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Humans and Brucella Species

Exposure to most species of Brucella, such as those associated with certain types of animals, could potentially lead to infection.

When infections in humans occur, the following Brucella species are more often responsible:

Brucella melitensis*

  • Principal hosts - goats and sheep
  • Most pathogenic in humans
  • Considered to be eradicated in the U.S. since the early 1970s.
  • Sporadic cases in humans in the U.S. occur related to consumption of unpasteurized dairy products from countries where the disease is present.

Brucella abortus*

  • Principal host - cattle
  • Eradication of B. abortus from cattle is nearly complete in the U.S., but the disease still occurs in some wild bison and elk herds in the western U.S.

Brucella ovis and neotomae

  • Not known to be pathogenic for humans

Brucella suis*

  • Principal host - swine
  • Since B. suis is normally found in pigs, wild hog (feral swine) hunters are at risk of becoming infected when they field dress infected pigs.

Brucella canis

  • Principal host - dog
  • Individuals who are in close contact with dogs, or breeders/veterinary staff who assist with birthing are at risk of becoming infected.
  • CDC does not currently perform serological testing for Brucella canis

Brucella ceti and pinnipediae

  • Recently discovered in marine mammal species
  • Few human cases diagnosed with neurobrucellosis

*Three types of the bacteria that cause brucellosis – Brucella abortus, Brucella melitensis and Brucella suis – are designated as select agents. This means that they have the potential to be developed as bioterrorism agents due to their ability to undergo aerosolization.

For more on select agents, visit www.selectagents.gov.

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