Where there is hog manure, there is the potential for porcine epidemic diarrhea virus (PEDV) to find its way into a hog operation. That’s an especially daunting fact because the virus sheds at extremely high levels and very little virus is needed to infect pigs.
“The very low infective dose of PEDV surprised me the most,” says Sagar Goyal, DVM, University of Minnesota researcher, who looked at the virus’ survivability in various environmental settings. “We proved the infectious dose of PEDV to cause disease in pigs is very low (even 10-8 dilution of the virus infected piglets).”
In a Pork Checkoff-funded study, Goyal looked at PEDV survival in fresh feces, manure slurry, drinking and recycled water, and ground feed. Overall, he found results similar to those for TGE (transmissible gastroenteritis virus)—a related coronavirus. Here’s a snapshot of the PEDV results:
· Survival in fresh feces: The study evaluated PEDV survivability at three temperatures (104 F, 122 F and 140 F) and three relative humidity levels (30%, 50% and 70%). The bottom line: “If feces from infected pigs are present in the barn, the virus can survive for 7 days or more,” Goyal says.
· Survival in manure slurry: PEDV infected slurry was stored at room temperature (approximately 77 F), 39 F and -4 F. At room temperature, PEDV survived in manure slurry for 14 days. At 39 F and -4 F, PEDV survived for 28 days, and possibly longer, Goyal says, as the study didn’t continue beyond that point. “So, if you use manure slurry for land application, you need to understand that the virus can survive in an infectious state for 14 to 28 days, maybe more,” he says.
· Survival in drinking and recycled water: Both water options spiked with PEDV were evaluated at room temperature over a series of weeks. The virus survived in both water sources for one week, but not two. However, Goyal points out that since the study didn’t test daily samples, survivability could extend beyond 7 and up to 13 days.
· Survival in feed: The study evaluated wet and dry ground feed dosed with PEDV and stored at room temperature. PEDV remained viable in the wet feed for 28 days (again, the study didn’t run longer). In dry feed, the virus survived only one week. So, if contaminated feed is a concern, Goyal says storing it for two weeks at room temperature will kill the virus. “However, we don’t know if colder temperatures enhance survival,” he adds. It’s also important to note that the pigs received only 15 g of PEDV-spiked feed—“and pigs eat more than that, so we need to look at what happens when feeding larger quantities,” Goyal says.
His lab has just concluded a water chlorination study to determine if it offers protection against PEDV exposure; those results will be available soon.
“My advice to producers is to pay attention to the virus survivability results. If it survived one week in experimental conditions, I would double the time just to be on the safe side,” Goyal says.
From a practical standpoint, Butch Baker, DVM, Iowa State University, endorses that sentiment. “My experience with TGE is if the virus is down in a nice dark spot and it’s wet, the virus can survive longer than two weeks,” he says.
Biosecurity measures and clean barns must be a priority, Baker contends. “There are clean barns and then there are barns that are said to be clean-- they are not the same. You have to empty and clean out facilities-- and that includes waterers and feeders,” he says. “You have to get the biofilms out of there, and it does take a considerable effort.”