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African Swine Fever: United States Department of Agriculture
Animal and Plant Health Inspection Service
Program Aid 1614
African Swine
Fever:
A ForeignThreat to
U.S. Hogs
The U.S. Department of Agriculture (USDA) prohibits discrimi-
nation in all its programs and activities on the basis of race,
color, national origin, age, disability, and where applicable, sex,
marital status, familial status, parental status, religion, sexual
orientation, genetic information, political beliefs, reprisal, or
because all or part of an individuals income is derived from any
public assistance program. (Not all prohibited bases apply to
all programs.) Persons with disabilities who require alternative
means for communication of program information (Braille, large
print, audiotape, etc.) should contact USDAs TARGET Center
at (202) 7202600 (voice and TDD). To file a complaint of
discrimination, write to USDA, Director, Office of Civil Rights,
1400 Independence Avenue, S.W., Washington, D.C. 20250
9410, or call (800) 7953272 (voice) or (202) 7206382 (TDD).
USDA is an equal opportunity provider and employer.
Photo credits: The larger image of healthy pigs on the cover
was taken by USDAAgricultural Research Service photogra-
pher Keith Weller. The smaller cover shot comes from the
APHIS photo library. The source for images inside the leaflet
has been given in captions wherever possible. Uncredited
images are from the APHIS photo library.
Revised March 2006 Lymph nodeshemorrhages may be minute and
diffused, or entire nodes may resemble blood clots; Kidneyhemorrhage ranges from pinpoint to entire
organ; and Spleenmay be enlarged up to twice its normal size.
Excessive fluid may be present in body cavities and
joints. Occasionally, death is sudden and no obvious
lesions are found.
Hogs dying from the milder, chronic strains may also
have secondary infections, which complicate the clinical
and postmortem picture.
As milder forms emerge, it is becoming more difficult to
distinguish between ASF and other swine diseases at
necropsy.
How Does ASF Spread?
ASF spreads rapidly in both acute and chronic forms.
Infected pigs are a primary source of the disease.
During the acute disease, the ASF virus exists in all
excretions and secretions of an infected pig and can
survive outside of its host for long periods. Meat from
infected pigs can harbor the virus up to 150 days.
In Africa, wild pigs are carriers of the ASF virus.
Although they show no clinical signs of illness, infected
warthogs and wild bush pigs can transmit the disease to
domestic swine.
ASF can be spread by: Contact between infected and healthy pigs; Carrier animals; Contaminated garbage, feed, or water; Infected ticks
(Ornithodorus spp.); Contaminated premises, clothing, footwear, or
equipment; Contaminated vehicles; or Improper disposal of infected carcasses.
Certain
Ornithodorus ticks can be natural hosts of ASF
and are capable of transmitting the virus from one
generation to the next. Thus, ticks on farms with ASF-
infected pigs may carry the virus for longer than 6
months and could infect reintroduced swine. The virus is
highly resistant to some chemical disinfectants but is
quite sensitive to temperatures greater than 97.5
°F
(37
°C).
Many outbreaks have been traced directly to
uncooked garbage fed to hogs.
What Are the U.S. Prevention Measures?
To prevent the introduction of ASF into the United States,
the U.S. Department of Agriculture (USDA) prohibits the
importation of live hogs and uncooked pork from any
country where ASF exists. Pork products from those
countries can enter the United States under two condi-
tions: (1) the product must be commercially canned,
hermetically sealed, and fully sterilized so it remains
shelf stable without refrigeration; and (2) the processes
used have been proven to inactivate the virus. Strict
quarantine and inspection practices are required at U.S.
ports-of-entry.
Recognizing the threat that ASF constitutes for the
United States and the rest of the Western Hemisphere,
USDAs Animal and Plant Health Inspection Service
(APHIS) has worked with countries that have suffered
outbreaks. When an ASF outbreak occurred in the
Dominican Republic in 1978, APHIS supported the
countrys eradication and repopulation program. By
September 1980, all domestic pigs had been slaugh-
tered. APHIS was also actively involved in the eradica-
tion and repopulation project in Haiti after the ASF
outbreak there in 1979.
What Can You Do?
