Yellowstone National Park in the U.S is home to about 5,000 bison. The iconic animal has lived in this area since prehistoric times, and was named the U.S. national mammal in 2016. 

Wild animals often suffer from diseases that have no cures or effective vaccines. Brucellosis is a contagious disease that affects 60% of Yellowstone bison. It impacts the reproductive system, causing abortions, weak calves, and reduced milk production. It primarily infects hoofed animals like cattle, bison, and elk; infections in humans are rare. Curiously, it was likely introduced to North America when infected cows were imported from Europe in the early 1860s. 

Since the early 20th century, billions of dollars have funded the management of brucellosis in the United States. The first vaccine was developed in 1982, which has helped to eliminate the disease in farmed cows globally. The economies of the states bordering Yellowstone depend heavily on the farmed animal industry, so the Interagency Bison Management Plan was formed to eliminate brucellosis in Yellowstone, in order to prevent the transmission to animals used for food. In 2000, population control methods were introduced as a yearly slaughter of wild bison that tested positive for the disease.

This 2022 report recommends certain reforms to manage brucellosis in Yellowstone: a successful program for developing vaccines, careful use of contraception, and ongoing efforts to overcome political obstacles. 

Farmers today must vaccinate farmed cows and bison in areas surrounding Yellowstone. However, elk — not bison — are the main spreaders of the disease. Vaccinating the park’s 125,000 elk should, thus, be the priority. Still, bison should also be vaccinated to protect them from the disease and prevent them spreading it back to elk.

Unfortunately, the current vaccines do not prevent infection in elk. They’re injected manually and also require booster doses, which involves capturing the animal repeatedly. New vaccine technologies like oral baits are given “remotely” and by mouth. This advancement is safer, more effective, and cheaper — however, use is not yet widespread. 

Vaccine research is slow to develop because the bacteria that causes brucellosis has been labeled as a bioweapon. Substances on the federal Select Agents and Toxins list are strongly regulated, which becomes challenging for researchers to comply with. The authors suggest that Brucella should be removed from this list as it’s less harmful and easier to treat than many newer bugs.

In addition to effective vaccines, safe population control methods can help manage brucellosis in Yellowstone. Contraception (e.g., sterilization) is practical in this case because preventing pregnancies would reduce the frequency of abortions in animals infected with brucellosis. Since abortions are one of the ways that brucellosis spreads, contraception would check the population growth and slow the spread of disease.

This report is especially useful for advocates of wild animals, and specifically those advocating for bison in the Northwestern United States. Reforming the management of brucellosis in Yellowstone could serve as a model for managing diseases in wild animals in other parts of the world.