Diagnostic tests key to helping swine producers fight porcine epidemic diarrhea virus

One week after the diagnostic lab at Iowa State confirmed that porcine epidemic diarrhea virus had spread to the United States, Animal Disease Research and Diagnostic Lab researchers at South Dakota State University released a diagnostic test to differentiate PEDv genetic material from that of other viruses, according to Jane Christopher-Hennings, ADRDL director and SDSU Veterinary and Biomedical Sciences Department Head.

With the first-generation, gel-based polymerase chain reaction (PCR) test online, the lab's molecular diagnostics group improved the test's sensitivity and cut the testing time in half, making it possible to get same-day results, explained ADRDL researcher Eric Nelson, a veterinary and biomedical sciences professor. The second-generation test was commercially available within a few months.

Diagnosing outbreaks quickly

ADRDL's quick turnaround time for diagnostic testing provides a real value to producers in South Dakota and the region, explained Glenn Muller, executive director of the South Dakota Pork Producers. "The diagnostic lab is the primary source of determining a true, confirmed case of PEDv."

The PCR-based test can also be used on environmental samples to detect whether items brought onto the farm are contaminated, Hennings explained.

In addition, the test results fulfill the U.S. Department of Agriculture reporting mandate, which also requires producers whose herds test positive to review their biosecurity measures with their veterinarians to pinpoint any changes that may be necessary.

Detecting antibodies

Once an animal is exposed to the virus, it develops antibodies, Nelson explained. ADRDL scientists produced several tests to detect the animal's immune response to PEDv. These tests are important, not only to identify animals previously exposed to PEDv but also to evaluate an animal's antibody response to vaccines, according to research associate Travis Clement.

Neutralizing antibodies, in particular, are important indicators of protective immunity to the virus, Clement explained. If pigs with these antibodies have negative PCR results, meaning they have stopped shedding the virus, they might be safely integrated into the operation.

Within four to six months, ADRDL had developed monoclonal antibody reagents used to detect PEDv in tissues from infected animals and to detect viable virus in cell cultures. Though ADRDL does vaccine research, Nelson said, "We've had our hands full on the diagnostic side."

ADRDL does antibody testing on candidate vaccines to determine whether the antibody levels measured are high enough to provide clinical protection against the virus and therefore predict their effectiveness, according to Hennings. ADRDL monoclonal antibodies became commercially available this spring and are used in multiple research laboratories developing vaccines.

"With an emerging disease, research, diagnostics and control measures are critical in limiting the damage and extent of the disease," added Hennings. Networking among diagnostic labs, especially in the Midwest with regard to swine diseases, helps researchers quickly identify new diseases and develop diagnostic tools.