A research team from the University of Missouri and Kansas State University has been working to find a cure for porcine reproductive and respiratory syndrome virus (PRRSv), and their latest study disproved one way the virus is thought to spread.
"Initially, scientists believed that PRRSv bound to a specific molecule, known as CD169, and infected white blood cells in the lungs," said Randall Prather, distinguished professor of reproductive biotechnology in the University of Missouri College of Agriculture, Food & Natural Resources. "In our study, we've found that this is probably not how the virus is infecting pigs."
In the study, Prather genetically modified a litter of pigs so they would not generate the CD169 molecule, the theory being that the virus would have nothing to bind to and would be killed by the pigs' natural immune systems. However, after an initial test, the genetically modified pigs did become infected with PRRSv, negating the initial theory.
"While we didn't find what we were looking for, we did uncover important information about the infection," Prather said. "This information will help us narrow our search as we continue to fight this virus. We'll keep searching for answers until we determine how to stop PRRSv."
When pigs are infected with the disease, farmers must clean everything, Prather said. That means culling the herd, cleaning the barns and letting the pens sit empty until all viral material is killed. If that doesn't happen, PRRSv can continue infecting new groups of hogs.
Farmers have had access to vaccines for the last two decades, but experts warn that vaccines are not the best tool to fight the disease.
"Vaccines have been shown to lessen the impact of the disease on farms, but they are not a good tool to control or eradicate the virus," said Raymond "Bob" Rowland, co-author of the study and professor of virology at the Kansas State University College of Veterinary Medicine. "With this new information, we understand more about the mechanisms of this virus and how it acts once inside the pig's body."
The study, "An Intact Sialoadhesin (Sn/SIGLECI/CD169) Is Not Required for Attachment/Internalization of the Porcine Reproductive Respiratory Syndrome Virus (PRRSV)," was recently published in the Journal of Virology.