectors recommend a written notification and laboratory report. If pigs have lesions at the slaughter plant without prior communication to the inspector, a delay in processing and economic losses can result.

Clean-up efforts at the farm were performed using a double disinfection program of both barn and trailers used to transport the pigs. The office and all tools used in the swine barn were thoroughly cleaned. Open treatment bottles were discarded. After environmental samples from the farm still tested positive for SVV, a third disinfection was performed using 3% bleach solution. All new pigs in the barn are tested for SVV.

An outbreak investigation was performed by Iowa State University to identify risk factors for entry of SVV into the site. The investigation revealed a high risk associated with trucking biosecurity when the first loads of market hogs were removed from the barn. The trucks used were used to haul other pigs from different sources. People movement was also a high risk for disease transmission. Employees and visitors, such as the load-out crew, were not required to have downtime before entry in the facility.

Given the similarity in clinical signs to foot and mouth disease, it is imperative that producers and veterinarians identify and not dismiss these lesions, says Smit. A foreign animal disease investigation must be performed on all cases of vesicular lesions. “Complacency is the biggest threat to allowing a foreign animal disease to enter our production systems,” he says.

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