Enhancing passive surveillance will help producers protect their pigs from ASF and other diseases

by Dr. Rachel Schambow

pigs peeking through a fence
The University of Minnesota Center for Animal Health and Food Safety has created an enhanced passive surveillance tool that uses biosecurity, clinical signs, and necropsy findings. Photo Credit: ToonPhotoClub/iStock/Getty Images Plus photo

African Swine Fever (ASF) is not yet present in the US, but this deadly porcine virus has been spreading globally since 2007.

The close proximity of ASF in Haiti and the Dominican Republic coupled with its continued, unmitigated spread throughout Europe and Asia continue to pose a serious threat to the US swine industry.

ASF causes extremely high mortality - close to 100 percent - and ASF-infected countries suffer severe export restrictions. Researchers estimated that an ASF epidemic would result in about US$50 billion in losses to the American swine industry over 10 years due to control measures and lost markets.

If ASF were introduced to the US, finding a potential outbreak as quickly as possible could mean the difference between eradicating the disease or living with it long-term.

Unfortunately, ASF-infected pigs don’t show distinguishing clinical signs and can appear similar to diseases like PRRS, which makes ASF detection difficult.

High mortalities may raise suspicion, but because ASF spreads slowly in a herd, this can be too late to prevent a wide-scale outbreak.

Early detection is critical for mitigating the devastating effect of an ASF epidemic, so to support this goal, researchers at the University of Minnesota Center for Animal Health and Food Safety (CAHFS) are exploring novel ways to help swine producers identify a potential ASF-infected pig on their farms as early as possible.

The CAHFS team developed an “enhanced passive surveillance” (EPS) tool that producers or swine veterinarians can use for ASF and other diseases. Surveillance is the activity of looking for diseases within populations, such as monitoring for PRRS, PED, and foreign animal diseases like ASF.

However, passive surveillance specifically refers to disease identification and monitoring by farmers and their veterinarians, such as reporting suspicious disease clinical signs to an animal health official.

Enhancing passive surveillance with different tools and strategies provides an excellent opportunity to improve the US swine industry’s capacity for early ASF detection and can help support the control and eradication of PRRS and other swine diseases as well.

Working with global ASF experts and with funding from the USDA (United States Department of Agriculture), the CAHFS team developed and piloted an EPS protocol for ASF in 2022.

The tool is based on three components: biosecurity; clinical signs, and; necropsy findings.

Over 10 weeks, two farms in the Dominican Republic used a scorecard system to track the presence of clinical signs and necropsy findings that could be consistent with ASF.

Each week, depending on what signs were present, the farms were assigned a score, and when high enough, this score triggered suspicion that a disease event was occurring.

Over the test period, the signal for diagnostic testing was triggered twice. Although ASF was not detected, the system showed how EPS can act as a consistent, standardized on-farm protocol that improves early disease detection.

The CAHFS researchers are now focusing on how their EPS tool can support early ASF detection in the US.

In 2022, they conducted a series of activities and workshops to understand what swine producers already do for disease surveillance and how EPS could support that.

They identified many potential ongoing sources of information from swine farms that could help with EPS implementation, such as a collection of treatment, production, and breeding records into swine management software and routine testing for other diseases. They also identified opportunities for further research and development, such as creating ways to streamline necropsies and collect important diagnostic specimens on a more routine basis.

With these ideas in mind, the research team organized a workshop at the 2022 Allen D. Leman Swine Conference, an annual educational event for the global swine industry (The next edition takes place September 16-19, 2023, in St. Paul, Minnesota.)

Bringing together both public and private swine stakeholders, they discussed the potential value of EPS, what improvements in data management would be needed, and the opportunities and challenges facing EPS. Some important concerns were raised, such as labour and cost, but strengths were also identified, like using EPS to support control of PRRS and other diseases, helping to identify suspicious potential ASF cases, and the opportunity to collaborate with initiatives like US SHIP, Secure Pork Supply, and more.

Using this information, the CAHFS team plans to continue developing ways to help swine producers conduct efficient and effective disease surveillance, from fine-tuning their weekly monitoring system to exploring point-of-care tests and precision ag technologies, and more.

Finding and identifying disease is the first step to controlling it. For highly impactful diseases like ASF, every day during an outbreak can make a significant difference in eradicating the disease.

With the continued support of public and private partners, the team at CAHFS hopes to keep supporting swine producers with disease surveillance and protect their herds from ASF.

For more information on this topic, please see our open-source article in Frontiers in Veterinary Science: https://doi.org/10.3389/fvets.2022.1080150.

If you want to learn more about EPS, contribute ideas, or explore a collaboration on improving swine disease surveillance, please contact CAHFS researcher and veterinarian, Dr. Rachel Schambow: scham083@umn.edu . Dr. Schambow and the CAHFS team will gladly provide advice free of charge to veterinarians and producers interested in enhancing their ability to early detect ASF and other foreign diseases of swine.

Dr. Rachel Schambow

Dr. Rachel Schambow is a postdoctoral researcher in the Center for Animal Health and Food Safety (CAHFS) at the University of Minnesota College of Veterinary Medicine. She holds a bachelor’s degree from the University of Wyoming, a DVM from the University of Wisconsin-Madison, and a Ph.D. from the University of Minnesota. Working with Dr. Andres Perez and the CAHFS team, her research focuses on using both qualitative and quantitative epidemiologic tools to support the control of African Swine Fever. Rachel grew up in south-central Wisconsin in a mixed animal veterinary practice and raising and showing Suffolk and Tunis sheep. Throughout her career, she has been interested in public health and epidemiology and is enthusiastic about tackling problems that affect livestock industries.