No U.S. cattle herds are known to be infected with brucellosis, and all states are listed as class-free for the disease, the Department of Agriculture announced in July.
Lyndsay M. Cole, a spokeswoman for the USDA Animal and Plant Health Inspection Service, said that once again eliminating all known cases of brucellosis among cattle in the United States was a great step, but officials in her agency know work remains because bison and elk in Yellowstone National Park continue to be wildlife reservoirs of the causative organism.
"As long as there's that interaction between brucellosis-positive wildlife and livestock, there's always the possibility of disease," Cole said.
The entire United States was listed as class-free for brucellosis from February to May 2008, the first time in which all states were considered free of the disease since the cooperative state and federal brucellosis program began in 1934. Montana's brucellosis status was downgraded to class A following two reports of infected herds in 2007 and 2008, but USDA-APHIS announced in July the agency was restoring Montana's class-free status.
Both of the infected herds were in the Yellowstone area, USDA information states. State classifications are downgraded from class-free when at least two herds are found to be infected within two years.
Cattle movement restrictions increase as the state's classification decreases.
An annual nationwide brucellosis status report for 2008 states the loss of Montana's Class Free status showed the importance of vigilance against the disease.
"The presence of brucellosis in wildlife populations, such as the free-ranging bison and elk in Yellowstone National Park and Grand Teton National Park, remains a challenge, threatening the brucellosis status of surrounding states," the report states.
Cole said APHIS officials met with state authorities from Idaho, Montana, and Wyoming in June, and state and federal government entities have been developing a brucellosis management plan for the ranches that surround Yellowstone.
The AVMA backgrounder on brucellosis is available at www.avma.org. Click the "Reference" bar, then on "Animal health."
The AVMA brucellosis policy is also available through the reference section here.