Hundreds of buffalo from America's last great remaining wild herd could be sent for slaughter after being driven from Yellowstone national park by high snow and harsh temperatures, conservationists warned today.

Nearly 400 buffalo have been captured and penned on the northern boundaries of the park after wandering in search of food during an unusually severe winter.

Authorities were testing the animals for exposure to brucellosis, a disease that can cause pregnant cattle to abort. Those that test positive will be sent for slaughter under a controversial programme intended to protect Montana's cattle industry.

"It's a nightmare that is going on here," said Jeff Welsch, a spokesman for the Greater Yellowstone Coalition. "One third of the herd was slaughtered under the same scenario in the winter of 2007-2008, and now we are going back to a similar situation."

News reports said today 53 of the 161 buffalo tested so far were positive for brucellosis.

Meanwhile, conservation groups were seeking court injunctions to stop the authorities from shipping the corralled animals to a slaughterhouse on Monday.

Welsch said hundreds more buffalo were lined up at the borders of the park. If park officials do not succeed in driving them back, those animals too were at risk of slaughter.

There are about 3,900 buffalo left in Yellowstone national park, the last genetically pure herd remaining of the millions that once roamed the American West. Their existence has come into conflict with Montana's billion-dollar cattle industry. Montana has a zero-tolerance policy for buffalo that wander out of the park – in part because of pressure from ranchers who fear the animals will infect their cows.

Conservationists argue there is little justification for the government's brucellosis regime. Although the disease is endemic to the Yellowstone herd there has never been a documented case of transmission from wild buffalo to cattle.

They say the prevention programme has taken a terrible toll on the buffalo. In 2008, after another unusually harsh winter drove the animals out of the park in search of food, some 1,600 were captured and killed, including 1,400 carrying brucellosis.