22 September 2025

5 minute read

By: Sarah Mikesell

Europe

Dr. Xiaomei Yue, a post-doctoral associate at the University of Minnesota and the Morrison Swine Health Monitoring Project (MSHMP), and Rob Langenhorst, technical sales manager for North America with AAF International, spoke to The Pig Site’s Sarah Mikesell at the World Pork Expo in Des Moines, Iowa, USA about critical new research related to air quality in sow farms and its connection to porcine reproduction and respiratory syndrome virus (PRRS) virus.

Dr. Yue, tell us about your research.

At the Morrison's Swine House Monitoring Project at the University of Minnesota, one of the important things we're working with is PRRS, a worldwide issue that’s been around for several decades.

In 2011, Dr. Bob Morrison started trying to answer the question of whether PRRS is doing better or worse this year versus last year? Also, what is the seasonal circulation of PRRS? He and others at the university started MSHMP to try to better understand the PRRS virus and trends connected to the disease.

Within MSHMP, we have more than 35 production systems in the US, and we monitor about 60% of the US sow farms in 28 states. It's an excessively big dataset, and with that dataset, we were able to collect information like the farm location, farm size, herd size and especially the filtration system used. We know if the farm is yearly filtered, partially filtered, positive pressure filtered, negative pressure filtered or not filtered.

Year by year, our producers keep asking us one question, “Is the filter working for the PRRS prevention?” Together with AAF, we partnered to study and understand if air filtration is helping the US swine producer, especially in the breeding herds, to prevent the PRRS occurrence.

Tell us about your study including the research that you started with and how it was conducted.

For this study, we utilized the MSHMP dataset including 413 sow farms, and the data set spanning from 2009 through 2024. This is more than one and a half decades dataset. After the data cleaning, we had about 238 unfiltered farms, 47 positive pressure filtered farms and 128 negative pressure filtered farms. We wanted to compare the non-filtered farms and the filtered farms in the neighborhood (a 35-kilometer radius). We didn't want to compare the filtered farms in Iowa to a non-filtered farm in Ohio – that doesn't make sense. So, we compared neighbor farms by not only considering the location but also:

• Regional pig density using USDA Census county data
• Number of farms monitored in the MSHMP project
• Herd size

After considering all these important factors then we concluded if positive or negative filtration work compared to the non-filtered farms.

What do the study results indicate?

We are extremely excited to find that the negative filtered farms compared to non-filtered farms had a 51% lower rate of PRRS outbreaks. For the positive filtered farms, it's even better – a 58% lower rate of PRRS outbreaks compared to the non-filtered farms. Both are statistically significant results.

Then, we took a deeper look between the positive filtered and the negative filtered, and we didn’t find any significant differences between the two. We still need a few more years to let the positive or negative show their impact.

Overall, the results we saw were exciting, which showed use of filtration significantly decreases the rate of PRRS outbreaks by more than half.

Switching to Rob, tell us about your filtration solutions.

AAF is the world's largest filtration company, and the swine industry's leader for filtration for sow farms. PRRS continues to be a devastating disease for the industry and strains today keep getting worse. What we're finding and as the study shows is: filtration works.

We offer a full line of filters, grids and filter housings. We're able to help you design your systems. We do all the calculations for you. If you need us to visit farms or come on site to have a bird's eye view perspective, we can do that as well.

I spent six years in the industry prior to coming to AAF as a filtration and biosecurity manager for one of the larger swine producers in the country. I've seen thousands and thousands of filters, and as Xiaomei said about the negative and positive pressure farms, that system also had both. So, I've had experience on both types and there are pros and cons to each. I can express those to the customer as well. It's really a management decision as to which one to go with based on your farm, not which one's better.

How do different filtration systems work to mitigate PRRS transmission?

We said filtration works. It's a preference of how you want to manage that, and we can help design the system and ensure all the air is coming through the filters and its clean air coming in the farm. We know that'll be successful.

Since every farm is different, it seems like you’d need to look at each farm to then find the best system for them, right?

We do that almost on a weekly basis. I emphasize that when customers come to us inquiring and want to set up a team meeting, often we need to go in person and sit down at the table with them. We're more than willing to do that, but it's particularly important to know the details and your expectations of the farm design to truly match the correct products to make sure that the filtration system matches the farm’s needs.