Updates on African Swine Fever

*Updated March, 2023.

African swine fever (ASF) has the potential to destroy the U. S. pork industry by killing millions of pigs if it enters the country. A study from Iowa State University projected that if ASF spread to the United States and was not controlled within two years, the pork industry would lose $50 billion over ten years. Even in the best case scenario of the disease being controlled within two years, the projected losses are $15 billion (Carriquiry et al., 2020). In 2019, one fourth of the world’s pigs—about 440 million of them—died because of ASF outbreaks (Mackenzie, 2019). ASF does not infect humans, but it is responsible for global trade bans and the culling of infected herds due to its severity, resistance to disinfectants and adaptability to live in the environment (Iowa State University, 2018).

Although ASF has never been found in the United States, researchers are looking into options for managing the disease if an outbreak does occur. Currently, there is no vaccine available for ASF, but hope may be on the horizon. Scientists from the Pirbright Institute tested a new vaccine that reportedly protected all the pigs from ASF in one study (Goatley et al., 2020). Until a vaccine is commercially available, biosecurity practices nationwide and on the farm are our best defense against ASF.

ASF Transmission Pathways

Two different tick vectors for the disease have been identified: one species in Spain and Portugal and another species in Africa (Costard et al., 2013). Besides these tick vectors, ASF is transmitted to previously uninfected pigs via the consumption of contaminated, under-cooked pork mixed in their feed. The virus can then be passed between pigs via direct contact and contact with body fluids such as blood and urine (USAHA, 2008). Because of the virus’s resilience in the environment, it can also be transmitted from infected herds to new herds via contaminated vehicles, clothing and other human articles (USDA, 2018).

What are the Symptoms of ASF?

To be proactive, pork producers in the United States should be familiar with the symptoms of ASF, which include the following (Oura, 2013):

• Loss of appetite, lethargy
• Vomiting
• Respiratory distress
• Bleeding from the nose/rectum
• Diarrhea
• Abortion

ASF can have varying clinical signs and virulence or severity. In chronic instances of ASF, symptoms persist for a longer period and are less severe. Acute cases are those where sudden death occurs without many clinical signs. However, even in acute outbreaks, symptoms may present themselves generically, resulting in the animals’ conditions worsening or deaths before the cause is identified (Iowa State University, 2019).

Preventing ASF in the U.S.

Currently, prevention is the best defense against ASF. One important biosecurity protocol for pork producers is the use of disinfectants. Due to the adaptability of ASF, not every disinfectant effectively kills the virus, so pork producers must be sure they are using appropriate disinfectants (Juszkiewicz et al., 2019). Producers should reference the list of EPA-Approved Pesticides for ones that are effective against ASF. Some disinfectants that have been proven to work against ASF are those containing 1% formaldehyde or sodium hypochlorite, among others (Juszkiewicz et al., 2019).

Other biosecurity measures include:

• Management of wild pig populations, as they can transmit ASF to domesticated populations.
• Appropriate waste disposal.
• Managing pork imports (OIE, 2018).

In northeast Europe, ASF exists in wild boar populations without tick or domestic pig vectors. This makes managing their populations important in preventing ASF from spreading to new locations and to domestic swine (FAO). This is relevant to the United States because at least 35 different states have feral pigs, with a population of about 6 million animals (USDA APHIS, 2020). Thus, preventing ASF in the United States involves monitoring feral swine populations and their exposure to foreign animal diseases (FADs). It is also important to reference the USDA’s Carcass Management Considerations when disposing of infected animal carcasses or suspect animals. Responsible carcass management is important because ASF can persist in the environment, and scavengers can spread the disease from infected carcasses to other swine (FAO).

When traveling to the United States, travelers should “declare all meats, animals, and animal products” to U.S. Customs & Border Patrol, as well as informing them if they have “been on a farm, or near livestock or wild pigs” (U.S. Customs & Border Protection). As outlined in Healthy Farm Healthy Agriculture website’s Detect section, emerging and foreign disease observation is key in order to recognize FADs to prevent outbreaks.

According to the USDA APHIS ASF Response Strategy, rapid detection and management of ASF if it spread to the United States would be vital in minimizing the number of infected pigs and for protecting the food supply. By quickly isolating and culling infected herds, a potential outbreak could be contained before it spread to other farms. The goal is to enable the United States to “regain ASF-free status without the response effort causing more disruption and damage than the outbreak itself,” in the event of an outbreak (FAD PReP, 2019).

Stay Updated on ASF

Swine producers – the Pork Checkoff/National Pork Board website maintains current ASF and other foreign animal disease information on their website. Visit the site at https://www.pork.org/production/animal-disease/foreign-animal-disease-resources/.

Producers and veterinarians – the USDA NIFA website Protect Our Pigs contains current information on ASF, including international and regulatory updates. Visit the site at https://www.aphis.usda.gov/aphis/resources/pests-diseases/asf/asf

References

Carriquiry, M., Elobeid, A., Swenson, D. A., & Hayes, D. J. (2020). CARD @ Iowa State University. Retrieved from https://www.card.iastate.edu/products/publications/synopsis/?p=1300

Center for Food Security & Public Health Iowa State University (2018). African Swine Fever FastFacts [PDF]. Retrieved from http://www.cfsph.iastate.edu/FastFacts/pdfs/african_swine_fever_F.pdf

Committee on Foreign and Emerging Diseases of the United States Animal Health Association (2008). Foreign Animal Diseases Seventh Edition [PDF]. Retrieved from https://www.aphis.usda.gov/emergency_response/downloads/nahems/fad.pdf

Costard S, Jones BA, Martínez-López B, Mur L, de la Torre A, Martínez M, et al. (2013). Introduction of African Swine Fever into the European Union through Illegal Importation of Pork and Pork Products. PLoS ONE 8(4): e61104. https://doi.org/10.1371/journal.pone.0061104

