Cover Story: Winning those small victories in the ongoing battle against PRRS
Wednesday, February 4, 2009
Eradicating PRRS completely seems like an impossible task, but it doesn't have to be accomplished all at once. 'If you can bite it into little chunks,' says one operator, 'it becomes manageable.'
by KATE PROCTER
After years of dealing with the disease, receiving a positive test result for Porcine Reproductive and Respiratory Syndrome (PRRS) is not the kiss of death it once was. Several simple strategies exist that can make the virus easier to manage, while helping to reduce the risk for herds across Ontario.
Those strategies include vaccination, McRebel, Danish Entry, employee management, communication with neighbours, focus on secondary infection control, and rodent control. Even thinking about barn location can be considered a disease reduction and control strategy.
In late November, 2007, one of the 1,220-head Synergy System sow barns that Clancy Annesley oversees north of Paisley tested positive for PRRS. The symptoms were atypical in that the sows were not affected reproductively. The rate of abortions did not change, nor did the number of stillbirths and mummified piglets.
However, the piglet quality at weaning was poor and the herd had a higher than normal mortality rate, especially among piglets that were 10 to 16 days old. The pigs in the nursery were also exhibiting higher than normal mortality rates.
The herd had been routinely vaccinated against PRRS before diagnosis with a commercial vaccine and gilts were isolated and blood tested before entering the herd.
Upon receiving the positive diagnosis, Annesley says that he adopted a strict McRebel policy in the farrowing rooms and vaccinated all the sows in the herd again with the commercial vaccine.
McRebel is a 10-point protocol that is conducted in the farrowing room. One protocol restricts cross-fostering to the first 24 hours of life and keeps all fostering within the same room. Nurse sows for small pigs are not used. Fostering is greatly reduced, needles are changed between litters and also between sows, and there is no fostering between rooms. Annesley says his staff also was more careful to euthanize small, weak piglets early. "McRebel was a big reason that we eliminated problems," says Annesley.
Once the piglets were consistently testing negative for PRRS, the focus changed to the three 2,500 head nurseries. Since the nurseries were all on the same site, all of them were emptied before refilling.
Before the PRRS outbreak, the prewean mortality (PWM) in the herd was eight to 10 per cent. For four months during the outbreak, PWM was 18 to 20 per cent and it is now running at about 10 to 12 per cent, reports Annesley. While this is still slightly higher than it was before the break, he suggests that the weaker pigs are not going to the nursery at all and the quality of pigs going in and out is higher.
Mortality back to normal
The mortality rate in the nursery before the outbreak was 2.5 per cent, during the outbreak was six to eight per cent and is now back to between two and three per cent. The piglets leaving the nursery are now three to four kilograms heavier than piglets of the same age had been before the outbreak and consistently reach 30 kilograms in seven weeks Annesley says that he has kept using some of the McRebel protocols. For example, he has not used any nurse sows since the break and piglets are not moved after 24 hours of life. "You have to pay really close attention to the sizing of the pigs at that time," he says. He generally tries to keep piglets with their litter mates, but will foster them in order to make the litter size and piglet size within the litters more even.
"McRebel has shown us the value of a resident litter on a resident sow," says Ryan Martin, production manager in a 2,000-sow system near Arthur. He had a positive PRRS test result in an 850-head sow herd in September 2007. He inoculated all the sows two weeks later and was producing 100 per cent PRRS-negative piglets by March, 2008.
Martin uses a similar McRebel protocol, except he did not sort the litter based on the size of piglets. One of the challenges he faced was achieving a commitment from everyone to persevere with McRebel. "We were not going to give up, we were not going to slow down on McRebel until everything was 100 per cent PRRS-negative," he says.
McRebel has been an ongoing success and his staff has seen the value in using it whether the virus is there or not. Before the PRRS break, they were weaning 26.1 pigs per sow per year (P/S/Y) with an 8.7 per cent PWM. During the break, P/S/Y dropped to 22.6 with a PWM of 14.5 per cent. In the eight months following the break, they were weaning 26.5 P/S/Y with a PWM of 11. 4 per cent. Their mortality rate in the nursery is typically around one per cent and hit 4.7 per cent during the worst part of the PRRS break. "We are now experiencing unprecedented production," says Martin.
Because they mix pigs from different sow units in the nursery, his team had to focus on reducing the viral load to which the pigs were exposed. "We stopped agonizing over mixing pigs," he says, instead looking at ways to keep infection to a minimum. They euthanized sick piglets early and tried to reduce nose-to-nose contact between the pigs. "We started looking at the room through microscopic eyes," he says.
His staff also focused on fighting secondary infections in the nursery. They started vaccinating against circovirus and medicating for other ailments. They gave the animals aspirin when necessary to help them feel better and keep eating, which in turn helped them fight infection.
One of the other vital keys to beating PRRS in this herd was psychological, explains Martin. Learning that PRRS could be spread by aerosol transmission was important because it stopped people from blaming each other for bringing the disease into the barn. "There was a mental relief to be exposed to Scott Dee's work proving aerosol transmission is possible," says Martin. (Dr. Scott Dee, a world-renowned PRRS researcher, is the director of the Swine Disease Eradication Center, University of Minnesota, and regularly speaks to Ontario producers about his latest findings.)
