HELENA, Mont. — A heifer has tested positive for the disease brucellosis on a Montana ranch near Yellowstone National Park.

State veterinarian Marty Zaluski said Thursday the cow was identified during voluntary testing on a ranch within the state’s brucellosis Designated Surveillance Area. The Madison County ranch has been placed under quarantine while the source of the infection is investigated.

Ranches within the Designated Surveillance Area are subject to increased testing for brucellosis, a bacteria that infects bison and elk. It can cause animals to abort their young.

This is the ninth brucellosis affected herd since the creation of the DSA in 2010.

Officials have said elk are the likely source of brucellosis infections in cattle in Montana, Wyoming and Idaho.