Properly maintained and working filtration systems go a long way to keeping aerosoltransmitted pathogens from infecting hog barns

Properly maintained and working filtration systems go a long way to keeping aerosol-transmitted pathogens from infecting hog barns.

Hog barn filtration system audits imperative to disease control

Filtration systems can only prevent the spread of diseases to swine herds if the systems are thoroughly inspected on a daily basis.

Porcine reproductive and respiratory syndrome virus has caused U.S. hog farmers hundreds of millions of dollars in losses in the breeding and growing herds, and new strains of the disease continue to make it hard to battle. Research has proven that filtration systems are effective in reducing, or even preventing, the airborne spread of PRRSV.

Under ideal conditions, for PRRS aerosol transmission that is, PRRS virus has been known to travel up to almost 6 miles. Research concluded in 2012 showed that herds in unfiltered barns were 7.97 times more likely to become infected with PRRSV, as opposed to those in filtered barns. That study also showed that when filtered herds did break, there was a 30-month span between breaks, compared with 11 months between breaks in unfiltered barns.

Even with the backing of that research and the financial wake-up call, Aaron Lower, a veterinarian with Carthage Veterinary Service in Illinois, says getting managers or farm owners to buy into the need for a filtration system can be a tough sell.

“Pig barns are high maintenance,” Lower says. “When we first put the filtration systems in sow farms, we still had a lot of pretty apathetic farms out there. Farm managers see it as an additional piece of work that they have to get done and additional oversight, and [they don’t really] have a lot of resources and tools to get it implemented right.”

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To head off such concerns, Lower says his firm holds “kickoff” meetings to convince the farm teams that filtration does work, as well as to receive feedback from the farm as to barriers to implementation. “We can’t go in there and lecture to them,” he says, recognizing that each producer is motivated by different concerns. “We have to learn from them what the barriers are” in their apprehension toward installing a filtration system. For some it’s the maintenance issue; for others it’s the cost, while others present a manpower issue.

Lower presents ground rules for the kickoff meeting. “We are solutions oriented,” he says. “We will not tolerate complaining or defeat. We are there to make the farm managers successful.”

Making a push for a filtration system in new construction may be an easier sell, since it can be built into the design. Retrofitting an existing barn is not impossible, but it does present different issues altogether.

For those producers who will not buy in just from the raw data supporting filtration success, Lower says it’s beneficial to show them how filtration systems should work. He shares videos using a smoker to simulate how PRRS particles can move into a barn, or better yet, how they do not move into a barn.

“At the end of the day, you’re buying an insurance policy,” Lower says.

Once the buy in from the farm owner or manager has occurred, then the work is merely beginning.

For a ventilation-filtration system to be effective, it has to be in peak working order, and that takes vigilant observation by farm staff. Lower suggests that one or two people on the farm be tasked with daily observation of the filtration system. If a farm’s manpower allows, Lower says it is best if the person (or persons) in charge of managing the system is dedicated to maintenance, rather than using a worker who also has pig care duties. “You know that that person will be called away from checking the filtration system when it’s time to process pigs,” he says. Each filtered farm should commit at least 50% of a full-time equivalent position for filter maintenance, with the other half doing minor maintenance and preventive maintenance.

This person’s workday should begin, if daylight allows, by doing a walk and observation around the outside of the barn. This walk needs to have a purpose — looking for any gaps or openings that would allow dirty air to get inside the barns. The daily inspection should then move to the employee entry, followed by checking loadout and dead drop, farrowing, gestation, the gilt development unit, the disinfection chamber and the pressure washer room. “You need to be looking very thoroughly for anywhere that dirty air can get into a barn,” he says.

The farm’s on-site filtration manager needs to pay close attention to specific elements during the daily walk-arounds, such as making sure chutes collapse properly, creating a good seal. Ones that do collapse, but do not seal, should be adjusted on the fan cone to ensure a better seal. If the chute is damaged, it needs to be replaced.

Chutes can also be blown off of variable-speed fans, and in such cases, a replacement chute should be installed, or the fan can be put on a manual setting if a chute is not immediately available. Other clearly visible indicators of air leaks appear on cracked fan housings, or a broken shroud on a fan so a wind chute would not be able to provide a proper seal. Fans with wind chutes also need to have the weep holes plugged with a rubber stopper.

Lower says all louvers in shutters should be in place and fully closed to prevent backdrafting. A minor crack in a louver can be enough to allow dirty air to enter the barn.

“This involvement really helps develop the farm ownership,” Lower says.

Don’t forget the office
One of the most difficult areas to filter “and feel comfortable about” is the office, Lower says. The reason for that is on most farms, the office is a busy place with lots of opportunities for air penetration including the heating, ventilation and air-conditioning systems; dryer outlets; exhaust vents from bathrooms and showers; and supply entry.

For that reason, Lower says the Carthage group began to look at the office more like an external part of the farm, never being able to reach 100% confidence that the office can be totally biosecure. “We want it as air-tight as possible without going overboard, and then put a good airlock between the office and the farm.”

Lower says that will be a positive-pressure room, so when employees leave the office they step into the clean room. “If there is dirty air in the office, it will stay in the office. The risk to that would be if you have dirty air in the office and it’s physically contaminated on hands or boots, that system will not work for that.”

Producers looking at new construction will have the ability to make the office area more secure than producers looking to retrofit an existing barn.

Though it’s important to identify and remedy any and all possible areas where dirty air can penetrate a hog farm, Lower says too often producers get hung up on areas that are more visible and may be seen as a quick and easy fix.

“Idle fans with unfunctional backdraft protection will let in more air than people do,” Lower says, indicating what may appear to be an evident source of dirty air may actually be of secondary concern that may be missed if the daily inspections are overlooked.

Another layer of observation
In addition to the on-site filtration manager, Carthage has recommended an audit monthly, or more frequently, by a system filter technician (SFT), someone within a hog system to oversee the filtration of all the farms under the system’s umbrella. SFTs go through the same steps as the on-site technician, mainly to provide another set of eyes. “I can go through a site one day, and you could come through the next day, and you could catch some things that I did not catch the day before,” Lower says. The SFT completes an audit with the on-site technician. “This walk-through you’ll want to have a caulk gun and duct tape to fix whatever the system filter tech will find,” Lower says. “There’s no way that they’ll make a complete checklist of things that need to be repaired. The follow-through may not be so good. It’s better to fix as you go.” 

In addition to being another set of eyes on the farm’s filtration system, Lower says the SFT audits the system as well as auditing and coaching the job of the on-site technician.

Still another layer of auditing is a monthly audit by the herd veterinarian who walks through with the SFT. The main purpose of this is to coach the SFT on how they prepared for the audit, audit processes and decision-making, and to see how the SFT interacted with the farm team.

Obviously, implementing a filtration system into a hog operation is a big decision, and one that cannot be taken lightly. Each producer has to take into consideration all of the factors at play in their individual systems.

“A lot of people are concerned about employees’ implementation of the system,” Lower says. “A number of farms have been installing cameras in critical areas, which also works well from an animal welfare standpoint.”

The research mentioned at the beginning of this article shows that filtration lessens the chance of a farm becoming PRRS-infected, but Lower says to think a filtration system is the silver bullet is naïve. “The only true way to protect your farm from aerosol transmission is to shut down your farm and move it, or control what’s going on in your neighborhood” disease-wise, he says. “The only tool that we have to manage PRRS aerosol is a filtration system. So we either have to shut the farm down and move it, or make this system work.” 

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