Infectious Agent

Facultative, intracellular, gram-negative coccobacilli; known human pathogens include Brucella abortus, B. melitensis, B. suis , and B. canis .


Most commonly through consumption of unpasteurized dairy products or undercooked meat from infected animals and direct contact with infected animals, especially those that have recently given birth. Since wildlife can be reservoirs for Brucella spp., hunting can be a risk for exposure as well. Brucella can enter the body via skin wounds, mucous membranes, or inhalation. Person-to-person transmission is rare.


High-risk regions include the Mediterranean Basin, South and Central America, Eastern Europe, Asia, Africa, and the Middle East. In these areas, brucellosis is primarily enzootic in cattle, sheep, and goat populations, as well as feral swine.

Clinical Presentation

Incubation period is usually 2–4 weeks (range, 5 days to 5 months). Initial presentation is nonspecific, including fever, muscle aches, fatigue, headache, and night sweats. Focal infections are common and can affect most organs in the body.


Blood culture is the diagnostic gold standard, but is not always positive. If culture of blood, bone marrow, or other clinical specimen is performed, the laboratory must be informed that Brucella is suspected, as the culture takes longer to grow and laboratory personnel require additional personnel protective equipment when handling cultures. A serum agglutination test is the most common serologic approach, but other serology assays (including ELISA) and PCR have been used to make a diagnosis. Brucellosis is a nationally notifiable disease.


Doxycycline, rifampin, trimethoprim-sulfamethoxazole, fluoroquinolones, aminoglycosides, and other agents have been used in various combinations for a minimum of 6–8 weeks. If bacteria localize in organs and tissues and cause focal infection, surgical drainage could be indicated. Late diagnosis or inappropriate therapy can result in chronic disease or relapse.


Avoid unpasteurized dairy products and undercooked meat. Wear protective equipment when dressing or butchering wild animals potentially infected with Brucella spp. In clinical microbiology laboratories, if Brucella spp. is suspected, culture isolates should be handled under BSL-3 conditions.

CDC website:


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Maria E. Negron, Rebekah Tiller, Grishma A. Kharod