Bison Populations Can Be Restored After Removal From Infected Herds
February 28, 2014

Bison Populations Can Be Restored After Removal From Infected Herds

Brett Smith for - Your Universe Online

About half of the Bison in Yellowstone National Park test positive for exposure to brucellosis, a bacterium that causes pregnant animals to prematurely abort their young.

According to the results of a new study published in the Journal of the American Veterinary Medical Association, non-infected bison can be safely removed from an infected herd and used to start new herds.

The study represents a promising future for an animal that has been driven from the American plains and toward extinction.

"The results of this study indicate that under the right conditions, there is an opportunity to produce live brucellosis-free bison from even a herd with a large number of infected animals like the one in Yellowstone National Park," said Jack Rhyan, a veterinary officer at the USDA Animal and Plant Health Inspection Services (APHIS). "Additionally, this study was a great example of the benefits to be gained from several agencies pooling resources and expertise to research the critical issue of brucellosis in wildlife."

From 2005 to 2008, more than 200 bison calves born in Yellowstone were moved just outside the park to a quarantine facility at Corwin Springs, Montana. For the study, blood samples were gathered from the animals every 30 to 45 days and tested for brucellosis. Bison that tested positive were euthanized and the survivors were tested until they had two consecutive negative tests. Since the main mode of brucellosis transmission is through abortion and birthing events, all the animals were held until their first calf – along with any birth fluids, or blood – showed no evidence of the disease.

These brucellosis-free animals continued to be healthy over the course of the seven-year study. Evidence of brucellosis was not found in either subsequent newborn calves or their mothers.

"This will help defuse the argument about brucellosis, that the animals are carrying brucellosis and will give it to cattle around them," Rhyan told the Associated Press. "I'll feel more positive after 1,000 animals have gone through. That's just caution because this disease sometimes crops up where you never think it can."

A movement to restore bison to large swaths of land is gaining momentum across the United States and Canada, and brucellosis-free bison may soon be required to seed those landscapes. The genetics of Yellowstone bison are particularly important because they are considered to be free of cattle genes and represent bison that existed on the Great Plains for millennia.

"This study represents an important milestone in bison conservation and these research findings enable us to practice genetic rescue from brucellosis infected bison herds,” said Keith Aune, a bison project coordinator at the Wildlife Conservation Society. “The Yellowstone animals passing through this system of testing are critical to conserving the diversity of the bison genome over the long term. We've also learned a great deal about brucellosis blood testing and how to better interpret results when screening animals for this disease. It is our hope that several satellite herds of Yellowstone bison can be assembled from the animals that graduate through this quarantine process."