What is brucellosis?

board of animal health

Reportable Disease of the Month


What is it?

Brucellosis is a contagious zoonotic disease (affects animals and people) caused by a group of bacteria known scientifically as the genus Brucella. The disease in ruminants is also known as contagious abortion or Bang’s disease.

Brucella abortus primarily affects cattle, bison, deer and elk. Sheep, goats, horses and dogs are also susceptible. Brucella suis affects mainly swine. Brucella ovis and Brucella melitensis affect sheep and goats. Brucella canis affects dogs.

Brucellosis infections in cattle and swine pose a serious threat that could result in significant consequences for domestic and international movement of livestock.  The United States Department of Agriculture Animal Plant and Health Inspection Services administers a cooperative state-federal brucellosis eradication program for these species. Due to the disease eradication efforts implemented under this program, and support and participation of livestock producers, Minnesota along with 49 other states, Puerto Rico and the U.S. Virgin Islands is classified as cattle and swine brucellosis free.

Minnesota administers brucellosis free certification programs for sheep and goats. Disease control efforts also include brucellosis testing for adult, intact dogs distributed by licensed commercial breeders, and a canine brucellosis policy that requires isolation of any dog confirmed to be infected.

How is it transmitted?

Brucella concentrates in the placenta, fetus and fetal fluids, as well as discharge from the vagina. These infected tissues serve to transmit the disease to other animals that may have direct contact with or ingest them. Transmission through broken skin is also possible. The bacteria can be spread by people, equipment and through shared feed and water.

Bacteria can be shed in milk, semen, urine or other reproductive tract discharges, saliva, and nasal and eye secretions for several weeks or months following infection. Intermittent shedding can occur for years. The bacteria has also been known to survive for years in the environment in conditions of high humidity, freezing temperatures and/or limited sunlight.

What are the clinical signs?

Many infected animals do not show outward signs of disease. When present, signs vary by species and individual animal. Signs may include reproductive disease including abortions, stillbirths, decreased milk production, birth of weak offspring, inflammation of the male reproductive organs, and sperm abnormalities. Animals may also present with weight loss, swollen joints and tendons, diseases of the eye, and inflammation of the spinal column.

How is it diagnosed?

Multiple serologic tests are available that test for antibodies produced by the animal’s immune system in response to an infection. Because of the potential for false results, positive tests are confirmed with additional testing to identify the bacteria.

How is it treated?

No treatment is certain to eliminate Brucella infections. Infected cattle and pigs are a dangerous source of infection and are depopulated as part of the United States Department of Agriculture’s Brucellosis Eradication program. Infected dogs are permanently isolated from other dogs not known to be affected or euthanized.

Is there a risk to people?

Yes, humans can become infected by improperly handling infected animals or their afterbirth, ingesting organisms, or by contamination of mucous membranes and abraded skin. Bacteria can survive in raw milk, but this serves as an unlikely source of infection due to routine milk testing and pasteurization.

How can it be prevented?

Infection can be controlled with rigorous implementation of sanitation and infection control measures coupled with testing and subsequent isolation or euthanasia of infected animals. Special care and cleaning should be focused in animal birthing areas. Commercial vaccines are available for cattle, sheep and goats.

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