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Previously, the virus could be detected only in acute cases while it was still reproducing and infecting a host pig. In such cases, the virus could be identified through the use of a test known as a polymerase chain reaction 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, whether it’s shedding the virus or not. It’s the first test available to the U.S. veterinary community that can detect PEDV antibodies.
“The new test gives practitioners and their clients a historical perspective,” said Dr. John Johnson, 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 polymerase chain reaction results, will provide additional crucial information as veterinarians and their clientele assess the risk of moving a group of animals into a PEDV-negative population.”
Dr. Kyoung-Jin Yoon, 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 PEDV antibodies in a blood sample. If the antibodies are present, then the pig in question has been exposed to the virus before, Yoon said.
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 said. “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 said. 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 Porcine Epidemic Diarrhea Virus in early May. Since then, the diagnostic laboratory has helped to confirm cases of the disease in 17 states, including Iowa, Yoon said.
The virus was first diagnosed in 1971 in Britain, and Europe has experienced sporadic outbreaks in the years since, while the disease has become prevalent among pigs in Asia since 1982. PEDV 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 said.
He said discovery of the disease in the United States has led a wide range of personnel in the ISU College of Veterinary Medicine to collaborate to help Iowa producers deal with the disease.
“This is a new disease to the U.S., and when that happens, we have to either develop new tests or try to find what’s available from other parts of the world,” he said. “When those things happen, we have to have a lot of people help out. In this instance, we’ve seen great collaboration between faculty, technical staff and graduate students at Iowa State to help with our response to this virus.”
September 13, 2013 - ISU
