States worried about brucellosis are imposing strict rules on the import of Montana cattle.

Nebraska state veterinarian Dennis Hughes said cattle coming to Nebraska from Montana's Madison, Gallatin, Park, Sweet Grass, Stillwater and Carbon counties will have to be certified brucellosis-free. All animals older than 18 months will have to test negative for the disease, even if they're not going to market.

State veterinarians from Montana, Idaho and Wyoming have said cattle will continue to be plagued by brucellosis as long as it remains prevalent in wildlife in and around Yellowstone. Brucellosis can cause pregnant cows to abort their calves.

Idaho, Washington, Colorado, North Dakota and South Dakota also drafted rules for importing Montana cattle, but they are less stringent than Nebraska's.