Disease Source Checked, Herd Quarantined

REDFIELD, Iowa (DTN) -- A beef bull in the southwest part of Montana in Beaverhead County has tested positive for brucellosis.

Brucellosis is a reproductive disease more commonly found in wild bison and elk, especially in the Greater Yellowstone Area, and will often be transmitted to cattle. While all states have brucellosis-free status, surveillance efforts are ongoing in high-risk areas. This bull, from a herd within Montana's Designated Surveillance Area (DSA), was taken to a livestock market in late July and suspicions were it had brucellosis. The animal was euthanized and taken for necropsy at the Montana Veterinary Diagnostic Laboratory, according to a news release by the Montana Department of Livestock (MDOL).

"This detection shows our program works. Early testing prevents infected cattle from being shipped," said MDOL Veterinarian Brenee Peterson. "While detections of brucellosis are a hardship on operations, this detection is still a reflection of the success of our state brucellosis program."

The disease was confirmed on Aug. 15 by the United States Department of Agriculture's National Veterinary Services Laboratory in Ames, Iowa. The herd that the bull originated from has been placed under quarantine for further epidemiological investigation.

Brucellosis, caused by the bacteria Brucella abortus, will primarily affect cattle by causing abortions, stillbirths, and weak calves and can also lead to reduced milk production and infertility. Symptoms include weight loss and swollen joints, but some infected cattle may not show signs of illness.

The surveillance program is set up to catch animals before they are shipped or mixed with other livestock herds. MDOL traces the affected animal back to the originating herd and tests other animals it may have been in contact with.

This is the 14th herd affected by brucellosis in the surveillance area of Montana since 2010, with the most recent in April 2023. The source of the current infection hasn't been determined, but previous infections traced to wild elk.

"Through the work of DSA producers and local veterinarians, we continue to detect the disease early and prevent the export of a brucellosis infected animal to one of our trading partners," said Peterson.

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

Follow her on social platform X @JennCattleGal

(c) Copyright 2025 DTN, LLC. All rights reserved.