You can support U.S. efforts against ASF by

Establishing good biosecurity practices on your
farm; Watching your herds and being alert to abnormal
conditions and reporting them to your veterinarian; Isolating hogs showing signs of disease and not
moving them from your premises; Restricting movement of all livestock on your
premises if you suspect an outbreak; and Restricting movement of persons, vehicles, and
equipment to and from your premises until you are
notified of the diagnosis.
Report Suspicious Cases
Veterinarians and livestock owners who suspect an
animal may have ASF or any other foreign animal
disease should immediately contact State or Federal
animal health officials.
For more information, contact
USDA, APHIS, Veterinary Services
Emergency Management
4700 River Road, Unit 41
Riverdale, MD 207371231
Telephone (301) 7348073
Fax (301) 7347817
Current information on animal diseases and suspected
outbreaks is also available on the Internet. To reach the
APHIS home page, point your Web browser to http://
www.aphis.usda.gov and select the Hot Issues button
for outbreak information.
Practicing good
biosecurity by
disinfecting clothing,
footwear, equipment,
and vehicles will help
prevent the spread of
ASF.
(APHIS photo
by R. Anson Eaglin.) African swine fever is a highly fatal disease
that can kill almost all pigs that become
infected.
Reddening of the ears is a typical sign of ASF.
What Is African Swine Fever?
African swine fever (ASF) is one of the most destructive
diseases of pigs worldwide. ASF is a contagious, often
fatal viral disease of swine. The acute forms are charac-
terized by high fever, reddening of the skin, pronounced
hemorrhages in lymph nodes and internal organs, and,
occasionally, enlargement of the spleen. The disease
does not affect people or animals outside the pig family.
Ticks often carry the virus that causes ASF from infected
swine to healthy animals.
Since the 1960s, subacute and chronic forms of ASF as
well as mild or inapparent infections have been increas-
ingly reported. Because of their low mortality rates,
these forms of ASF make it difficult to recognize,
especially in a country where the disease has entered
for the first time and farmers and veterinarians have had
no previous experience with it.
Several other swine diseases have clinical signs and
gross lesions similar to those caused by ASF. Classical
swine fever (hog cholera), salmonellosis, and ASF are
virtually impossible to distinguish from one another in the
field. Laboratory confirmation is required to tell these
diseases apart.
Unfortunately, no effective vaccine or treatment exists for
ASF. The drastic measure of depopulation of affected
and exposed swine must be applied to control or
eradicate it in most situations.
Where Does ASF Occur?
ASF has existed for many years in Africa as an inappar-
ent infection in warthogs, bush pigs, and giant forest
hogs. It was recognized as a disease when it was
contracted by domestic pigs of European origin in Kenya
in 1909. ASF is also a very important clinical disease of
domestic pigs in sub-Saharan Africa.
The global threat of ASF became apparent when it
appeared in Portugal in 1957. This first incursion was
eradicated in 1958 after 6,103 pigs died of the disease
and 10,354 more were slaughtered. Outbreaks occur-
ring along the Spanish border in France in 1964, 1967,
and 1974 were eradicated by slaughtering infected and
exposed animals. Since the mid-1960s, outbreaks have
occurred in Italy, Spain, Malta, Sardinia, Belgium, and
the Netherlands. Except for Sardinia, Europe is free of
ASF today.
In the Western Hemisphere, ASF first appeared in Cuba
in 1971. The disease was eradicated but only after more
than 400,000 pigs died or were slaughtered. In the late
1970s, ASF entered Brazil, the Dominican Republic,
Haiti, and, again, Cuba. The disease was eradicated
from the Western Hemisphere by depopulation.
What Are the Clinical Signs of ASF?
The incubation period for ASF is 5 to 15 days. The
highly virulent form of the disease can kill pigs before
they show any apparent clinical signs of illness.
Reduced appetite is often the first sign of ASF, and some
pigs have a high fever. But most often, dead pigs are the
first indication of the disease seen by producers. Hogs
that recover from ASF can still transmit the virus for a
long time.
An infected pig experiences a sharp rise in temperature,
from normal 101
°F (38.3 °C) to 105 °F (40.6 °C) or
higher. An animals skin may appear reddened as a
result of fever.
Pigs suffering from