African Swine Fever
What is it?
African Swine Fever (ASF) is a highly contagious disease of swine, including domesticated hogs, warthogs, European wild boar and American wild (feral) pigs. The virus has the capability to manifest with a wide range of clinical signs and lesions. It can spread very rapidly in pig populations. ASF cannot be differentiated from classical swine fever by either clinical or postmortem examination.
What are the clinical signs?
Mortality rates vary depending on the virulence of the virus. Acute disease has an incubation period of three to seven days, followed by a high fever, and death within 10 days. Hemorrhages primarily occur in lymph nodes, kidneys and heart. Forms of ASF also include a chronic manifestation, which is characterized by emaciation, swollen joints and sometimes respiratory problems. Some pigs develop cyanotic skin blotching, especially on the ears, tail, lower legs or hams.
How is it spread?
There are some areas of the world where ASF is endemic, including countries of sub-Saharan Africa. It is also found in areas of Asia, Europe, Russia, and most recently, China and Vietnam. The virus is found in all body fluids and tissues. Pigs become infected by direct contact with infected pigs or by ingestion of unprocessed infected pig meat or products, including frozen meats. Biting flies, ticks, contaminated farms, and fomites can also spread the virus.
What are details about the virus?
The virus which causes ASF is classified as the only member of a family called African swine fever-like viruses, Asfarviridae. There are distinct genotypes of ASF virus. The virus is highly resistant to a wide pH range, and to the freeze/thaw cycle. The virus can remain infectious for many months at room temperature. Virus in body fluids and serum is inactivated in 30 minutes at 140°F; virus in infected pig meat can remain viable for several weeks to months.
How can it be controlled?
There is no treatment for ASF, and no vaccine. Successful eradication involves rapid diagnosis, slaughter and disposal of all animals on an infected farm.
How is it diagnosed?
The University of Minnesota Veterinary Diagnostic Laboratory is an ASF-approved testing laboratory. The test for ASF is run on whole blood samples, tonsil, spleen and lymph nodes. As with other reportable diseases, the USDA’s National Veterinary Services Laboratory is the nation’s confirmatory lab.
Is there a human health risk?
ASF affects members of the pig family, it is not known to be a human health risk.
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