Contagious Bovine Pleuropneumonia
Veterinary Services
October 2003
Contagious bovine pleuropneumonia (CBPP) is a slow–spreading,
infectious disease of cattle, primarily affecting the lungs and joints.
Other than occasional infection in Asian buffalo, no other animals or
humans are susceptible to this disease.
CBPP is endemic in most of Africa, is a problem in parts of Asia, especially
India and China, and has occurred in Europe. CBPP was eradicated from
the United States in 1892. The Bureau of Animal Industry, which was
the forerunner of the U.S. Department of Agriculture’s (USDA)
Animal and Plant Health Inspection Service (APHIS), was formed in 1884
specifically to eradicate CBPP. Currently, CBPP is not present in the
Western Hemisphere.
How it Spreads
Under natural conditions, CBPP spreads directly from infected to susceptible
cattle in close contact with each other. Infected cattle breathe and
cough out droplets of moisture containing Mycoplasma mycoides. The bacteria
are then inhaled by nearby cattle. Exposed cattle, if susceptible, may
develop CBPP and are considered infectious for at least 6 months after
exposure to cattle with the disease.
Cattle vary greatly in their susceptibility to CBPP. Cattle in closely
confined quarters have higher rates of infection than cattle on the
open range due to their close proximity to each other and the increased
chance to breathe in contaminated air droplets exhaled by herdmates.
In typical outbreaks, about 40 percent of exposed cattle get the disease,
and mortality among diseased cattle can range from 10 percent to 70
percent. In one African outbreak, 100,000 cattle died of CBPP in 2 years.
The disease spreads slowly. CBPP is most easily spread in the early
stages of infection. Infected cattle begin to breathe out bacteria during
the incubation period—even before signs develop. Although not
yet substantiated experimentally, it is thought that cattle that recover
from CBPP may harbor a walled–off infection in their lungs; if
stressed, the walls around the infection break down and the animal may
become an active shedder of the organism again, and a source of infection,
potentially showing no signs of disease.
Some cattle can be carriers—infected animals that never develop
typical signs of the disease. Carriers are dangerous because they frequently
introduce the disease into previously uninfected areas. In fact, most
new outbreaks can be traced to a carrier or to a healthy–looking
animal in the incubation stage of CBPP that was moved into a susceptible
population.
Clinical Signs
Cattle are the only animals naturally infected by CBPP. Susceptible
cattle usually develop signs 3 to 6 weeks after they are exposed, but
in highly susceptible cattle, signs may develop within 10 to 14 days.
There are three forms of the disease: acute, peracute, and mild.
Acute form. The acute form of CBPP is the most common and it is frequently
fatal. Surviving animals recover slowly. An infected animal’s
temperature rises suddenly, accompanied by loss of appetite. There is
a drop in milk production in cows.
Breathing becomes rapid and shallow. After exercise, the animal coughs
frequently. At first, the cough is dry, but later becomes moist. As
the disease progresses, the animal shows obvious pain while inhaling
and exhaling. The animal assumes a characteristic stance, with head
lowered, back arched, elbows pointed outward to allow the chest to maximally
expand, and mouth open to ease its breathing.
Usually, the bacteria invade only one lung. As pneumonia and pleurisy
develop, the lung becomes inflamed and enlarged. In fatal cases, air
passages fill up with fluid, the body of the lung becomes firm with
fibrous connective tissue, and is followed by the death of lung tissues.
The animal suffers from lack of air. Fibrous tissues connect the normally
unattached outer surface of the lung to the inner chest wall. Great
quantities of fluid may fill the chest cavity as lung tissues break
down. Then, cattle lose weight, become distressed, and stop chewing
their cud. Edema, or swelling may develop in the throat and dewlap.
Cattle may “go down,” refusing to stand up before they die.
In fatal cases, death comes 2 to 5 weeks after first signs of disease.
Peracute form. The peracute—or severe—form of CBPP is uncommon.
Cattle with this form of the disease develop many of the signs described
for acute infection, or they may develop a severe form of pneumonia.
Death usually comes 1 to 3 weeks after signs appear.
Mild form. A mild—or subclinical—form of CBPP also occurs.
Although cattle do not show signs of disease, they become carriers and
continue to spread CBPP. Normally, this form is not fatal for several
years. Any time an animal with the mild form is under stress, it may
develop signs of the acute form.
Detection
Laboratory and field diagnostic tests have been perfected to detect
CBPP. In countries where the disease exists, diagnosis is based on the
combination of an examination of suspect cattle by a veterinarian, review
of the history of the herd, and a postmortem examination including submission
of samples for essential laboratory tests.
The necropsy examination often reveals characteristic prominent fibrous
tissue in a “marbled” pattern in the affected lung. Large
areas of damaged lung tissue will feel as firm as liver. In some of
the walled–off areas of the lung, tissue will begin to die. A
large quantity of straw–colored fluid is often found in the chest
cavity.
One or more joints of the infected animal may be swollen. The joint
fluid in the affected joint will have lost its normal viscosity and
have a watery consistency.
Prevention and Control
APHIS continues to prohibit imports of live cattle from countries where
CBPP exists. In addition, USDA works closely with U.S. Department of
Homeland Security (USDHS) inspectors stationed at U.S. ports of entry
to ensure that import restrictions are enforced. These measures are
designed to prevent the accidental introduction of a carrier or infected
animal and are described in further detail below.
If CBPP should enter the United States, in spite of the established
safeguarding measures, it would be a major threat to the U.S. cattle
industry.
The following disease–fighting measures have been used against
CBPP:
- On–farm quarantine of suspicious and contact animals
- Slaughter of infected and exposed/contact cattle with proper disposal
of animals and contaminated material
- Extensive cleaning and disinfection of the infected premises, equipment,
and facilities
- Restrictions on the movement of all livestock in the affected area
- Vaccination (only in countries with endemic CBPP)
The Animal and Plant Health Inspection Service’s Role
USDA has emergency response plans in place to deal quickly with the
accidental or intentional introduction of this and other foreign animal
diseases.
As mentioned above, APHIS prohibits the importation of cattle from
countries with known CBPP. Serologic testing of susceptible animals
prior to importation is required. As a further precaution, the United
States requires that every imported animal have an official veterinary
certificate of health from its native country. Imported cattle are inspected
at U.S. ports of entry, where they are further examined, treated, and
quarantined as necessary.
Through cooperation with USDHS, APHIS maintains a constant alert status
to protect American livestock from foreign animal diseases such as CBPP.
What the U.S. Livestock Owner Can Do
Livestock owners can help to protect the U.S. livestock industry by
knowing the signs of CBPP and immediately reporting anything suspicious
to their veterinarian or to an animal disease control official.
Additional Information
For more information contact:
USDA–APHIS
Veterinary Services Emergency Programs
4700 River Road, Unit 41
Riverdale, MD 20737
Phone: (301) 734–8073
Fax: (301) 734–7817
or visit the APHIS Web site at www.aphis.usda.gov.
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