Preparing for African Swine Fever in the U.S.
As African Swine Fever (ASF) is currently spreading across China, the greatest concerns are the range that the disease has traveled across the country in just a short amount of time. Our greatest defense as a state is to encourage producers and auction houses to actively work with veterinarians and establish communication with the state veterinary services now, while the disease is not knocking on our door step.
This article provides a timeline of out breaks as of August 23rd, 2018, and some tips to keeping your herd and the U.S. pork supply safe from ASF and other foreign animal diseases.
In all of the cases reported so far, DNA testing and PCR sequencing of viral genome has been utilized to determine the most likely origin of the disease. The current solution within China appears to be to isolate through establishing transport blockades and to ‘stamp out’ the disease through euthanasia and disposal. No infected hogs have been reported as slaughtered.
- March 2017 - Backyard farm outbreak, Irkutsk region near Mongolia
- 40 pigs died within 6 days of first clinical signs. Thought that pigs were fed contaminated pork table scraps. This is thought to be the most common route of infection in backyard herds.
- October 2017 - Several outbreaks continue to occur in Siberia from the initial outbreak in March 2017
- Genotyping of ASF strain from MArch 2017 is a highly virulent strain. Numerous outbreaks creep closer to Chinese boarder. Contaminated pork products continue to be considered the most common source of spread of ASF, particularly considering the distance between Siberian outbreak and closest Russian source of ASF (>4,000 km or 2485)
- August 3, 2018 - First reported case of ASF in People's Republic of China, Liaoning
- 8792 swine considered susceptible, with 47 cases and 47 deaths reported (100% mortality). The remaining herd was killed and disposed of, indicating a full loss. Follow up report on August 16th indicated that all live pigs in two villages within the threatened area were 'stamped out', presumably killed and disposed of as they continue to work and prevent further spread.
- August 16, 2018 - Second reported case of ASF in People's Republic of China, Henan
- 260 swine considered susceptible, 30 cases and 30 deaths (100% mortality), and the remaining herd killed and disposed (230). Case is considered on going. These infected pigs were reported to have been legally transported from a live market in China.
- August 19, 2018 - Third Reported case of ASF in People's Republic of China, Jiangsu
- 615 swine considered susceptible, with 88 reported deaths and 527 animals killed and disposed. This case in considered on going.
- August 23, 2018 - Fourth reported outbreak in People's Republic of China, Zhejiang
- 430 swine considered susceptible, with 79% mortality. 90 remaining hogs euthanized and disposed. Case is ongoing
How is it spread?
Most infections are spread through direct contact between infected and naïve swine populations, of the outbreaks in China, at least one has been sourced to the legal purchase of pigs from a live hog market. In Serbia, it was determined that feeding contaminated pork products to backyard pigs has lead to the spread of disease across long distances. African swine fever is also the only known DNA virus that utilizes the sylvatic cycle (an insect vector within the virus lifecycle) to facilitate transmission of the virus between ticks and hogs, which has been observed in African warthogs and in the Eurasian wild boar population. This cycle can also occur in domestic pig production systems, however, once the virus has been introduced into a swine herd, via tick or live animal the virus is capable of spreading via direct and indirect contact with other pigs. Indirect contact includes traveling on pests such as rodents and birds that can carry infected ticks.
What does it look like?
Clinical signs and symptoms are indicated to vary, possibly making diagnosis tricky. The greatest concerns for this virus are the sudden high rate of mortality (near 100%) and often few symptoms observed prior to sudden death. Necropsy after sudden death of swine is encouraged to look for possible internal signs of ASF infection. Infections that do not result in sudden death will result in fever and internal lesions. Wild pigs have been observed to be infected with the disease and show no symptoms, causing further difficulty in diagnosis. The only way to know if you have swine carrying ASF is to have them tested by your veterinarian.
Can it be treated?
At this time, there are no approved vaccines or treatments for ASF.
How might this affect U.S. pork producers?
While there is currently no surveillance program for ASF in the U.S., the possibility for spread of this disease is ever present. This evidence of spread associated infections traveling over thousands of miles only emphasizes the need for continued vigilance within the Americas to prevent the further spread of ASF around the world.
This video provides a good summary of the impact to the swine industry as a whole should a positive sample of ASF be found in the U.S. swine population. View an updated video from the National Pork Board.
Preventing ASF infection or spread in swine herds
The greatest task that swine producers can do to prevent ASF at this point in time is to remain vigilant in practicing biosecurity in your herd. Communicate with veterinarians, be diligent when purchasing swine, and take advantage of the premises ID programs offered by the state and national organizations. These programs enable producers to participate in state and federal health programs, allowing them to be quickly identified and classified as quarantined or safe if a foreign animal disease outbreak does occur within the U.S.
Keep these items in mind around the housing, expansion, and transport of your herd:
- When purchasing swine, know the source and ask for health certificates.
- Register for premises identification from Pennsylvania Department of Agriculture and on the Secure Pork website
- Observe appropriate quarantine periods
- Create a bio-security protocol and practice it on your farm
- Report suspected illness
- Keep wild swine populations away from domestic swine herds
- Gogin et al., (2013) African swine fever in the North Caucasus region and the Russian Federation in years 2007–2012, Virus Research, Volume 173, Issue 1, 2013, Pages 198-203, ISSN 0168-1702. (Direct link to article)
- Kolbasov. et al. (2018). African Swine Fever Virus, Siberia, Russia, 2017. Emerging Infectious Diseases, 24(4), 796-798.
- World Organization for Animal Health, World Animal Health Information Database (WAHIS Interface) – Version 1. Copyright © World Organisation for Animal Health (OIE). Access date: August 21, 2018.
- Pietschmann et al., (2016). African swine fever virus transmission cycles in Central Europe: Evaluation of wild boar-soft tick contacts through detection of antibodies against Ornithodoros erraticus saliva antigen. BMC Veterinary Research, 12, 1.
- Foreign Animal Disease Preparedness and Response Plan (FAD PReP), Disease Response Strategy: African Swine Fever (2013).