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Boar stud targeted biosecurity against African swine fever

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Targeted-biosecurity protocols are resource intensive but important for FAD control; feasibility, cost, and effectiveness must be considered.

If an introduction of African swine fever was to occur in the United States, the profitability and viability of all swine premises would be in jeopardy, and that includes boar stud units, says Kaitlyn St. Charles, a risk analyst for the Secure Food Systems Team at the University of Minnesota College of Veterinary Medicine.

To prevent the introduction of ASF into any swine premise, St Charles says standard industry biosecurity, and even enhanced biosecurity recommendations, may not be enough to mitigate disease entry pathways.

"Oftentimes, normal biosecurity that succeeds at keeping out specific endemic diseases might not be able to hold up to the new disease challenges we face," St. Charles says. "There can be higher consequences for foreign animal diseases, such as ASF, versus endemic diseases, and so with these new burdens that are placed upon our biosecurity measures, we really want to start thinking about how we can reinforce our current biosecurity." 

While most farms implement industry standard biosecurity practices and some have begun putting enhanced biosecurity plans in place through programs such as Secure Pork Supply, St. Charles says to reduce the likelihood of an FAD entry, the use of evidence-based, pathogen-specific biosecurity that is feasible for specific commodities — known as targeted-biosecurity — will be needed.

"We're layering on the industry biosecurity; we're layering on the enhanced biosecurity; and we're targeting these control area farms. They're in that high-risk area, now we're tailoring additional biosecurity mitigations to fit that specific FAD pathogen in which there’s already an infected index farm," St. Charles says. "We're also tailoring our biosecurity for the specific commodity type, the specific sector type that we are, and then we are tailoring our biosecurity around the specific movement of products that leave that farm."

To determine what a targeted biosecurity program for a boar stud premises would need in a control area during an ASF outbreak, St. Charles and her team set out to conduct a risk assessment, including components such as a hazard identification assessment and a pathogen entry assessment. The team completed an extensive literature review and assessed the current production, movement and biosecurity practices of boar studs within the United States. They held meetings with and surveyed a public-private workgroup that included boar stud industry members and subject matter experts as well as animal health regulators. They identified enhanced biosecurity recommendations from established programs, constructed disease entry pathways onto a boar stud site, and assessed the efficacy of biosecurity mitigations.

The final step conducted was to combine the assessment of the efficacy of standard and enhanced biosecurity practices in relation to specific disease entry pathways and the known host-pathogen-environment interaction mechanisms. Results of this step allowed the team to identify biosecurity gaps and additional pathogen-specific mitigations that are needed.

Upon completion of the final step, the likelihoods of ASFv entry were assigned ratings using a likelihood rating scale utilized by the World Organization for Animal Health for risk analysis. Working group stakeholders determined if the ratings were acceptable (e.g., within the range of "negligible" to "low"), and in cases where they were not acceptable, ASF- and commodity-specific mitigations were proposed.

Of the 14 ASFV-entry pathways identified, six were found to require ASFV-targeted biosecurity mitigations to reduce the likelihood rating of entry to a level that was acceptable to industry and regulatory stakeholders. These pathways included ASFv entry via feed, people as mechanical vectors, fomites, mortality management, domestic animals (including replacement boars) and biologics.

"In boar studs specifically, we're worried about replacement boars. Boar studs already are pretty good with their industry standard biosecurity, they have replacement boars coming from high health status herds already and they're going into a quarantine unit for pretty much a minimum of 30 days, which is great in terms of being able to pick up ASF clinical signs within that time," St. Charles says. "But something we can do to kind of bolster our ability to identify any ASFv-infected boars before they start producing semen is making sure when we're moving boars from the isolation unit to the main herd, that we're doing an all-in all-out practice, so we're testing 100% of that population prior to the move if it's not being done already."

When it comes to mortality management, St. Charles says boar stud units also do a pretty good job already of managing mortality on site, and dissuading scavengers from coming in, but prohibiting rendering with no exceptions would be another protocol to add during as a stud located in a control area.

"Not that many boar studs use rendering to begin with, but for the handful that do, just saying, no, you cannot use that as a means of mortality disposal during an outbreak," St. Charles says. "Then we're mitigating potentially infectious animal mortality from coming onto a site or contaminating anywhere near the PBA, and then we're mitigating those people and vehicles who/that could potentially become contaminated as well."

Other examples of ASFv-targeted mitigation measures for boar stud units would be to implement to ASFv-specific disinfection and downtime requirements for all incoming supplies and equipment and to adjust semen delivery procedures so that no direct deliveries to sow farms are taking place during an outbreak.

St. Charles noted while the team focused on lowering the likelihood ratings for these six pathways for introducing ASF into a boar stud unit, they're also looking at the biosecurity around the likelihood of a ASF release from a boar stud located in a control area as well as looking at the likelihood of detecting ASFv-infected boars prior to semen movement.

Since targeted biosecurity is almost always energy, resource, and time intensive compared to industry standard, and sometimes even compared to enhanced biosecurity recommendations, it will also require commodity or sector consensus.

"We can come up with all of these great ASFv targeted mitigations, but if they're not feasible for a boar stud, they're simply not usable," St. Charles says. "And they're not going to do a very good job of actually mitigating against an ASFv introduction or release, hence the importance of that work group component to the risk assessment and determining biosecurity mitigations."

Additionally, targeted biosecurity is an important compliment to surveillance testing protocols during periods of high risk.

"If you've heard of the concept of a premovement isolation period prior to the movement of live animals, that scenario involves really heightened and targeted biosecurity in tandem with testing, and has been used extensively in the poultry industry during FAD outbreaks, specifically in the context of highly pathogenic avian influenza outbreaks," St. Charles says.

Many targeted biosecurity measures that work for one pathogen, one species, one commodity or sector can work well for other pathogens, even if they are not targeted necessarily, she says.

"But the thing about that is to just to keep in mind whenever we're using biosecurity mitigations, we  need to be going through the assessment process and really double checking with the comprehensive knowledge of that pathogen of concern, of that context, of that movement, that the biosecurity is actually effective, and we're not just making assumptions based on things we've used for other diseases and commodity types," St. Charles says. "An example of that is in the Secure Poultry Supply Plans, a lot of the recommendations and permit guidance that poultry producers use when they are moving products within control areas are harmonized across species and across commodities, but the efficacy of the harmonized measures are verified within their specific product and commodity risk assessments."

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