Canada has closed its border to Montana cattle, horses and other livestock for six weeks or more in response to an outbreak of infectious vesicular stomatitis in 16 Yellowstone County horses.

The disease also has prompted organizers to postpone two Billings Livestock Horse Sales, planned for later this month and in September, and to cancel Malta's 2005 Mustang Stampede rodeo scheduled for next month.

The first case of the disease known as VS was reported Aug. 10 in the Laurel area.

Dr. Tom Linfield, state veterinarian with the Department of Livestock, said Friday that so far, 16 animals have tested positive at 11 locations. All the locations are in Yellowstone County, though other horses are being tested in nearby Carbon, Stillwater and Park counties.

VS is a close relative of hoof-and-mouth disease. The symptoms of the two are identical: excessive drooling and severe lesions on noses, in mouths and around the hooves.