Brucellosis in Dogs

What is canine brucellosis?

Canine brucellosis is a contagious bacterial infection caused by the bacterium, Brucella canis (B. canis). This bacterial infection is highly contagious between dogs. Infected dogs usually develop an infection of the reproductive system, or a sexually transmitted disease. Different species of Brucella infect sheep, goats, cattle, deer, elk, pigs, and other animals.

What are the signs of brucellosis?

Male dogs infected with brucellosis develop epididymitis, an infection in part of the testicle. A dog with a newly acquired infection will often have an enlarged scrotum or an enlarged testicle and may have a skin rash on the scrotum. The dog may be infertile. In chronic or long-standing cases, the testicles will atrophy or become shrunken.

Female dogs infected with brucellosis develop an infection of the uterus. This may cause her to be infertile, have difficulty getting pregnant, or she may abort in the late stages of pregnancy. She often has a persistent vaginal discharge. Typically, a pregnant dog with brucellosis will abort at 45-55 days of gestation or will give birth to stillborn or weak puppies that may die a few days after birth.

During the early stages of brucellosis, enlarged lymph nodes are sometimes seen, although fever is uncommon. Occasionally, B. canis will infect the intervertebral discs, eyes, kidneys, heart or brain. If the bacteria infects these other tissues, the signs will be related to the bodily system that is infected.

How is canine brucellosis spread?

Large numbers of B. canis bacteria are shed in the genital secretions (semen or vaginal discharges) of an infected dog. Smaller amounts of bacteria may also be shed in the dog's urine or saliva. After a female dog aborts a pregnancy because of brucellosis, she will continue to discharge fluids infected with the bacteria for 4-6 weeks after the abortion.

Dogs are exposed to the disease via contact with infected bodily fluids. Although the most common route of infection is oral (i.e., from licking contaminated urine or discharges from the reproductive tract or licking or chewing placental material or aborted fetuses), dogs can also pick up an infection through sexual transmission, inhalation (sniffing contaminated urine or other discharges), or through other mucous membranes such as the eyes.

How is canine brucellosis diagnosed?

The infection is usually diagnosed by a blood test. The most common blood test is called a rapid slide agglutination test or RSAT, and it can detect infections after three to four weeks. This test is used for screening of breeding dogs, and negative tests are reliable unless the dog has been recently exposed to the disease. False-positive tests are relatively common, and any dog that tests positive with the RSAT test should have the disease confirmed with an advanced test.  Likewise, the Tube Agglutination Test (TAT), which provides an actual measurement (titer) of antibodies against B. canis, can also be used as a screening test.  A more specific test, called an agar gel immunodiffusion test (AGID), will identify infected animals between 12 weeks and 1-year post-infection.  Other tests include ELISA assays, PCR testing, and bacterial culture to look for the B. canis organism itself.

What is the treatment for canine brucellosis?

Although antibiotics (most often minocycline or doxycycline, possibly enrofloxacin) can be used to help control the infection, no treatment is completely effective at eliminating the bacteria, as it can persist in tissues.  As a result, any dog that has been infected with B. canis should be considered to be infected for life. Even if the acute infection can be controlled with antibiotics, the dog may shed bacteria intermittently for the rest of its life.

Surgical sterilization of the infected dog will decrease shedding of the organisms into the environment, thereby reducing the risk to other dogs. Supportive treatment for any other organ system that has been affected by the bacteria is also geared to the specific case.

How can brucellosis be controlled?

Any kennels reporting a brucellosis case must be immediately quarantined, and infected animals must be prevented from breeding and, preferably, eliminated from the kennel. The bacteria itself does not survive well in the environment, although people working with infected dogs should wear protective equipment such as gloves.

"Any kennels reporting a brucellosis case must be immediately quarantined..."

Brucellosis has been reported in dogs in both the United States and in Canada, with many of these cases originating in dogs imported from other parts of the world. Since the disease is a major threat to the breeding capability of dogs, all dogs used for breeding purposes should be tested regularly (e.g., every 3-6 months, depending on exposure to other dogs), and new dogs should never be introduced into a kennel situation until they have been quarantined and then tested for the disease. Most experts recommend performing two blood tests four weeks apart, near the end of the quarantine period.

In the United States and in some Canadian provinces,  brucellosis is a reportable disease, meaning that the disease is of great public health importance, and veterinarians and physicians are required to report all positive cases to federal or provincial authorities.

Am I at risk for developing brucellosis from an infected dog? 

Brucellosis is a zoonotic disease, or a disease that can be transmitted from animals to humans. Although people can become infected by coming in contact with infected animals, it is uncommon for a person to get a brucellosis infection from a dog.

Breeders and veterinarians exposed to the blood or other secretions of infected animals are at an increased risk of developing an infection; pet owners are not considered to be at high risk for infection because they are less likely to come in contact with blood, semen, or uterine discharges from an infected dog.

However, people with compromised immune systems should avoid contact with a dog that is diagnosed with brucellosis.

People who come in contact with breeding dogs, newborn puppies, or aborted fetuses should use caution and practice good sanitation. Whenever possible, wear disposable gloves before handling newborn puppies or cleaning an area where a dog has whelped. After removal of the disposable gloves, wash your hands thoroughly with soap and water and rinse well.