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Routes of transmission
Still, big questions continued to plague researchers. How did PRRSV get here? Where did it come from? How is the virus transmitted? Understanding the routes of transmission was a big question, Philips says.
“Early on, I think about Scott Dee and his colleagues. They did an incredible amount of work – lots of push-ups and sit-ups – to identify the routes of transmission for this virus,” Philips says.
In addition to pig-to-pig contact, researchers learned PRRSV could be transmitted via semen to a breeding herd. Dee and his graduate students, Satoshi Otake DVM, and Andrea Pitkin, DVM, also discovered the virus could be transmitted by fomites, through contaminated transport vehicles, trucks and trailers. They also discovered it could be transmitted by aerosol over relatively short distances.
“Once the routes of transmission were identified, we could develop biosecurity protocols to mitigate those transmission risks and events,” Philips says. “That really ramped up our biosecurity protocols and procedures.”
Meanwhile, Montserrat Torremorell, DVM and now a professor in the Department of Veterinary Population Medicine at the University of Minnesota, was studying how to eliminate PRRSV from the herd while working for PIC. At the time, Torremorell’s research on letting the virus burn out in the sow farm and actually cleaning up farms on a large scale paralleled Dee’s research at the University of Minnesota.
“While she was cleaning [farms] up with her team, I was trying to keep negative farms clean. We were studying the routes of transmission,” Dee says. “Until we could understand how the disease was getting in, we were working with blinders on.”
Discovering a vaccine
Finding a vaccine for PRRS was a pivotal point in the pork industry, Dee says.
“The Boehringer Ingelheim vaccine was the first PRRS vaccine,” he adds. “Having efficacious vaccines that could provide partial protection could reduce shedding and spreading of the virus.”
The industry learned a lot during that time about how vaccines needed to be used because of PRRS, Torremorell says. Producers realized vaccines couldn’t be used alone without adjustments in the system.
“I think there’s a role for vaccines in the control of PRRS virus, but I don’t think you can use the vaccine and just forget about PRRS,” Torremorell says. “The vaccine is a tool, as a part of a whole package of biosecurity measures. The vaccine gives you some predictability, some consistency and some immunity so if the pigs get infected later, they can respond to the disease better with less economic losses.”
PRRS is a complex disease. No single person, or single way of doing things will be able to correct the disease, she says. Viruses, including PRRS, are constantly changing.
“So what you thought was working a year ago, may not be working now,” Torremorell says. “That’s why communication and collaboration between the different parties observing the disease are so important.”
Stay tuned for more! This is the first story of a three-part series on PRRS.
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