African Swine Fever: One of the Big Three is Spreading

African Swine Fever (ASF) is a viral disease that causes high mortality in domestic and wild pigs. It, along with Classical Swine Fever and Foot and Mouth Disease, is one of the Big Three highly transmissible diseases that would stop our export markets cold if identified in the United States or Canada.

There is no vaccine for ASF and due to the complexity of the virus and the difficulty in identifying the protective proteins of the virus, no vaccine is anticipated in the near future.

African Swine Fever spreads through close contact with infected animals or their excretions, or through feeding uncooked contaminated meat to susceptible pigs. In Africa, it is also spread by warthogs and other native pigs that do not show clinical signs of the disease, as well as by soft bodied ticks. ASF is very hardy in the environment. ASF virus does not infect other animals or humans, there are no food safety implications. There is no vaccine for ASF.

While strains of ASF may vary in their virulence, in most cases ASF causes severe illness and high mortality rates in pigs of all ages. Pigs will exhibit high fever, decreased appetite and reluctance to move. Skin may be red, blotchy or have bloody/black lesions on the ears, tail and lower limbs. They may also have diarrhea, abortion, or respiratory signs. Upon necropsy the spleen is enlarged and friable, lymph nodes will be black and enlarged, and blood may be observed throughout the body cavities.

There is no vaccine for ASF and due to the complexity of the virus and the difficulty in identifying the protective proteins of the virus, no vaccine is anticipated in the near future.


ASF had been largely eliminated from most of the world, except for Africa, prior to 2007. In 2007 an outbreak was identified in the Caucuses region of Georgia. The disease spread through wild boar movements and illegal movements of meat across Russia and many of the Eastern European and Baltic nations.

On August 3, 2018 it was reported that China had its first case of African Swine Fever. The sequence of the Chinese virus is very similar to the virus found in Georgia, Russia and Europe. Since then the disease has spread widely in China.

African Swine Fever Outbreak map Chinese provinces as of April 9, 2019

African Swine Fever Outbreak table Chinese Provinces as of April 9, 2019


There are several potential vehicles that could carry the ASF virus to the United States (or Canada). These include: international travelers that would have either contaminated footwear/clothing or be carrying infected meat products, importation of contaminated meat products, and importation of contaminated feed ingredients. In each of these cases the contaminated article would need to either contact or be fed to, susceptible pigs.

We know from work done by Dr. Scott Dee, et al, that some virus contained in certain feed ingredients can survive a simulated transport model. The chart above shows which of the feedstuffs tested could support survival of various viruses. There are other imported products that were not tested in this model that may potentially support virus survival. Further research by Niederwerder, et al has now demonstrated that the risk of ASF transmission through feed increases with multiple feedings and is more efficient in liquid than in dry ingredients.

These researchers have also been involved in research to determine the half life of virus in feed ingredients to help in the calculation of holding times that would inactivate 99.99% of virus in an ingredient. More information on all these studies, as well as information sheets on holding times and questions for producers to ask of their feed suppliers can be accessed at http://nppc.org/asf/ or at www.swinehealth.org

Summary of afrian swine fever virus survival from batch 4 samples (37 DPI or 30 DPI) arcoss both models


National Pork Producer Council (NPPC), the National Pork Board (NPB), the Swine Health Information Center (SHIC) and the American Association of Swine Veterinarians (AASV) have been in close contact with the United States Department of Agriculture (USDA) and Customs and Border Protection (CBP) to discuss ways to prevent ASF from entering the United States. The organizations developed a list of potential actions for prevention, and if needed, response to an ASF outbreak.

The industry organizations and USDA are committed to open and timely communication on this situation and the potential for increased protective actions. The USDA has a Risk Identification Unit that monitors the disease situation globally and evaluates changes in risk status. The Risk Identification Unit is in the process of developing a qualitative risk assessment looking at potential entry points of the virus into the U.S. so that potential gaps in protection can be identified and addressed.

USDA prohibits the import of fresh meat from ASF positive zones (including entire countries that do not have recognized zones or regionalization), and industry has worked closely with USDA to understand the European ASF zoning and regionalization. USDA also prohibits the import of live animals from ASF positive zones.

