The U.S. swine industry wasn’t prepared for porcine epidemic diarrhea (PED) virus when it came into the U.S. in 2013. That’s why the multi-phase African swine fever (ASF) field projects in Vietnam are such an important step forward for the U.S., says Paul Sundberg, executive director of the Swine Health Information Center (SHIC).
“The bottom line about this program in Vietnam is that we don’t want to repeat the mistakes that we’ve made historically,” Sundberg says. “This Vietnam ASF program is all about answering questions that we need to have answered in order to be prepared for if it gets here.”
Although these projects in and of themselves won’t prevent ASF from reaching the U.S. hog herd, information gleaned can make a huge difference in slowing down the virus spread if it does get through the barriers.
These projects are possible because of a 2019 grant from USDA’s Foreign Agricultural Service division, awarded to SHIC who applied with National Pork Producers Council assistance.
Prepare for the Worst
Prevention is critical right now, but Sundberg says our industry can’t just stop at prevention.
“It’s not realistic to just say, ‘We’re going to be o.k., because it won’t come.’ You’ve got to prepare for that contingency as well,” Sundberg explains.
The research in Vietnam allows the industry to get real-time, on-the-ground information and control protocols figured out that couldn’t be mimicked in a laboratory in the U.S. or Canada.
“As a matter of fact, there’s some research information that’s shown what we thought was a good procedure to use to control ASF turned out to be not quite as good as we hoped. That’s the kind of thing we want to make sure we have the best information possible on so we can be prepared to control it should it get here.”
Eradication
Most of the research being conducted in Vietnam is in preparation to assist an eradication program.
“You’ve got to be able to control an infection to eradicate it,” he says. “Should ASF get here and get a foothold and become endemic, we’ve got to find a way to get rid of it. Those are the kinds of lessons we’re trying to learn in Vietnam.”
About half of the projects have been completed, and the rest are ongoing, Sundberg says. Here’s a look at some of the projects completed so far:
One completed study evaluated the performance of ASF serum and/or oral fluid ELISAs for use in the surveillance and monitoring of ASF outbreaks in commercial farms in Vietnam and in preparation for the virus becoming endemic in the U.S. This study shows there is no single best diagnostic approach for ASFV surveillance and demonstrates that the combined use of the Tetracore qPCR and indirect ELISA tests and serum/oral fluid sampling increase efficiency of ASF disease surveillance. Another completed study modeled the risk of introducing ASF to a sow farm as a result of semen movement from apparently healthy boar studs located in an ASF disease control area. Results indicated the risk is negligible to low given study parameters, however, several factors with the potential to impact these results were acknowledged.
Evaluation of the Diagnostic Performance of an ASFV Serum/Oral Fluid Antibody ELISAs Under Field Conditions in Vietnam
This study evaluated performance of these tests for surveillance and monitoring of outbreaks on commercial farms. A collaborative project between Innoceleris LLC and Tetracore Inc., the work addresses the complicated interpretation of ASF diagnostic results. A field team from Hanoi University collected 398 paired serum/oral fluid samples from individual animals, including 100 samples from 34 ASF-acute farms, 98 samples from 47 ASF-chronic farms, and 200 samples from 20 ASF-negative farms. The samples were tested by Tetracore ASFV iELISA and real-time PCR (qPCR). As expected, the detection rate by qPCR was higher than by ELISA in acute farms since most of the animals did not yet seroconvert. In contrast, in chronically affected farms, the detection rate of the ELISA was higher than the qPCR. However, when researchers combined both qPCR and ELISA, the detection rate of ASFV positive animal increased in acute and particularly in chronic farms. All serum samples from negative farms were negative by both ELISA and qPCR (100% diagnostic specificity) while, for oral fluids, researchers obtained 100% and 99% diagnostic specificity for qPCR and ELISA, respectively. The high diagnostic specificity of the tests is particularly important for ASF surveillance. Absence of false positives avoids false alarms and disruption in production, and lack of confidence in the tests/surveillance system.
Determining the Pathways for ASF Introduction Into Boar Studs and Risk of ASF Transmission Via Semen Movements During an ASF Outbreak
This study included a proactive risk assessment (RA) that looked at the potential risk of semen movements during an outbreak. Researchers, led by staff at the University of Minnesota, established the ASF Boar Semen RA workgroup (WG). Together with researchers at the University of Hanoi, experts determined and rated 10 potential entry pathways for ASF into boar studs as people, feed, water, geographic and/or aerosol transmission, fomites (such as tools, equipment, vehicles), mortality management, domestic animals (such as dogs, cats, replacement boars), biological materials (such as medicines and vaccines), insects/ticks, and wildlife. Data from a boar stud in Vietnam were also obtained by working with a Vietnamese collaborator who was able to visit the site and perform an epidemiological investigation that included premises description, farm biosecurity, farm help/workers, farm equipment, manure handling, dead pig disposal, farm visitors, presence of wild animals, mortality data, description of the recent biosecurity practices, and a farm diagram.
Of most value were data regarding clinical signs and diagnostic tests. As a result of the pathway analyses, the proposed estimated likelihood of ASFV infection of a boar stud operation in a Control Area due to water was negligible, as long as no surface water is being utilized in the boar stud operation. The likelihood of ASFv introduction was negligible to low for feed, insects/arthropods, and wildlife (including infected feral pigs), as long as boar studs continue their standard biosecurity practices such as tandem feed bins, insect control, indoor housing, and double fencing. The likelihood of ASFv introduction was low for people, fomites, domestic animals (including replacement boars), and biological materials, as long as boar studs continue requirements and procedures including but not limited to shower-in/shower-out people entry with downtime from other pigs, decontamination and disinfection for materials entering the stud, and housing of replacement boars in isolation barns away from the boar stud and lab.
It is important to note for seven potential entry pathways of ASF infection (people, feed, fomites, animals, insects/arthropods, wildlife, and domestic animals), there are suggested Enhanced Biosecurity Recommendations (EBRs) in the Secure Pork Supply (SPS) plan that, if followed and done correctly, are critical to lowering the risk of ASF infection. Therefore, following all EBRs was assumed to occur when these ratings were made, and examples of these biosecurity practices have been given above (for example, shower-in/shower-out). On top of the EBRs in the SPS plan, the WG proposed putting into place targeted EBRs to further reduce the risk of ASF infection. When the WG decided these targeted EBRs were feasible by the vast majority of boar studs in the U.S. swine industry, these protective actions were included in the estimates of the likelihood ratings. This proactive risk assessment will be reviewed and open for comments. The comments will be considered and use to update the risk assessment as necessary before and during an ASF outbreak in order to incorporate the latest scientific information and preventive measures. If the Incident Command System is activated in response to an ASF outbreak, Incident Command staff will have the information to review to help assess industry requests for movement of liquid, cooled boar semen from a boar stud in a control area.
More from Farm Journal’s PORK:
Why the U.S. Pork Industry Won’t Forget 2021
Swine Health Information Center Seeks Associate Director
Close All the Windows to Keep ASF Out
ASF in the Western Hemisphere: What’s Different 40 Years Later?
It’s Time to Batten Down the Hatches, Pork Industry Experts Say
Learn more about what the industry is doing to prevent ASF from entering the country.
