Hog barn fans

Fans are seen from the exterior of a hog barn on the Leon Sheets farm in Ionia, Iowa. A U of M study is examining the pathogens in fan filters trap.

As we’ve all learned this year, physical distance and masking up are ways to stave off sickness. They’re tools pig farmers use to keep their herds healthy as well.

Swine barns are built at strategic distances from each other to keep from transferring disease from one barn to another. As another layer of defense, ventilation systems on those barns are equipped with filters that function much like the mask over your mouth and nose. The filters trap airborne viruses before they can circulate through the barn and possibly make pigs sick.

To test just how effective those filters are, a group of researchers at the University of Minnesota came up with a method for finding what viruses filters were able to hold back.

Over the last decade, porcine reproductive and respiratory syndrome virus (PRRS) has impacted about 28% of the U.S. swine herd each year, according to U of M data. Porcine epidemic diarrhea virus (PED) has been another one to watch since it first hit the U.S. in 2013.

“The PRRS virus has been one of the drivers of having to look for better biosecurity measures,” said Dr. Montserrat Torremorell, a professor at the U of M College of Veterinary Medicine.

She has done extensive research on transmission of PRRS and influenza A. Over the last couple of years, she’s been working with a team of researchers trying to understand more about how those diseases transfer through the air. She wanted to know how often these viruses show up on farms, what distances they travel and what other viruses are in the air.

“The filters are actually a good tool that might help us answer some of these questions,” Torremorell said.

Because the filters operate around the clock, they provide a way to sample what is in the air. But the filters are created to trap harmful material, which made it difficult for the researchers to study what was inside.

“They have fibers that capture particles,” Torremorell said. “Releasing them — they are not designed for that.”

The U of M team came up with a way to extract the viruses. It involves freezing the filters in liquid nitrogen, grinding them, then soaking the material in a chemical solvent in order to extract the virus. The team found strains of viruses in the filters from many of the barns where the pigs remained healthy, confirming that the filters worked as a biosecurity measure against airborne diseases.

While the filters are costly, Torremorell noted that diseases they are trying to prevent are also very costly.

“If you can keep free of diseases two or three years, it pays off,” she said.

The filters, though, are just one pieces of a farm’s biosecurity program, she noted. Pig farmers also need to be sure trucks and trailers visiting the farm are clean, employees shower in, and equipment from other farms is isolated.

“This is one piece of the biosecurity puzzle,” she said.

Torremorell’s team is taking its virus extraction method and applying it to further research on disease transmission. They’re currently working with pig farmers whose herds are negative for disease. They are collecting filters used on those farms after they’ve been in place for six months.

They hope to get a better sense of how frequently farms are challenged and what types of viruses are showing up. It’s possible some virus strains mutate to become more transmissible by air, Torremorell said.

Janelle is editor of the Tri-State Neighbor, covering South Dakota, southwestern Minnesota, northwestern Iowa and northeastern Nebraska. Reach her at jatyeo@tristateneighbor.com or follow on Twitter @JLNeighbor