BISMARCK, N.D. (AP) -- North Dakota's state veterinarian is cautioning ranchers to make sure their livestock is vaccinated against anthrax.

Dr. Susan Keller says a case has been confirmed in a beef cow in Stark County. It's the first confirmed case in the state this year.

Anthrax bacteria spores lie dormant in the ground and become active under extreme weather conditions such as flooding or drought. North Dakota usually has a few anthrax cases every year. An outbreak in 2005 killed more than 500 cows and other animals.

Keller says an effective anthrax vaccine is readily available through licensed veterinarians.

Copyright 2012 The AP.