Montana Department of Livestock

Here to serve the people of Montana and its livestock industry.

Animal Health Bureau

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Department of Livestock
Animal Health Bureau
PO Box 202001
Helena, MT 59620-2001
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Brucella canis in Montana



B. canis is a zoonotic reportable disease in Montana per Administrative Rule 32.3.104. While the department has quarantine authority, cases involving single animals or cases isolated to a private residence are not routinely quarantined, provided animals are also spayed/neutered and the owner agrees to management practices that would prevent the spread of disease to other animals or to people.



Clinical signs in intact animals include abortion, infertility, and orchitis.  However, recent cases have involved spayed/neutered dogs who may present with more general signs such as lethargy, lymph node enlargement and lameness/back pain due to discospondylitis. Unfortunately, the infection may go unnoticed for years, especially in animals infected at birth. This bacterium is mainly transmitted by nose/mouth contact with vaginal discharge or birthing fluids from an infected female. Semen, urine, feces, and nasal secretions can also be risks for transmission to people and other animals. Puppies can become infected from their mother during pregnancy as well. For more information on B. canis please click here.



The Department of Livestock has seen an increase in the number of reported B. canis cases, with several cases epidemiologically related based upon where animals originated. Areas with large populations of sexually intact animals, including reservations, may be at a higher risk for B. canis infection.  As a result, animal shelters/rescue organizations and individuals living in or around these areas are at a higher risk for homing infected animals.



The DOL would like veterinarians and animal owners who may work with and live with animals from high risk populations to be aware of the potential disease risk. Through education and surveillance testing, our goal is to reduce the number of positive animals placed into homes, thereby reducing the risk to human health. We encourage animal shelters, animal rescue organizations and concerned animal owners to work with a local veterinarian when trying to evaluate risk for B. canis.

The DOL considers high-risk animals to be:

  • an animal that originates from a population with a high number of intact, stray dogs and/or
  • a mature, intact animal.

High-risk dogs and dogs presenting with clinical signs should be screened for B. canis. Because B. canis, like other Brucella species is difficult to diagnose, The Department has developed a flow chart to help guide screening programs and minimize the risk of false-positive diagnoses.

The flow chart can be accessed here.



The primary management recommendation for positive cases is euthanasia. Sterilization (if intact), antibiotic treatment, and routine testing are offered as a second management option though treating B. canis cases is challenging and should not be considered curative. The bacterium can sequester in areas, such as the prostate, making it difficult for antibiotics to penetrate and eliminate all the organism. Recrudescence may be observed when administration of antibiotics is discontinued resulting in long-term treatment with combinations of medically important antibiotics. Ultimately, many cases result in euthanasia of the animal due to the secondary clinical signs that cannot be effectively treated.



The zoonotic risk of B. canis must also be addressed. While human infections are not common, people who have a compromised immune systems, young children, pregnant women, or persons with artificial heart valves are at risk of severe disease if they acquire the infection. Refer to the MT Department of Public Health and Human Services (DPHHS) document Canine Brucellosis-Q and A for Dog Owners for more information. Please contact your local public health office or physician with questions about the zoonotic risk.


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