Although Eradicated, Still A Threat
Program Aid No. 1220 U.S. Department of Agriculture
Hog Cholera: Although Eradicated,
Still A Threat
Hog cholera is an acute, highly contagious, frequently
fatal viral disease of swine. The disease, first recog-
nized in the United States in 1833, resulted for many
years in annual losses of up to $50 million. Only
swine are naturally susceptible to hog cholera; the
disease is not a health hazard to man. Although
clinically similar to African swine fever, hog cholera is
caused by a distinctly different virus.
How It Spreads:
The most common method of spread of hog cholera
is by direct contact between infected and susceptible
swine. Hog cholera also can be spread indirectly when
susceptible pigs come in contact with the body
secretions from infected pigs; when susceptible animals
come in contact with contaminated pens and vehicles;
and when flies, birds, other animals, and some parasites
mechanically carry the virus from infected to susceptible
swine. In rare cases, an infected sow may pass the virus
to her unborn babies. Indirect transmission can happen
when hogs are fed raw or improperly cooked garbage
with pork scraps containing hog cholera virus.
The clinical features of hog cholera vary with the
severity of the infection. A highly virulent strain may
affect susceptible pigs of all ages, producing high body
temperatures and killing over 90 percent of those
infected from 5 to 19 days after initial exposure.
Viruses with low virulence produce milder clinical
illness with lower body temperatures and lower death
losses. Pigs with chronic hog cholera often live to
become stunted pigs, or runts. A few cases may occur in
which pigs appear normal but carry the virus and can
spread it to other susceptible pigs.
Pigs seldom show signs of hog cholera until 4 to 7
days after they become infected. With low virulent or
chronic hog cholera, the incubation period can be much
If your pigs show any of the following signs, you
should suspect hog cholera and call a veterinarian to
confirm the diagnosis:
* Body temperature over 1040 F (420 C); 1020 F
(400 C) is normal.
* No interest in food.
* Unusually slow and inactive; lie piled together.
* Gaunt in appearance.
* Sticky eye discharge.
* Constipation at first-later diarrhea and occasionally
Pigs tend to huddle together as if cold when infected with hog
Affected pigs may be weak and wobbly and may sit
Affected hog showing rough hair coat and dejected appearance.
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* Red areas on skin of ears, abdomen, or legs (most
apparent on white hogs).
Weakness, trembling, inability to stand.
Weak, abnormal, or dead piglets.
Unusual illness or high death losses at weaning time
or other stress periods.
Chronically ill animals.
Secondary infection can confuse the clinical picture, so
these signs may not always be clear.
The most common post-mortem findings are hemorrhage
in the kidneys, lymph nodes, urinary bladder, skin,
larynx, lungs, and large intestines. Pinpoint hemorrhages
are common on the kidneys; the spleen develops wedge-
shaped infarcts (areas of dead tissue); button ulcers may
be found in the intestines; and the lymph nodes and
skin may be congested and hemorrhagic.
Confusion With Other Diseases:
Some of the signs of hog cholera may be similar to
those of domestic swine diseases such as swine erysipelas,
acute salmonellosis, pasteurellosis, and streptococcosis.
Because of this, rapid laboratory assistance in diagnosing
hog cholera is vital. Hog cholera should be suspected
until it is either confirmed or ruled out by identifying
another disease as the cause of illness.
If you suspect hog cholera, call your local veterinarian
or State or Federal animal health official immediately.
A trained veterinarian will be sent to look at your hogs
free of charge to determine if hog cholera is the disease
problem. Any delay in diagnosing hog cholera could be
very costly to the U.S. swine industry.
The reappearance of hog cholera in an area could
* Feeding improperly cooked garbage containing pork
scraps from swine infected with hog cholera virus.
* Introducing infected swine, or their products, from
Outbreaks since 1972 show how quickly hog cholera
can spread when the virus is introduced into swine
markets. The complex commercial movements of swine
and their products in the United States makes prompt
diagnosis and eradication of hog cholera vital. Infected
animals can "shed" the virus several days before illness
is noticed, which points up the need to isolate herds
with hog-cholera-suspect pigs until a diagnosis is made.
The United States was declared free of hog cholera
in 1978 following a 15-year eradication campaign, but
hog cholera exists in many countries with which the
United States trades. So animal health officials enforce
strict import regulations to keep hog cholera out of the
United States and maintain an extensive national
surveillance program to quickly detect introduced
How You Can Help:
Your interest in reading this brochure is the first step
in helping to keep the United States free of hog cholera.
The second step is regular observation of your swine
for any changes in appearance, appetite, or behavior.
In addition, you should:
* Cook or treat all garbage fed to swine to destroy
any hog cholera virus.
* Make sure your hogs have no contact with hogs you
are not sure are healthy.
* Isolate newly purchased pigs for 21 days.
* Practice good sanitation and fly control.
* Avoid visiting other hog farms.
* Make sure vehicles and footwear are disinfected
before allowing them on your farm.
* Check all animals daily for signs of illness.
* Isolate sick pigs until the cause of illness is determined.
* Report sick pigs promptly to your veterinarian or to
State or Federal animal health officials.
Your best insurance is to "think hog cholera" when
confronting a disease in swine involving fever, loss of
appetite, loss of coordination, small or abnormal litters,
or unusual illness or death loss at weaning.
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are common signs of hog cholera.
Pinpoint hemorrhages on the kidneys are characteristic.
Raised, darkened areas on bhe spleen called "infarcts"
"Bullon" ulcers on the lining of the intestine.
Animal and Plant Health Inspection Service
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