Delaware County Cooperative Extension

Bovine Tuberculosis

Bovine Tuberculosis
Barry Whitworth, DVM, Area Food/Animal Quality and Health Specialist for Eastern OK

In 1917, Congress appropriated the money to begin the State-Federal Cooperative Bovine Tuberculosis
Eradication Program. The program was started to reduce the number of human tuberculosis
cases that were the result of being infected with bovine tuberculosis (bTB). Most human cases
were caused by humans consuming unpasteurized dairy products. Although the number of cases
of tuberculosis in cattle have been greatly reduced over the past 100 years, the disease has not
been eradicated from the United States. New cases continue to be found in cattle and on occasion
in other animals. White-tailed deer have been a problem in the state of Michigan. Just in the
past few months, Indiana found positive cases in cattle and deer. South Dakota is the latest state
to find cattle with the disease. New Mexico and Texas are also dealing with herds infected with
tuberculosis. These few infections indicate a need for producers to remain vigilant in keeping tuberculosis
out of their herds.
Bovine tuberculosis is caused by Mycobacterium bovis. This bacteria is contagious to other animals
and humans. The bacteria survives in moist warm environments for long periods of time.
The organism can be found in exhaled air, saliva, feces, and milk. Rarely, the bacteria is found in
semen, urine, vaginal, and uterine discharges from infected cattle. The organism is found more
often in dairy breeds than beef breeds. This is due to dairy cattle being kept in close confinement.
Most cattle get the bacteria from other infected cattle. In rare circumstances, people infected with
the bacteria may infect cattle. In the northern portion of the Lower Peninsula in Michigan, the bacteria
is well established in the white-tailed deer population. These deer have infected cattle. Most
cattle will inhale the bacteria or ingest it. Calves are easily
infected from ingesting colostrum and milk from an
infected cow.
Tuberculosis in cattle usually progresses over a long period
of time, however, it can be fast and progress quickly.
Clinical signs of cattle infected with M. bovis depend on
the location and severity of the infection. Early in the
disease, cattle display very few or no signs of sickness.
Common clinical signs seen in cattle are emaciation,
weakness, anorexia, and fluctuating fever. The lymph
nodes will enlarge. In the final stages of the respiratory
form of the disease, cattle will have bronchopneumonia
which results in a moist cough, labored breathing, and
an increased heart rate. If the digestive system is infected,
the cattle may have diarrhea or be constipated.
In the end, most cattle will be extremely thin and have
severe respiratory problems.

Diagnosing tuberculosis in cattle based on clinical signs can be difficult. Most cattle are found at
routine inspections at slaughter facilities. They are also found when conducting surveillance tests in
infected areas and when state regulations require testing the animals before entering the state.
When a veterinarian test for the disease in cattle, they will do a tuberculin test. The veterinarian will
inject the tuberculin intradermally. Any swelling at the injection site indicates a positive reaction.
Since tuberculosis is a reportable disease, any positive test would be reported to the state and/or
federal veterinarians. The state and/or federal veterinarians would confirm the test with additional
tests. In most positive cases, the cattle are sent to slaughter. In some rare cases, the state and
federal authorities may allow the cattle to remain quarantined to the premises.
Since treatment of the disease is difficult and expensive, and no vaccine is available, prevention is
the key to controlling the disease. Preventing the introduction of tuberculosis into the cattle herd
begins with biosecurity. The ideal situation is to maintain a closed herd. If this is not possible,
ranchers should purchase replacement bulls, cows, and heifers from a reputable seed stock source.
When purchasing cattle from states with bovine tuberculosis, producers should consider TB testing
the cattle prior to entering their ranch.
White-tailed deer in Oklahoma have never been found to have bovine tuberculosis. Even knowing
that fact, cattle should not be allowed to have contact with white-tailed deer. One way to prevent
this contact is prohibit the feeding of deer on their ranch. Researchers at Michigan State University
have proven that the organism will survive
on salt blocks, so producers may need to
cover mineral and/or salt feeders at night.
Bovine tuberculosis occurs rarely in cattle
but producers should be aware the problem
does exist. They should do everything
possible to keep the disease out of
their herds. If a producer would like more
information on the disease, they should
contact their local extension educator or
their local veterinarian.