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As the world deals with the COVID-19 pandemic, SHIC continues to focus efforts on prevention, preparedness, and response to novel and emerging swine disease for the benefit of US swine health. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. SHIC is funded by America’s pork producers to fulfill its mission to protect and enhance the health of the US swine herd. For more information, visit https://www.swinehealth.org or contact Dr. Sundberg at [email protected].
Since African swine fever (ASF) was diagnosed in China in August 2018, veterinarians have been studying the virus’s characteristics and learning how to manage in barns. The Swine Health Information Center (SHIC) is monitoring these processes as part of its mission of preparedness for foreign animal disease management for the US national herd. Two US-based practitioners have experience with ASF management practices in China and shared their perspectives with SHIC. Joe Connor, DVM, founder of Carthage Vet Service, believes knowing about transmission of the virus has helped practitioners in China institute a test-and-removal strategy for effectively managing ASF spread. Keith Erlandson, DVM, works in pork production in China and shares their strategy for test-and-removal. Both cite the slow spread of ASF as the key factor enabling successful test-and-remove protocols.
This successful experience in China contains great value for American swine practitioners. “This is teaching us we need to move to the next step of biosecurity, which is biocontainment, which can apply to other viruses and bacteria we see,” remarked Dr. Connor. “It’s a matter of changing mindset. What can we do in the next generation biosecurity which is biocontainment? Think in terms of individual population effect on larger adjacent populations.”
Using the USDA grant received last fall to open ASF dialogue and research in Asia, SHIC is beginning projects focused on test-and-remove protocols during work conducted in Vietnam, with the intent to measure efficacy and provide guidance for similar biocontainment practices for domestic herds. The experience in China is also informative to the process.
“The idea is to stop transmission because the virus moves relatively slowly,” Dr. Connor explained. “So what we see has developed in China is, through experience, better detection of early clinical signs of an animal that is infected. Second would be readily available PCR diagnostics so they can very quickly confirm a yes or a no. Third, they lockdown that gestation area (with infected animal(s)) by individual stall or stalls if there’s a solid pen divide between groups, or if there are no solid dividers between the stalls, the lockdown is by the trough. If the suspect or positive animal is in finishing, they lock down the individual pen with the animal and the pens on each side. In both situations, they lock down the barn until further testing can be done and decisions made. When they have a suspect animal or animals and are waiting for confirmation, they totally lock that building down for people movement, traffic in and out, and animals in and out, until they get confirmation of a yes or a no. Fourth, they take great care in removing those positive animals to prevent transmission. They have learned to focus on containment to stop the spread.”
Dr. Erlandson has been directly involved with successful test-and-removal management of ASF. “When ASF initially broke, we were of the mindset that we needed to eradicate it. Anytime ASF broke on a farm, we would euthanize the whole population, clean and disinfect the premises, and start over,” he stated. “When it became clear ASF was going to become endemic, depopulation just because we had a positive test was not an economically viable solution. Due to the economics, we, among others, started working on test-and-removal. What we found is the virus does not spread as quickly as we were originally led to believe, especially in a sow herd where animals are individually housed.”
Drs. Connor and Erlandson agree the first step for successful test-and-remove protocols is recognizing the clinical signs of ASF in pigs. This requires frequent and repeated education for direct-care workers. “I thought if you walked onto a farm with ASF you would know it instantly, but that’s not what happens. Initially, there may be only one or two animals infected, the mortality of one or two animals may not even be noticed. The disease often doesn’t raise alarms early on, so there is the chance of missing early cases if you are not vigilant,” Dr. Erlandson said.
Dr. Erlandson said sows being off feed is an automatic trigger for ASF testing in barns under his care in China. Testing is done by oral swab. He said this testing process is relatively easy for all staff to do as compared to collecting blood or serum. However, positive oral swab results leads to whole blood or serum PCR tests.
“I think one of the big reasons finisher farms get infected is by contamination from the truck taking animals to slaughter,” Dr. Erlandson observed. “Of the finishing cases I’ve seen, I believe 70% to 80% of the breaks are due to transportation to the slaughterhouse. When a site with market age pigs breaks, you euthanize any animal with clinical signs and get everything else on the truck to market as soon as possible.” What follows is cleaning and disinfecting of the barn before new animals arrive. For younger animals, Dr. Erlandson says they are assessed and whole pens where clinical cases are found will be euthanized as well as pens on either side as appropriate. Testing occurs frequently and close monitoring for clinical signs continues.
Using test-and-removal protocols based on farm design has been successful for Dr. Erlandson’s company. “Depending on the situation and how quickly ASF is recognized, I have seen a success rate of 70% to 80%,” he reported. “After a test and remove, generally we want three weeks of clean testing and cleaning and disinfecting of the farm, after which the farm can open back up.”
The Swine Health Information Center (SHIC) remains intent on learning everything possible about African swine fever (ASF) management and control. These lessons will be valuable if ASF enters the US and are part of SHIC’s preparedness mission. A $1.7 million USDA Foreign Agricultural Service grant awarded last fall to SHIC, with active support from the National Pork Producers Council (NPPC), is funding ASF research which will benefit both US and Vietnamese pork producers. The grant’s overall goals include sharing veterinary knowledge and ways to prevent ASF from further spreading, while also helping to build veterinary capacity as well as strategic partnerships, and increasing trade of US pork to the region. So far, six related research projects will begin. Some are under contract with SHIC using grant funds and others are potentially being funded by the National Pork Board (NPB). In addition to these six, there are more to come. “This is a competitive process involving outside reviewers looking at priority per the call for proposals, objectives, and budget in selecting for funding,” remarked Dr. Paul Sundberg, SHIC executive director. The first six ASF-related research projects include field evaluation of oral fluids for detection of ASF, the validity of test-and-remove practices with ASF, examining rodents as vectors for ASF, time and temperature required for inactivation of ASF virus, composting for ASF inactivation, and methods for decontamination of truck cabs.
