BILLINGS, Mont. (AP) -- Montana livestock officials say a bull from a Madison County cattle ranch has tested positive for the disease brucellosis.

Wednesday's announcement marks the state's third brucellosis infection in a cattle herd since last November and the fifth since 2007.

Officials say the infected animal was removed from the herd and slaughtered for testing. The ranch was placed under quarantine.

State Veterinarian Marty Zaluski says the infection is not expected to change Montana's brucellosis-free status with the Department of Agriculture. That's because the state has established a special management zone for the disease around Yellowstone National Park.

Eradicated elsewhere in the U.S., brucellosis persists in Yellowstone's wildlife. It can cause pregnant animals to miscarry.

Other animals on the Madison County ranch tested negative for the disease. More tests are planned.

Copyright 2011 The AP.

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