By Joseph F. Connor, DVM, MS
Carthage Veterinary Service, Ltd.
Carthage, Illinois

Each swine disease event — whether it’s porcine epidemic diarrhea virus (PEDv) in the US or African swine fever in Asia — motivates those of us in the pork industry to further improve biosecurity. The ultimate goal is bioexclusion to prevent economically important pathogens from entering a specific population, region or continent.

We’ve known for quite awhile that people pose a huge risk to biosecurity, which can be minimized with a Danish entry or with a shower-in set up. We know that feed delivery-truck drivers should be required to put on new booties or spray their boots before getting out of their trucks to unload.

In other cases, however, we’ve underestimated some of the multiple ways pathogens find their way into our herds. An example is feed. We didn’t understand that some viruses can survive in feed or that some feed ingredients may protect or even enhance viruses.

Overall, conventional biosecurity protocols have been intensified, but they need to be continually reviewed. They also need to be simple and easy to understand and execute. They need to work around the likely failures that pigs and humans present. Personally, I’ve always found it helpful to draw a box around a site, list all of the entries and exits, and define activities that will reduce pathogen introduction.

Weaknesses

Even though we’re developing a better understanding of the risks posed by transport, feed, water and air, there are still areas of weakness that lead to biosecurity failures. I’ll give you an example, and it has to do with changing shoes.

Requiring a shoe change and use of a well-designed bench designating the dirty and clean areas is very common when entering breed-to-wean and wean-to-finish populations. However, if you’re like me and wear shoes I have to untie and pull off with my hands and the shoes are contaminated, my hands become contaminated.

Showering properly will remove the risk from hands, but if before showering I were to handle my shoes, then hand over a lunch bag or food container, the contact risk of contamination remains. To minimize this risk, include an extra step: Apply a sanitizing handwash after the lunch container is dropped in the designated location and before entry into the shower.

Lunch containers are often placed in a UV chamber to disinfect them, but numerous studies have shown that shadows can block the UV light. In addition, UV light does not penetrate containers. The result is inadequate protection if contamination is present.

Transportation risk

Several years ago, a group of us conducted a study involving environmental sampling of pig transport trailers before and after pigs were unloaded at six harvest facilities in the central US.¹ Before unloading, 6.6% of 575 trailers were contaminated with PEDv. Of the remaining trailers that were not contaminated before unloading, 5.2% became contaminated during unloading, indicating the transport process is a source of PEDv transmission if adequate hygiene measures are not implemented.

Transportation is a high risk for pathogen contamination because so many pigs are transported and because it’s difficult to properly clean and disinfect trailers and tractors. There’s certainly better recognition of this risk, and many swine operations have dramatically improved their loadout biosecurity.

Establishing and maintaining a line of segregation or a clean/dirty line is common. However, pigs frequently don’t go in a unidirectional flow, and they don’t remain in the trailer unless barriers such as one-way gates are used. The result is contamination of the contact point between the loadout and the trailer. Consequently, workers track contaminated dirt and manure back to live-animal production.

A practical solution may be installation of flooring such as Tri-Bar that allows additional dirt and manure to drop away from the contact point. An additional valuable step is to require animal handlers to have boots and gloves they use only at the loading contact point. The loadout chute or contact point should be immediately washed, disinfected and dried after every load.

In our facilities, we’ve mounted an electric infrared heater aimed downward to the contact point because drying is an excellent way to inactivate pathogens.

Removal of dead sows

Another common area of challenge is the removal of dead animals. Trucks used to remove animals need to be cleaned, disinfected and dried, and here too, there needs to be a clear line of separation for live and dead transfer.

The clean/dirty line or line of separation is generally well defined for live-animal loading. In addition, newer facilities often have designated drop points that make it easier to maintain that separation. However, the practical removal of a 475-pound sow makes maintenance of that line challenging. This is especially so at older facilities that have collection areas where sows have to be moved from the inside to outside and where more than one person is needed. There’s a common area of cross-contamination.

Practical changes that can be made to minimize the biosecurity risk include rollers in the floor of the dead room so sows can easily be pushed forward. It helps to have porous flooring such as concrete slats or Tri-Bar that lets material drop away quickly and that also is easily washed.

To sum up, there have been tremendous improvements in biosecurity on US swine farms that are backed by practical scientific studies. However, there are still weak spots in our systems, and there are probably routes of pathogen transmission that haven’t even yet been discovered. To protect our herds and maybe, ultimately, achieve bioexclusion, we need to continually strive for biosecurity improvement.

1 Lowe J, et al. Role of Transportation in Spread of Porcine Epidemic Diarrhea Virus Infection, United States. Emerg Infect Dis. 2014 May;20(5):872–874.