Customs and Border Protection (CBP) has enhanced inspections of passengers/luggage on planes arriving from China and Russia, as well as other Eastern European locations. Targeting of other flights based on the origination country of passengers is also a tool utilized by CBP. The most visible tool is the Beagle Brigade, but the canine teams are one of many steps taken by CBP to prevent the entry of dangerous products into the country.

The industry organizations have worked closely with USDA for over a year to validate foreign animal disease (including ASF) testing using oral fluids. At the beginning of the Chinese outbreak whole blood was the validated sample for ASAF testing in the National Animal Health Laboratory Network (NAHLN) laboratories, which are most of the state veterinary diagnostic laboratories. USDA has now also validated spleen and lymph node for use by the NAHLN laboratories during a foreign animal disease investigation. USDA has conducted an evaluation of laboratory capacity to test for ASF.

The Swine Health Information Center (SHIC) has funded projects that are underway to evaluate mitigations to neutralize the virus in feed ingredients. SHIC has also funded projects to develop validated sampling methods for testing feed ingredients for viral contamination. Also, currently being researched are feed pathogen mitigation options including: Feed additives, component holding time and temperature before processing, Hazard Analysis and Risk-Based Preventive Controls, and blockchain are being investigated with urgency. Available results can be accessed at SwineHealth.org.

Since feeding uncooked or undercooked infected meat to pigs is a known pathway for ASF transmission, NPPC has asked USDA to increase their compliance inspections for licensed waste feeders and searches for non-licensed waste feeding facilities.

A series of ASF-specific emergency response exercises are being conducted with allied industry, NAHLN and state and federal animal health officials participating. The first one was held in December 2018 with further exercises scheduled throughout 2019. Coordination of response and communication plans with Canada and Mexico is underway.


With the best information currently available, and until we learn more, we recommend extreme caution if considering hosting someone from an ASF positive region of the world on US farms. If visitors are hosted, the USDA Foreign Animal Disease Diagnostic Laboratory on Plum Island recommends a 5-day downtime for anyone planning to have contact with susceptible species after working with diseases and animals on the island.

Producers should review their biosecurity protocols. If producers have workers from ASF positive regions, they should also review their down time policies for workers returning from visits home. It must be stressed to such workers that they are not allowed to bring meat from their home country into the United States or the farm.

Producers should fill out the Foreign Animal Disease Preparation Checklist found at https://library.pork.org/media/?mediaId=FD08BB0E-C446-4433-8D722BF983B30B1C. Additionally, producers should consider enrolling in the Secure Pork Supply program at www.SecurePork.org.

Producers should consider visiting with their feed suppliers to ascertain the origin of the feed ingredients they are using in their diets. Below is a list of questions they should consider asking:

  1. Describe the facility’s biosecurity program to minimize the spread of pathogens from people, vehicles and ingredients.
  2. Describe the facility’s employee training on feed safety.
  3. Describe the facility’s pest control program.
  4. Describe the facility’s traceability program.
  5. Describe the facility’s supplier approval program.
  6. Is the facility certified by a third-party certification body for food safety? Third-party certification programs may include the Feed Additives Manufacturers (FAMI-QS), the International Organization for Standardization (ISO), the Safe Quality Food (SQF), Safe Feed/Safe Food, etc.
  7. Does the facility utilize ingredients that were manufactured or packaged outside of the United States?


In summary, the industry is working closely with USDA to prioritize preventing ASF from entering the U.S. swine herd and, in the case of an ASF outbreak, being prepared to respond.

Dr. Liz Wagstrom
Dr. Liz Wagstrom is recognized as an expert on pig health, food safety and public health. Dr. Wagstrom has a wealth of experience in production agriculture and public health as a result of her 9 years with the US National Pork Board, first as Director of Veterinary Services and later as Assistant Vice President for Science and Technology. Following a stint as the Director of the Public Practice Residency program at the University of Minnesota’s College of Veterinary Medicine she joined the National Pork Producers Council as the Chief Veterinarian in 2011. She has also held positions within a state department of health and with a major swine production company. She holds a Doctor of Veterinary Medicine Degree, a Masters in Veterinary Preventive Medicine from Iowa State University and she is board certified by the American College of Veterinary Preventive Medicine.