South Dakota swine producers and veterinarians have been closely monitoring the developments surrounding Porcine Epidemic Diarrhea (PED) virus infections over the past several months. In early May 2013, the industry was informed that this virus had been detected in swine herds in Iowa and Indiana. Since those first reports, as of Oct. 26, 2013, PED infections have been detected in 924 case submissions from 18 different states, said Russ Daly, SDSU Extension Veterinarian.
"The PED virus has been detected in one grow-finish site in late May in South Dakota, with an additional environmental sample found positive in August. Detection of PED in U.S. swine herds is remarkable, since the virus has not previously been recognized in our country, despite its long history in Europe and Asia," Daly said.
SDSU Develops helpful PED Diagnostic Test
At South Dakota State University's Animal Disease Research and Diagnostic Laboratory, a diagnostic test was developed and made available to veterinarians within a couple weeks of the virus's first detection. Initially, a gel-based polymerase chain reaction (PCR) test was developed; following that, a "real time" PCR test was perfected at SDSU as well.
"These tests can accurately differentiate PED virus from other similar viruses, and can detect the virus in very small numbers," Daly said.
The preferred sample for the test is manure from affected pigs or intestines from pigs that have died. The main reason for having diagnostics performed is to differentiate disease due to PED from disease caused by similar viruses such as Transmissible Gastroenteritis (TGE) virus. Some herds may wish to monitor their buildings or vehicles for the presence of PED virus; environmental samples may be submitted for that purpose.
After the first outbreak of PED, a pointed effort quickly took place, and is ongoing, among veterinary diagnostic labs to perform further research on PED, including the development of additional diagnostic tests such as blood tests that would detect antibodies, therefore previous exposure, to the virus.
"SDSU researchers were among the first in the U.S. to grow the actual virus in the laboratory, a critical step in development of new tests and experiments that will help us understand the disease even better," Daly said.
While PED and TGE viruses are very similar to each other, Daly explained that the diseases caused by them are very similar also.
"Diarrhea, most severe in young piglets, is the hallmark of infections with PED. This diarrhea often results in severe dehydration and death in pre-weaned pigs. Milder clinical signs are noted in older animals," he said. "Even though PED is very closely related to TGE, immunity to TGE, through previous exposure or through vaccination programs, does not confer resistance to PED. There currently is no vaccine against PED."
144 herds tested in South Dakota
At SDSU to date, over 1,800 samples have been submitted and tested for PED since the emergence of the virus. From South Dakota herds, 168 samples have been tested as of November 4, 2013 with no positive results. The previously mentioned South Dakota positive samples were detected at other diagnostic laboratories.
Daly said this would indicate either that producers and veterinarians are cognizant of the disease and do not see the need for diagnostic confirmation, or that there simply are not many suspect cases in our area.
"Reports from regulatory and local veterinarians would suggest that the latter case may be more likely," he said.
He added that basic biosecurity procedures should be effective in keeping the virus out of non-infected premises. The more familiar, but closely related, TGE virus infections typically occur more frequently during fall and winter months. If PED behaves similarly, swine producers and veterinarians may need to employ heightened vigilance as the seasons change.
"Attention to personnel and vehicle traffic, in addition to proper animal movement and isolation protocols, should be reinforced with all farm personnel," he said. "However, producers and veterinarians should keep in mind that our state's swine herd would be very susceptible to infection with PED, having no previous exposure, making biosecurity efforts more important than ever."
If cases of PED are suspected, Daly said producers should work with their veterinarians to determine the best diagnostic strategy.
"It's important to the industry that suspect cases get promptly investigated and confirmed with diagnostics in order for us to better understand how PED is affecting our US, and South Dakota's, swine populations," he said.