is a bacterial disease that affects livestock and wildlife,
sometimes causing cattle to abort their first calf post-infection.
While abortions have been documented in wild buffalo, such
incidents are rare, and the impact of the disease on Yellowstone
buffalo and elk is insignificant. Brucellosis, which originated
in European livestock, was first detected in Yellowstone's
buffalo in 1917 after some buffalo were fed milk from infected
FACT: There has never been a documented case of a wild, free-roaming
buffalo infecting domestic cattle with brucellosis.
- While some of Yellowstone’s buffalo test positive
for antibodies to brucellosis, a positive test indicates only
that the animal has been exposed to the disease, which in
many cases simply means that the animal has acquired disease
resistance. Buffalo who test “positive” are not
necessarily infected with the disease or capable of transmitting
it to other buffalo or to cattle.
- The already negligible risk of disease transmission is further
reduced because (1) virtually all cattle near Yellowstone
are already vaccinated against brucellosis, (2) cattle and
buffalo generally do not occupy the same area at the same
time (buffalo in the winter, cattle in the summer) (See FAQ-
But there are no cattle in West Yellowstone, right?), and
(3) transmission occurs via fluids and tissues associated
with either a live birth or an aborted fetus; bull buffalo,
calves, and female buffalo that are not pregnant thus would
not pose a disease threat, even if they were to come into
contact with domestic cattle.
Capture, Test, and Slaughter. All buffalo
that test positive are sent to slaughter, including bulls,
even though transmission is thought to occur primarily (or
only) when an infected female gives birth or aborts. In spring
of 2002, when the Yellowstone buffalo population exceeded
an arbitrary population “cap” of 3,000, MDOL sent
more than 100 buffalo to slaughter without even testing them
first. In 2003, the National Park Service—the agency
responsible for protecting the buffalo and other Park wildlife—sent
more than 200 buffalo to slaughter before any disease testing
was conducted on these individuals.