Goatley, L. C., Reis, A. L., Portugal, R., Goldswain, H., Shimmon, G. L., Hargreaves, Z., Ho, C.-S., et al. (2020). A Pool of Eight Virally Vectored African Swine Fever Antigens Protect Pigs against Fatal Disease. Vaccines, 8(2), 234. MDPI AG. http://dx.doi.org/10.3390/vaccines8020234

Iowa State University (2019). African Swine Fever [PDF]. Retrieved from http://www.cfsph.iastate.edu/Factsheets/pdfs/african_swine_fever.pdf

Juszkiewicz M, Walczak M, Woźniakowski G. (2019). Characteristics of Selected Active Substances used in Disinfectants and their Virucidal Activity Against ASFV. J Vet Res., 63(1), 17-25. https://pubmed.ncbi.nlm.nih.gov/30989131/

Mackenzie, D. (2019). A quarter of all pigs have died this year due to African swine fever. NewScientist. Retrieved from https://www.newscientist.com/article/2222501-a-quarter-of-all-pigs-have-died-this-year-due-to-african-swine-fever/

World Organisation for Animal Health (2018). African swine fever. Retrieved from https://www.woah.org/en/disease/african-swine-fever/

Oura, C. (2013). Overview of African Swine Fever – Generalized Conditions. Merck Veterinary Manual. Retrieved from https://www.merckvetmanual.com/generalized-conditions/african-swine-fever/overview-of-african-swine-fever

Perez, S., Brihn, A., & Perez, A. (2020). Swine Disease Global Surveillance Report [PDF]. University of Minnesota. Retrieved from https://www.swinehealth.org/wp-content/uploads/2020/06/SHIC-109-GSDMR-6-3-2020.pdf

The Pork Checkoff. (n.d.). African Swine Fever & Foreign Animal Disease Resources. Retrieved from https://www.pork.org/production/animal-disease/foreign-animal-disease-resources/

U.S. Customs and Border Protection. (n.d.). African Swine Fever FAQs. Retrieved from https://www.cbp.gov/travel/international-visitors/agricultural-items/african-swine-fever-faqs

U.S. Department of Agriculture (2019). ASF Response [PDF]. Retrieved from https://www.aphis.usda.gov/animal_health/carcass/docs/asf-3d-summary-guidance.pdf

U.S. Department of Agriculture (2020). Poland’s Third Commercial ASF Outbreak in 2020. Retrieved from https://www.fas.usda.gov/data/poland-polands-third-commercial-asf-outbreak-2020

U.S. Department of Agriculture, Animal and Plant Health Inspection Services (2018). Potential Pesticides to Use Against the Causative Agents of Selected Foreign Animal Diseases in Farm Settings [PDF]. Retrieved from https://www.aphis.usda.gov/animal_health/emergency_management/downloads/fad_epa_disinfectants.pdf

U.S. Department of Agriculture, Animal and Plant Health Inspection Service (2020). History of Feral Swine in the Americas. Retrieved from https://www.aphis.usda.gov/aphis/resources/pests-diseases/feral-swine/sa-fs-history

U.S. Department of Agriculture, Animal and Plant Health Inspection Services (2019). The Foreign Animal Disease Preparedness and Response Plan (FAD PReP)—Disease Response Strategy: African Swine Fever [PDF]. Retrieved from https://www.aphis.usda.gov/animal_health/emergency_management/downloads/asf_strategies.pdf

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About the Author
Kortnie Wheaton
Kortnie Wheaton was an undergraduate student at the University of Vermont studying for a Bachelor of Science in Animal Science. She was on the pre-veterinary track and applying to veterinary school. She was part of the UVM CREAM 2020 class, and her experiences have made her want to pursue farm animal medicine in veterinary school. During the summer of 2020, Kortnie milked water buffalo at a small dairy farm near her home in Landis, North Carolina. In her free time, Kortnie likes to experiment with nature photography and hike with her dogs.

About the Editor
Joanna Cummings
Cummings received a bachelor of science degree in horticulture from The Pennsylvania State University, with a specialization in vegetable crop and greenhouse production. At PSU, she was a research technician on no-tillage vegetable crop experiments, and a greenhouse assistant in the All-American Selections Research Gardens. Her career in the agriculture industry includes field research, work with dairy and vegetable farms, and as a greenhouse manager, estate gardener, landscaper and market garden entrepreneur. She transitioned to the science communication field after receiving a master of science degree in environmental communications from Antioch University New England. At Antioch, she was a field botany laboratory teaching assistant and manager of the herbarium.
She works with Research Associate Professor Julie M. Smith as a communications professional in the University of Vermont Animal and Veterinary Sciences Department. She is the webmaster for the Healthy Farms Healthy Agriculture website.

About the Editor
Dr. Julie Smith
Dr. Julie Smith is a research associate professor at the University of Vermont. Julie received her B.S. in Biological Sciences, D.V.M., and Ph.D. in Animal Nutrition at Cornell University. Since 2002, she has applied her veterinary background to programs in the areas of herd health, calf and heifer management, and agricultural emergency management. She has taught Animal Welfare, Calf Biology and Management, and ABCs of Biosecurity to undergraduates, mostly in the Department of Animal and Veterinary Sciences. 
As a veterinarian and spouse of a dairy farmer, Julie is well aware of the animal health and well-being concerns of dairy animals. Julie has conducted trainings for Extension educators, livestock producers, and community members on the risks posed by a range of animal diseases, whether they already exist in the United States, exist outside of the United States, or pose a risk to both animal and human health. In all cases, she emphasizes the importance of awareness and prevention. In addition, she has led a number of projects on biosecurity and emergency disease preparedness.