Just over a year after the virus was first reported in the U.S., the impact of porcine epidemic diarrhea virus has spread to 30 states and killed 8 million pigs, most of them piglets.
That's approximately 10% of the U.S. pig population. In January alone, it killed 1.3 million pigs.
As of mid-June, 7,250 positive accessions have been reported in a total of 30 states, according to the National Animal Health Laboratory Network, or NAHLN. This includes 266 positive accessions in Kansas.
Accessions have declined moving into summer, but National Pork Board vice president of science and technology Dr. Paul Sundberg notes the industry needs to be realistic in its expectations based on PEDV's similarities to transmissible gastroenteritis, another enteric coronavirus.
"What we know from TGE is it will go down over summer, and will come back up over winter," he says. "If it's going to come back, our objective is to keep the peaks down to a lower level than it was last fall and winter."
Challenges in building immunity
Finding an effective way to build breeding herd immunity is a top priority. For years, controlled feedback has been used to build breeding herd immunity to viruses like TGE. This involves exposing sows to the virus to produce antibodies in colostrum.
In the last year, however, producers reported incidents of re-infection of PEDV after sows had been previously exposed, mostly in younger parity sows.
National Pork Board-funded research conducted by the University of Minnesota has shown that the sheer concentration of the virus shed, even in a single gram of feces, is a likely factor.
"A gram of feces is about the size of the eraser of a pencil," Sundberg says. "If you put that into about 24,000 gallons of water and use that water just to water baby pigs with, it will make them sick. That's how concentrated this is."
New threats on the horizon
It isn't just PEDV that's on the radar now. In the last year, porcine deltacoronavirus, as well as second strain of PEDV, made their way into the U.S. Both new viruses were identified through diagnostic testing after producers reported symptoms similar to PEDV, although less severe.
PDCoV is in the same family, but is of a different genus than PEDV. The second strain of PEDV differs in sequence from the original, and the general consensus is a second strain and came into the country after the first, rather than mutating from the original.
"It is an illustration of the importance of laboratory work," Sundberg says. "It shows the importance of more investigation and diagnostic activity so we can better understand if and how these viruses are changing, or if we are getting new viruses."
This also illustrates the importance of identifying pathways these viruses are using to enter the U.S., another top priority. "If those viruses can find their way into the country, we expect there is an opportunity for others to follow," Sundberg adds.
"If we are going to protect our national herds form other foreign animal and other diseases, foot and mouth disease, classical swine fever, as well as other production disease, we have to find out where our vulnerabilities are, we have to find where our open windows are and close them."