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Brucella Canis Bacteria
Members of the genus Brucella exist as intracellular pathogens in mammals. They do not exist as commensal species (those which derive a benefit from a host) nor are they found free-living in the environment. Although they can be recovered temporarily from environmental samples associated with infected animals, this is not important since direct or close contact is required for transmission.
The Brucella genus is usually divided into virulent (B. abortus, B. melitensis) and low pathogenic (B. canis, B. ovis). For the virulent strains, transmission primarily occurs through fluids or tissues associated with the birth or abortion of infected fetuses or offspring through milk.
Venereal transmission is an important route of infection for B. canis, B. ovis, and B. suis. B. canis can also be shed in urine, milk, nasal secretions, and saliva, and has also been recovered from feces.1
The organism is engulfed by macrophages and initially transported to lymph nodes. The organism replicates within lymphocytes for an indefinite period of time. Antibody titers rise after initial infection and fall as the number of bacteria in the bloodstream decreases. Decreasing serum antibody titers do not indicate clearing of infection from the body.2 With the development of an effective body response, the bacterial proliferation is controlled and the bacteria are gradually eliminated. Nevertheless, the bacteria may persist in their host cells for months or even years and recommence replication if the activity of the immunologic control mechanism declines.3
The organs most commonly affected in male dogs are testicles and epidydimes (portions of the seminal tubes immediately attached to the testicles), causing inflammation, dermatitis, and infertility. The organism can be recovered from the testicles within 5 weeks of infection. Brucella canis has also been reported as a cause of uveitis, meningitis, diskospondylitis, glomerulonephritis, osteomyelitis, pyogranulomatous dermatitis, and cystitis in the dog.
References
1. Pathogenesis of Bacterial Infections in Animals edited. Glenn Songer, Carlton L. Gyles, John F. Prescott, Charles O. Thoen
2. Canine and feline theriogenology. Shirley Dianne Johnston, Shirley D. Johnston, Margaret V. Root Kustritz, Patricia Schultz Olson
3. National Institute of Allergy and Infectious Diseases, NIH: Volume 2. Vassil St. Georgiev, Anthony S. Fauci, M.D. (2009)
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