Because there were so many sick animals, Martin says that his staff also had to battle the hopelessness that seems to enter the barn with the virus. "There was a tendency to want to throw up your hands and walk away," he says. "Managers have to get in there and help with the fight," he stresses.
'PRRS-free' zone
Brent Robinson, from Vista Villa Genetics in Huron County near Seaforth, is looking at a slightly bigger picture. The Robinsons have battled PRRS throughout their system, which is now 100 per cent negative. Once they had that in hand, Robinson says he started thinking about creating a "PRRS-free zone," just within their local neighbourhood.
"It is really in the initial stages," he says of his proactive approach. Robinson talked to several of his pork-producing neighbours and is happy to report that everyone was really open to working together. "It is kind of a refreshing thing," he says. "Five years ago, people never thought that we could get rid of PRRS, but the mindset is changing."
Completing a PRRS Risk Assessment made Robinson think about who was producing pork in his local area. In order to complete the assessment, the Robinsons drove the roads to find the farms within certain target areas of the assessment. They found three main pig farms within the closest range identified.
Robinson decided to start small and approached those producers who were located the closest to Vista Villa at the end of November, 2008. "We thought we had better start small and build on it," he notes. Robinson says he was surprised at how open people were to blood-testing their animals and sharing the results. "I'll keep you informed if you don't mind keeping me informed," was his approach.
Eradicating PRRS completely seems like an impossible task, but Robinson points out that it doesn't have to be accomplished all at once. "If you can bite it into little chunks, it becomes manageable," he says. Being open to learning from setbacks and keeping going forward are also key parts of the puzzle.
Vista Villa is paying for their neighbours to blood-test the pigs. Some people do not see the need to test if they are not experiencing clinical signs in the barn. However, Robinson feels strongly that it is important to know the health status of the animals. "Even if you just start with testing once per year and go from there, knowledge is power," he says.
Robinson says that one of his neighbours was even willing to place pigs in a different nursery if they did happen to test positive, so they would not be going into an area where there were already lots of pigs.
Robinson explains that when one of his nurseries tested positive for PRRS, he found an isolated barn away from other pigs to put that group. "We took them out of pig-dense Huron and Perth Counties so they didn't affect anyone else," he says. By putting a barn full of virus-shedding pigs in the middle of a pig-dense area, a huge number of pigs can be affected, he adds. "It is important to think not only about our own little group, but also how to protect others."
Danish Entry works well
One of the other simple steps Vista Villa has taken is to install Danish entries in all of their barns. "Some are pretty simple. They have really helped us at a cost of between $100 and $200 per entrance," Robinson says.
The Vista Villa entries do not all have sinks, as the standard Danish Entry System does. In the cases where it was impractical to install a sink, use of a hand sanitizer is recommended as an option. And a barrier is created between outside clothes and inside. When workers enter the barn, they sit on a bench, remove their outside shoes, switch to the other side of the bench to put on the inside boots and never cross-contaminate the area.
The Danish Entry System has also worked well for Bert Prinzen, who has a 1,000-sow, farrow-to-finish operation near Port Dover. The combination of careful adherence to the Danish entry principle with a location in a low pig-dense area of Ontario has resulted in his operation remaining PRRS free. Prinzen's closest pork-producing neighbours are five miles away and maintain stringent controls in their operation.
He contracts half of his finishing, has a 3,500-head nursery and a 1,500 head finishing barn about one mile away from his sow barn. Prinzen has one person working in the finishing barn, one working in the nursery and two working in the sow barn. Every day, they meet for coffee at the sow barn. "We don't want to be locked in a barn and thinking we can't go out without showering," he says. "It is just a matter of changing shoes and washing hands."
Prinzen has had this policy in place since 1992, when he repopulated his herd, and has never had a shower-in policy on his operation. "We just do not want to be showering 10 times a day," he says. "It works for us, but I'm not going to say it would work for everybody, especially in areas like Perth County," Prinzen says.
Workers are very careful about the biosecurity on the truck they use to move pigs. They have a wash bay where the truck is washed, disinfected and dried between loads. They also keep tools such as welders and pressure washers separate in each barn.
A great rodent control program is another key part of Prinzen's operation. Every fall, he baits the attics of the barns. He also uses gravel around the outside of the barns and Roundup for weed control. "A good clean farm is the best defense there is," he says. "That and being lucky not to have a pig farm right next door." BP
McREBEL 10-point Protocol
Management Changes to Reduce Exposure to Bacteria to Eliminate Losses
• Only cross-foster within the first 24 hours of life to equalize litter numbers.
• Stop cross-fostering between litters for resizing or saving sick pigs.
• Do not move sows or piglets between farrowing rooms.
• Stop use of nurse sows for low viability pigs and runts.
• Immediately destroy piglets that become very sick.
• Minimize handling of piglets, especially for routine treatments.
• Do not move lightweight pigs backward to younger rooms or nurse sows.
• Immediately discontinue transfer of all material from farrowing rooms to other rooms.
• Use new needles between every litter and between every sow.
• Practice strict farrowing room hygiene.