Last revised by Dr Ian Bickle on 16 Jul 2022

Brucellosis is a global zoonotic infection secondary to any of the four Brucella spp. that infect humans. It can be focal or systemic but has a particular affinity for the musculoskeletal system. 

Brucellosis occurs worldwide but is particularly prevalent in Mediterranean regions, Middle East, South Asia, and Central and South America 2. Risk in these countries is partly attributed to ineffective public and domestic animal health services.

Patients present typically with fever, which can be undulating and lasts for 2-3 weeks. Arthralgia, myalgia and back pain are also common 5. Brucellosis may affect any system and so signs and symptoms are heterogeneous. Please see neurobrucellosis for manifestations of central nervous system infection. 

Due to the insidious onset of disease, brucellosis presents in both acute and chronic forms. A variety of methods to detect IgM and/or IgG antibodies have been proposed, with some conflict in the literature regarding which is optimal for diagnosis. The Rose Bengal test, serum agglutination test, Coombs test, lateral flow immunochromatography assay, a fluorescence polarization assay, indirect ELISA assays, and the immunocapture BrucellaCapt test may be used independently or in combination to confirm Brucella infection 6.

Brucella spp. are gram-negative coccobacilli, which are mostly spread animal-to-human via unpasteurised dairy products. There are a number of species that act as primary hosts to infect humans as secondary hosts. There are four main species that infect humans 1-4:

  • Brucella melitensis (camel, sheep),
  • Brucella suis (pigs),
  • Brucella abortus (cattle),
  • Brucella canis (dogs).

Rarely, the more recently discovered fifth and sixth species ​B. ceti and B. pinnipediae - found in marine mammals - have been isolated in the context of neurobrucellosis. The CDC has classified the Brucella abortus, canis, and ​suis species as "select agents" due to their potential to be aerosolized for bioterrorism purposes. 

Brucellosis may affect any body part and may be focal or systemic, but it has an affinity for infecting the spine:

Brucella is eponymously named in honor of the early investigatory work into disease pathogenesis performed by Scottish microbiologist Sir David Bruce (1855-1931), who was born in Melbourne, Australia 9

Of note, B. abortus is so named as it causes spontaneous abortion in the third trimester in cattle 7

Historically, brucellosis was also known as undulant fever, but this is rarely used contemporaneously.

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Cases and figures

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