Brucellosis is an infection caused by bacteria of the genus Brucella. The most common species of Brucella in companion animals is Brucella canis, which typically causes infection in dogs. This bacterium is very rare in Ontario - in a survey of 2000 dogs, only 0.3% had evidence of exposure to B. canis. So it was unusual that a case of canine brucellosis was recently diagnosed in the province, until it was discovered that the dog originally came from a rescue shelter in the southern USA - an area where exposure to the bacterium is much more common (approximately 8% of dogs).
Brucellosis in dogs typically causes reproductive problems such as infertility and an enlarged scrotum in males, and late-term miscarriage in bitches (breeding females), with few or no other signs of clinical illness. But in some cases the bacteria have been found to infect tissues other than the reproductive tract, including intervertebral discs (leading to back problems), the eyes, the kidneys, or the tissues around the brain and spinal cord (i.e. the meninges). The bacteria, and antibodies to the bacteria, can be very difficult to detect in the early stages of infection. The infection is usually diagnosed by a blood test, but it may take 8-12 weeks before test will yield a positive result. There are also problems with high numbers of false-positive test results due to cross-reaction with other species of Brucella. Any positive test result should therefore be confirmed by a second, different laboratory test.
Human infection with any species of Brucella is now uncommon. When illness does occur, the signs are often non-specific (e.g. fever, headache, myalgia), but more severe infections have been reported. Transmission of B. canis from an infected dog to a person is possible. The bacterium is transmitted by contact of a mucous membrane (e.g. eyes, nose, mouth) with blood, urine, milk, semen, or vaginal discharge from an infected animal. The highest-risk materials (i.e. most likely to contain a high number of the bacteria) are placental tissues and fluids that are passed during whelping (delivering puppies). Treatment for infection is available, but the course is often long and recurrence of infection can occur.
Although brucellosis is very rare in dogs in Ontario (and Canada in general), here are a few things you can do to help avoid B. canis:
- Always wash your hands right away if you accidentally come in contact with blood, urine, milk, semen or vaginal discharge from any dog.
- Prevent contact between your dog and urine, milk, semen or vaginal discharge from other dogs, especially if you travel with your dog to an area where the prevalence of B. canis is relatively high (such as the southern USA).
- Dogs used for breeding should be tested for B. canis. Many breeders will require dogs to be tested before allowing their animal(s) to be used, because the infection can be transmitted through breeding and can have such detrimental effects on fertility.
- Newborn pups should be handled as little as possible, but if you must handling them wear disposable gloves and wash your hands as soon as you take your gloves off. Exercise the same precautions when cleaning up the area where a bitch has whelped.
More information about brucellosis can be found on the CDC's Brucellosis website.