A new study shows that porcine reproductive and respiratory syndrome virus (PRRSV) can be detected and isolated from deep tracheal secretions antemortem. What does this mean for the pork industry?
“PRRSV is a highly infectious agent that results in economically significant disease in swine. Although there are numerous sensitive sample types for detection and isolation of PRRSV from swine, many require post-mortem collection,” explained Casondra Snow, a second-year student at the University of Minnesota College of Veterinary Medicine, during the Allen D. Leman Swine Conference.
Research has shown that the probability of acquiring a PRRSV viral isolate from a sample increases when the Ct value obtained from PCR is low, she added. Deep tracheal secretions are a sample type that is used to detect other respiratory pathogens, such as Mycoplasma hyopneumoniae. However, the ability to detect and isolate PRRSV on ante-mortem tracheal secretions has not previously been assessed.
Snow wanted to evaluate the feasibility to detect and isolate PRRSV from deep tracheal secretions as her project with Boehringer-Ingelheim Animal Health through Iowa State University’s Swine Veterinary Internship Program.
“When wanting to collect a sample for viral isolation of the PRRSV strain circulating in a herd, it is common to euthanize a pig with clinical signs of infection. We wanted to know if deep tracheal secretions would also be sensitive enough for viral isolation of PRRSV allowing for antemortem collection and eliminating the need for euthanasia,” Snow said.
As well, the swine production industry is moving in the direction where attempts for dual elimination of M. hyopneumoniae and PRRSV are becoming more popular, she said, meaning that sensitive sample types for these pathogens are becoming more necessary.
“Anticipating this need, we wanted to find a sample type that allows for collecting only one sample to detect both pathogens with high sensitivity while knowing the status of individual pigs,” Snow said.
How It Worked
For this study, Snow collected deep tracheal secretions from gilts at Country View Family Farms with rubber catheters at 14 and 28 days post-placement in the gilt development unit where they were naturally exposed to PRRSV. All of the samples were tested for PRRSV with PCR, and virus isolation and genomic sequencing were attempted on the samples with the lowest Ct value from PCR.
Snow discovered that 99% of the deep tracheal secretion samples were positive for PRRSV on PCR, and her team successfully achieved virus isolation and genomic sequencing on all of the samples attempted.
“This research has shown the potential of using deep tracheal secretions to collect fewer sample types reducing overall animal handling time when collecting samples for both M. hyopneumoniae and PRRSV. This sample type would be especially useful for application in dual M. hyopneumoniae and PRRSV control and elimination programs,” Snow said. “This sample type has also proven to be useful for virus isolation without euthanasia.”
Snow was one of seven students competing for the 2024 Morrison Swine Innovator Prize.
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