CARTHAGE, Ill. — Colder temperatures that are settling over the Midwest are the next question mark for those monitoring the spread of PEDV, porcine epidemic diarrhea virus.

“We have not gone through a winter with the virus,” said Dr. Joe Connor of Carthage Veterinary Services, based in Carthage.

Cold weather and harvest-time activities, including emptying manure pits and lagoons, could be contributing to the spread of the swine-specific virus that mainly impacts suckling pigs.

“The virus has been environmentally hardy. It actually moved in certain areas very actively this summer even when we had high temperatures, but typically if we compare this virus to (transmissible gastro enteritis), and looking at the environmental survivability, we expect that it’s going to stay viable in below-freezing temperatures, so as we enter the cold season, then the likelihood of it remaining viable — which then makes it easier to transfer — increases,” said Connor, who noted that PEDV has been endemic in Asia for several years and has survived cold temperatures.

Connor said there has been a spike in cases in recent weeks.

“The number of cases continues to increase, particularly in the original active areas of Iowa, Oklahoma and then, more recently, in North Carolina. We had a little bit of a slowdown in September, but in the last few weeks, there’s been an increase in cases in many states of the Midwest,” he said.

Connor said that as of Oct. 6, Illinois had a total of four cases and Indiana had 26 cases of PEDV reported.

Through Oct. 24, 828 case submissions tested positive. However, Connor cautioned that the number likely includes repeated submissions from the same herd and so would not accurately reflect the number of actual farm sites affected.

Harvest time brings a perfect storm of factors that are conducive to the spread of PEDV.

Connor said the virus survivability tends to be better in cooler temperatures.

“We’re finishing up and would have been in the middle of harvest where we would have had maybe increased transmission. We’re removing slurry from pits and lagoons, so we’ve got application occurring,” he said.

Connor said a movement of pigs to slaughter also could contribute to the spread of PEDV, through transmission by vehicle.

“Those pigs may or may not be transmitting, but it’s likely that the number of transporters, trailers, that would be positive or contaminated with infected pigs has increased. That then increases the risk that we have at any of the drop-off points, whether it’s a slaughter plant or a cull sow plant or cull sow buying station,” he said.

Connor emphasized that the virus poses absolutely no threat to humans or to the U.S. pork supply.

“It is absolutely no risk to humans and no risk to pork. It is primarily only in the intestinal tract,” he said.

He also noted that manure being applied poses no threat, but the danger lies in the movement of application equipment from farm to farm.

“It’s not the application process itself that is the risk. It is that most of the industry uses applicators that would service a number of facilities and so they are going to move from one facility to the next. By the nature of our equipment, you are generally going to have a cycle pump or booster pump that would go down into the pit that would have also been used in another facility,” he said.

Connor said all producers, regardless of the type or size of operation, need to look at their farms carefully to see where they can prevent the spread of the virus through the movement of fecal material.

“I would like to emphasize that there are still steps that we can take to minimize the transmission. Each individual producer should critically evaluate each of those key areas, which would be transportation, whether that’s weaned pigs, slaughter pigs, cull sows or light pigs. Secondly, the movement of manure application equipment. Third, we’ve got to maintain excellent isolation of incoming breeding stock, and we now have a serological test, as well as PCRs, to clear those animals from isolation. Then, with their own staff, adhere to showering, and if they don’t shower going in to facilities, the Danish change, which is a change of boots or shoes, coveralls and washing of hands,” he said.

The industry, including the National Pork Board, has put funding toward research on every aspect of the virus, from how it got to the U.S. to how it moves and survives.

“Because it is primarily transferred through the feces, any method that transfers fecal material would be a method of introduction back into the herd,” Connor said.

He said there has been good cooperation from the processing side to help minimize the movement of the virus on the transportation side.

“There’s been tremendous cooperation trying to minimize what we call the crossover traffic. In many cases, slaughter plants have initiated a hot water wash, the last 10 feet of the loading dock. They have implemented an electronic means of transferring the weight tickets so that the driver does not have to walk across the area where other drivers have walked. There’s certainly been an increase in the number of trailers that have been washed and dried,” said Connor, who added there are recommendations for drying procedures.

“The ones that have drying bays, because this virus is even more environmentally resistant to temperatures than (porcine reproductive and respiratory syndrome), the recommendation is to dry those trailers at 150 degrees Fahrenheit for 20 minutes,” he said.

Connor advised producers to use materials and research available through the National Pork Board’s website or through the American Association of Swine Veterinarian’s website,

“There’s now updated information and brochures for transporters, packing plants, manure applicators, sow buying stations and then a white paper that summarizes how to deal with the virus in a sow herd as you look at trying to eliminate that virus,” he said.

He urged producers in all types of hog operations to stay up to date on the research and information. Connor has been involved in the working groups through the National Pork and the AASV.

“Producers should procure all of that information, and they can also, on, get the research studies that are in process. Those are updated every two weeks to get the latest information as the studies start to wind down,” he said.

Connor said even the operators of finishing facilities need to be vigilant. While PEDV has the most impact and losses in suckling pig populations, finishing facilities also could see outbreaks.

“They all need to pay attention. The difference is that, just by nature of the virus, the high mortality is going to be in suckling pigs. The wean-to-finish population or the nursery population or the finishing population will have a very short-term diarrhea with almost no or low mortality and quite good recovery. Whereas in the suckling pigs, because the herds have not been exposed to the virus, the suckling pig mortality has generally been almost 100 percent for a three-week time period and then it starts to taper off over several weeks resulting in baby pig losses of equivalent to about five weeks’ of production total,” he explained.

Connor said finishing facility operators need to maintain biosecurity.

“We still want our finishers to think about containment and not move it to other facilities they would have onsite or offsite or to any neighbors. Even though the mortality is generally low, the pigs will go through a period of diarrhea for two to four days,” said Connor, who said finishing facilities have the opportunity to be an endpoint for the virus.

“The important thing for the finishing side is if they can contain it to that building or that population of pigs, when they empty that building, then they’ve got the opportunity to eliminate that virus out of the building, but it will take more work, more sanitation, a better, more intense disinfection, but then the next turn of the barn, if they have a negative source coming back in there, then they will have a facility that is clean and a population that would remain negative through the flow,” he said.

He noted that one published report tracked the virus to Anhui province in eastern China.

“There was a published report that it appears to have at least originated from the Anhui province. We have known since the first cases that the virus was 99.46 percent similar to the virus that was identified in China. This is just a further refinement of identifying a little closer the province or location,” he said.

The ultimate goal of the industry is to stop the spread of the virus and eliminate it. Connor said it will take the cooperation of all sectors to do that.

“I’d encourage them to really critically look at the information that’s out and let’s help ourselves and see if we can contain it and eventually move toward elimination,” he said.