Canine Brucellosis Caused by Brucella Canis

Etiology and Epidemiology Canine brucellosis is caused by Brucella canis (B. canis), a rough, small, gram-negative, intracellular bacterium. Other Brucella species, i.e., B. abortus, B. suis, have occasionally caused canine infections but they are not discussed here. The canine brucella was first recognized in 1966 as a cause of abortions and reproductive failures and it has since been recognized in several countries. It is especially common in Central and South America, in the southern states of the United States, and has been diagnosed in commercial or research breeding kennels (beagle) in several other countries, including Japan and, more recently, in The People's Republic of China. The disease has been reported sporadically in Europe. Humans may be infected; however, dogs and other canine species are believed to be the only true hosts. Natural infections occur most commonly after ingestion of contaminated placental materials or aborted fetuses, vaginal discharges from infected bitches that are in heat or who abort, and during breeding. Following an abortion, organisms may be shed for several weeks or, intermittently, for months following an abortion. Males also may shed organisms in the urine, but bacterial numbers are relatively low, except when urine is contaminated with seminal or prostatic fluids. Prevalence data is meager, but seroprevalence rates appear high (20-30%) in Mexico and Central/South America. Estimates in the southern United States, Japan have been reported to be 7-8% in stray dogs. Food-producing animals are highly resistant. True prevalence rates are unknown and other epidemiological aspects of canine brucellosis are lacking.