Brucellosis

Brucellosis is one of the most frequently encountered zoonotic diseases, with approximately 500,000 cases identified annually worldwide. Brucella are small, gram-negative, nonmotile, non–spore-forming, aerobic coccobacilli that can reproduce intracellularly only. Historically, human disease was thought to be caused by several different species, including Brucella melitensis, Brucella abortus, Brucella suis, and Brucella canis. However, these are now thought to be closely related organisms in a single species. The bacteria can survive for many days to weeks in dairy products but are killed by boiling, pasteurization, and souring or lactic acid fermentation of milk.

Brucellosis was first described in 1859 by British Royal Army Medical Corps (BRAMC) physician J.A. Marston among troops in Malta during the Crimean war. In 1886, David Bruce, another BRAMC physician, isolated the bacteria, later named for him, from the spleen of an affected patient in Malta. Approximately 10 years later, a Danish veterinarian, Bernhard Bang, isolated Brucella species (B abortus) from cattle with contagious abortions.

Disease is most commonly acquired from contaminated, unpasteurized sheep, cow, goat, and camel milk, and less frequently from direct contact with infected animals among farmers, veterinarians, and abattoir workers. Brucellosis is found worldwide but especially in developing countries, with the highest incidence in the Mediterranean basin, Arabian Peninsula, Indian subcontinent, Mexico, and South and Central America. The illness has also reemerged in Eastern Europe since the collapse of the Soviet Union. Historically, human brucellosis was found in the United States, but rates have declined with the eradication of bovine brucellosis by cattle immunization programs and test-and-slaughter techniques. Currently, in the United States there are fewer than 0.5 cases per 100,000 people, …