Scientists hope to prevent the disease from spreading to nearby livestock by vaccinating the wild bison. No cattle herds in the U.S. are currently known to be infected, although some near Yellowstone have been sickened in the last decade.
An incurable disease, brucellosis can cause abortions in cattle, bison, elk, and feral swine. It can be transmitted to humans through contact with infected animals or consumption of unpasteurized dairy products. In humans, it's called undulant fever, and causes severe flu-like symptoms.
Wildlife reservoirs of brucellosis in the U.S. include bison and elk (which carry Brucella abortus) and feral swine (which carry B. suis). The animals often come in contact with cattle, especially in winter when bison, elk, domestic livestock and swine are all foraging for the same food. B. suis can be transferred to farm animals or people.
Leading the team on the bison vaccination study is Steven Olsen, a veterinary medical officer at N.A.D.C. Researchers monitored animals to determine the natural course of B. abortus in female bison and their offspring. They found the disease in bison mimics the characteristics seen in cattle.
Although brucellosis has been nearly eradicated in the U.S., mostly through cooperative federal and state programs dating back to the 1950s, its continuing spread through wildlife in the Yellowstone area has raised concern among cattle producers. There is currently no eradication program for B. suis, Mr. Olsen said.
The difficulty in differentiating between B. abortus and B. suis is among the concerns of Mr. Olsen and his colleagues, microbiologists Fred Tatum and Betsy Bricker, because a national brucellosis eradication program only targets B. abortus.
The National Park Service is also conducting an environmental impact study on a proposal to spend $9 million for a new brucellosis eradication program in Yellowstone over the next 30 years.
Study results have been published in Vaccine magazine.