Field evaluation of oral fluids as a convenient, aggregate sample for early detection of ASF
A field evaluation of using oral fluids for detection and surveillance of ASF virus will be conducted in Vietnam. Pen-based aggregate oral (rope) fluid testing is a non-invasive, common US industry practice requiring significantly lower financial and human resources than other methods. Collaborators on this project are the Canadian Food Inspection Agency – National Centre for Foreign Animal Diseases, Vietnam National University of Agriculture, Iowa State University, National Bio and Agro-Defense Facility, USDA Animal Research Center, and Plum Island Animal Disease Center. Funded by SHIC with USDA grant proceeds.
Using standard laboratory PCR testing, and comparing available point of care (POC) technology, to assess the validity of current ASF test-and-remove practices in commercial swine farms within Vietnam
The test-and-remove protocol is based on the premise that ASF, although highly infectious, has relatively slow transmissibility. The process involves immediate removal of any sow exhibiting clinical signs, submitting blood for ASF detection by PCR, and if the animal is determined positive, adjacent animals (two up and two down the trough from the sow) are also removed. This project will test sufficiency of this methodology for ASF elimination in the Vietnamese sow herd, while in the process testing four commercially available ASF point-of-care (POC) assays on diagnostic performance for detecting ASF in suspect and non-clinical neighboring animals. Researchers working on this study are from Boehringer Ingelheim, Iowa State University, and Nong Lam University. Funded by SHIC with USDA grant proceeds.
Time and temperature required for complete inactivation of ASF virus
This research being conducted by the University of Nebraska and Vietnam National University of Agriculture, is designed to simulate the sanitation protocols currently used to disinfect animal trailers, with the goal of identifying the optimal baking time and temperature required to completely inactivate ASF virus in contaminated aluminum materials. Funded by SHIC with USDA grant proceeds.
Potential of rodents to be a vector in the transmission of ASF in two commercial farms in Vietnam with differing biosecurity levels
This project is designed to determine if ASF virus can be detected in mice and rats, a potential threat of transmission. Then, if so, which tissues of mice and rats are best to sample. Next, the project will determine the impact of farm biosecurity level on rodents’ ability to carry the disease, confirming whether stringent biosecurity reduces rodent movement as compared to farms with less stringent biosecurity and older buildings. Finally, researchers will measure mouse-to-mouse transmission of ASF in a controlled, laboratory situation, determining if ASF can be transmitted between mice through direct physical contact and/or contact with feces from ASF-infected mice. Collaborators on this project are from South Dakota State University and the Vietnam National University of Agriculture. Funded by SHIC with USDA grant proceeds.
Investigating methods for decontamination of interior surfaces (cabs) of transportation vehicles
A recent report of a field investigation in Vietnam by Kansas State University (KSU) staff indicated the cabs of vehicles responsible for feed delivery and live animal movement are a common area of ASF virus contamination. This research conducted by KSU will develop a cab decontamination model that stimulates the air volume and surface type cab environment of a truck cab, then evaluate a series of procedures for efficacy against porcine epidemic diarrhea virus (PEDV) and ASF virus. The process will include testing in Vietnam in collaboration with Vietnamese production partners. The intended outcome is practical, efficacious, and cost-effective solutions for swine producers to address the risk of contamination of cabs from numerous pathogens within a wide variety of vehicles. This project is being reviewed for funding by the National Pork Board.
Validating the composting process for ASF virus inactivation
In validating the composting process for ASF virus inactivation, the research will help US pork producers collect data to improve ASF outbreak response readiness and help Vietnamese pork producers better respond to and recover from ongoing ASF outbreaks there. The project team will conduct research in Vietnam to assess the effectiveness of swine carcass composting in inactivating the ASF virus and assess time and temperature requirements. The University of Maine System acting through the University of Maine, along with an industry consultant, USDA APHIS staff, and personnel at Vietnam National University of Agriculture in Hanoi are collaborating on this work. This project is being reviewed for funding by the National Pork Board.
These research projects, as well as others to be contracted and announced, all share the mission of benefiting both US pork producers with resources for readiness for reacting for foreign animal disease such as ASF while also providing much-needed information for Vietnamese producers already facing ASF infection.
The Swine Health Information Center (SHIC) is aware of continuing stress in the swine industry caused by the COVID-19 pandemic. The following pages contain resources for producers and industry partners.
As the world deals with the COVID-19 pandemic, SHIC continues to focus efforts on prevention, preparedness, and response to novel
and emerging swine disease for the benefit of US swine health.
In the June Domestic Swine Disease Monitoring Report, we learn the overall percentage of porcine reproductive and respiratory syndrome virus (PRRSV) positive cases in May was similar to the previous month. Wean-to-market cases were slightly up. Comparing January – April 2020 to the same four months of 2019, the number of PRRSV cases was up 6.49%. The overall percentage of porcine epidemic diarrhea virus (PEDV) RNA-positive cases in May was down compared to April, however, this was not the case for the adult/sow category where detection remained similar to the prior month. The overall percentage of porcine delta coronavirus (PDCoV) positive cases in May was down compared to April as well and within forecasted levels for this time of year. Mycoplasma hyopneumoniae (MHP) positive cases in May were within the forecasted levels, also.
In the June Global Swine Disease Monitoring Report you will read about USDA updating its African swine fever (ASF) Strategic Plan. Learn more about ASF in wild boar in Europe and the Pirbright Institute’s progress on an ASF vaccination. In Switzerland, the concern is the first recurrence of PRRS since March 2014.
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