Brucellosis is a generalized infection of worldwide occurrence. It is highly contagious, affects many animals and can be transmitted to man. Infection often begins without clinical signs. It affects many other different organs in animals and signs of the disease are influenced by the nature and extent of the infection and the species involved. These may be abscesses (horses, cattle and reindeer), lameness and swelling of joints, chronic infections of the bones and joints in livestock and reindeer. In ruminants, brucellosis commonly induces abortions in the latter half of gestation and may result in infertility. Important economic losses arise from aborted calves, lambs, etc. and through subsequent slaughter of livestock affected by the disease.
Brucellosis is reported throughout the world. It affects mainly goats, cattle and swine, but is also found in sheep, horses, dogs, camels and other domestic animals, and in a large variety of wild animals, notably bison, elk, caribou and reindeer. Other groups of animals have been found to have had brucellosis but not to epidemic proportions. These include domestic poultry and wild birds, hares and rabbits, and other wildlife such as the American desert wood rat. These groups play a role as carriers of the disease, and, as in the case of hares in Denmark (where the disease had been eradicated) provide a threat of reinfection.
The infection can be caught by humans drinking unpasteurised milk or by being in contact with infected animals and is one of the diseases being explored because of its value in biological warfare.