Iowa State University’s (ISU) development of a new diagnostic test for porcine epidemic diarrhea (PED) virus, a costly disease discovered for the first time in the United States this spring, will provide a crucial tool in early detection of the virus.
Previously, the virus could be detected only in acute cases while it was still reproducing and infecting a host pig using a test known as a polymerase chain reaction (PCR) assay. But those tests could give a false negative if the pig had stopped shedding the disease or if shedding had become intermittent.
The new test, called an immunofluorescence antibody or indirect fluorescent antibody assay and conducted using blood samples from pigs, will allow veterinarians and producers to know if a pig has ever had the disease in the past and whether it’s shedding the virus or not. It’s the first test that can detect PED virus antibodies.
“The new test gives practitioners and their clients a historical perspective,” says John Johnson, DVM, a clinician in veterinary diagnostic and production animal medicine. “It’ll help them to understand if a particular animal has been exposed to the virus before. This tool, coupled with PCR results, will provide additional crucial information as veterinarians and their clientele assess the risk of moving a group of animals into a PED virus-negative population.”
Kyoung-Jin Yoon, DVM, a professor of veterinary diagnostic and production animal medicine, led the effort in developing the new test. The screening works by detecting the presence of PED virus antibodies in a blood sample. If the antibodies are present, then the pig in question has been exposed to the virus before, Yoon says.
The screening, available through the ISU Veterinary Diagnostic Laboratory, costs $5.50 per sample and can be requested by local veterinarians.
“In order for this test to function, we must first have an isolated virus on hand,” Yoon says. “For a long time, it’s been difficult to isolate the virus in a cell culture, so there are a lot of tricks and manipulation we have to do to make this virus propagate in cell culture.”
The test will be especially helpful to pork producers who are looking for replacement breeding stock, Johnson says. By performing the test, producers can know if an animal has been exposed to the virus in the past before they bring it onto their farms.
The Iowa State University Veterinary Diagnostic Laboratory identified the first U.S. cases of PED virus in early May. Since then, the diagnostic laboratory has helped to confirm cases of the disease in 17 states, including Iowa, Yoon says.
PED virus infects only pigs and does not pose a threat to human health.
The primary symptom of the disease, which is spread through fecal matter, is severe diarrhea in pigs of all ages with high mortality in neonatal piglets. The most common sources of infectious feces are infected pigs, contaminated trucks, boots and clothing, making biosecurity measures on farms especially important to contain the spread of the disease. Hog producers who notice severe diarrhea among their herd should contact a veterinarian immediately.
Diagnosticians and clinicians in the ISU Department of Veterinary Diagnostic and Production Animal Medicine and the Iowa Pork Industry Center are now working closely with producers and veterinarians to implement best practices to diagnose the disease in other herds and to minimize its impact and prevent its spread to uninfected herds, Yoon says.
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