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Regional Methods for Controlling PRRS

by 5m Editor
18 June 2010, at 12:00am

Extensive scientific study and on-farm research is starting to pay off in the battle against porcine reproductive and respiratory syndrome (PRRS) virus, writes ThePigSite senior editor, Chris Harris.

An update on the findings of the research presented at the World Pork Expo in Des Moines, Iowa, this year showed that the protocols that have been put in place over the years in the battle against PRRS are showing dividends.

In the presentation, sponsored by Boehringer Ingelheim, Dr Scott Dee from the Swine Disease Eradication Center at the University of Minnesota, said the development of area regional control and elimination (ARC&E) programmes, along with increased understanding of aerosol transmission and developments in air filtration, biosecurity and refined herd diagnostic techniques have proven to be effective in reducing PRRS virus transmission.

He said that the discovery that the virus could be transmitted through the air had led to developments of filtration systems on pig houses and by using ropes for the pigs to chew on they had been able to monitor the disease within the houses and herds.

The methods they had devised including mapping the spread of the disease in specific areas had led to efficient use of vaccines to control the disease.

"In the last five to seven years, the swine industry has made major strides in understanding how PRRS virus spreads; what biosecurity protocols to use to prevent transmission; and how to more accurately diagnose and manage the disease when it occurs," Dr Dee said.

"One of the most recent developments is called area regional control and elimination, which takes a 'big picture' approach to disease control by calling for collaboration of producers and veterinarians.

"This process is based on understanding the PRRS status across farms, as well as the risk factors that promote virus spread, to improve disease control within an area or region."

He added: "The strategies for PRRS control are still working."

He said that the whole industry and the researchers need to work together in regional collaboration to ensure the disease is controlled.

The aim of the area regional control and elimination has been to eliminate PRRS on farms in low prevalence and low density areas for pigs. At the same time the programmes are attempting to control PRRS in the areas with a higher density population of pigs and hence a higher risk of the disease and a higher prevalence.

The major focus for the surveillance programme has been in Stevens Country in north east Minnesota.

The result of the surveillance and eradication programme has been to improve pig performance by reducing the wild-type virus load in the control areas and to reduce the risk in the long term of the viruses getting back into the PRRS elimination areas.

Currently, the ARC&E working model that is used for every region includes five phases of completion:

  • Feasibility assessment
  • Pig-related identification
  • Region characterisation
  • Design of PRRS elimination or control strategies
  • Execution and monitoring of farm-specific plan

"We are exploring the feasibility of implementing this approach in Minnesota and preliminary results are promising," Dr Dee added.

Dr Jean Paul Cano from Boehringer Ingelheim said that the current protocols for the regional programmes were both a feasible and repeatable process.

He said the aim was to get the farms to work together to prevent the disease spreading.

He said that working with individual farms would have limited success, because of the way the virus can spread - particularly through the air. However, working with groups of farms gives a greater success.

Both Dr Cano and Dr John Waddell from the Sutton Veterinary Clinic in Nebraska said that by using information gained from the Production Animal Disease Risk Assessment Programme (PADRAP) the researchers and vets have been able to successfully identify, benchmark and index those processes that are either effective or ineffective in preventing and controlling the spread of PRRS.

"Because the risk assessment data is so extensive and detailed, we have a high level of confidence in what protocols work, based on an operation's type of production flow, geography and concentration of production facilities in the area, disease status, vaccination methods, transportation equipment and other variables," said Dr Waddell.

"These types of models help us to manage not only PRRS virus, but also a number of other swine diseases that follow similar routes of transmission and infection."

Dr Waddell said that by using biosecurity precautions, they were able to minimise the risk of introducing infection and disease into the pig herd.

"Through biosecurity we are first closing the big holes, and then we start to close the smaller holes," he said.

"If we are in a pig dense area, hygiene is of the utmost importance."

He added: "Transmissible gastroenteritis and now PRRS are starting to be eliminated from the farms.

However, he warned that while obvious biosecurity measures are starting to reduce the risk of spread of the disease, farmers, vets and others in the industry have to be aware that disease can be spread in numerous other ways including poorly disinfected existing premises when restocking, transportation, farm personnel, needles, insects and aerosols.

However, live animal transmission, including through semen is the greatest risk for herd infection.

Among the measures that have been found to be successful are the use of filtration units to reduce the risk of spread of the virus through the air, diagnosis of the disease from fluid samples collected on ropes hung in the pig houses, sample testing, aerosol collection, improved ELISA tests and PCR tests and sequencing and an improve vaccination programme.

The area based programmes had been able to map the risk on specific farms in specific regions and through education and communication tools and better data management and analysis the teams had increased their control over the virus.

Dr Cano said that vaccination plays a critical role in most disease management protocols to reduce PRRS infections on the farms in the regional control programme areas.

"Research shows the use of vaccine has direct benefit when used to mitigate the clinical consequences of infection and improves the health and performance of pigs," he said.

"In addition, we've learned vaccinations have indirect benefits in reducing the level of virus and virus transmission within vaccinated populations."

Consequently, reducing the level of PRRS virus that can be transmitted within a facility impacts the dynamics of the entire swine production system.

"Depending on the type of production facility, PRRS status and other factors, immunising pigs against the virus, stabilising the herd or even reducing the level of virus transmitted may help producers achieve their goals," Dr Cano added.

"Mass vaccination intervention in area regional control programmes can be one of the complementary tools along with a herd closure strategy; gilt acclimation programmes; and appropriate pig flow and biosecurity protocols. Vaccine can provide protection and biologic and economic benefits when PRRS-naïve pigs are placed into high prevalence areas for finishing."

Dr Dee added that, thanks to advances in PRRS research and industry tools and processes, swine veterinarians and producers now have enough information to make a difference when it comes to controlling this devastating disease.

"The most effective and successful PRRS control and prevention within an area requires a high degree of cooperation, coordination and collaboration within and among production systems in a region," Dr Dee concluded.

"Fortunately, producers have a number of effective tools and processes available today to better help them determine current status, assess PRRS risk, measure and monitor infection status and improve their disease-management decision making."

Further Reading

- Find out more information on PRRS by clicking here.
June 2010