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Gram negative aerobic coccobacillus
3 species responsible for human infection:
  • B. Abortus (disease of cattle) – Africa and india
  • B. melitensis (disease of sheep, goats and camels) – Mediterranean middle east and central & south America.
  • B. Suis (disease of pigs) – still problem in USA
Incubation: 1 week to several months
Brucella bacteria


Organisms ingested or inhaled and taken up into the reticuloendotheial system.
Sources: unpasteurised dairy products, contaminated meat, placentae or infected animals


People that work with animals like Farmers and vets are at risk
Frequency is highest in agricultural societies
Middle east and southern Europe are high risk areas.


Brucella bacteria survive intracellularly by avoiding the immune system in several ways:
  • Poor inducers of inflammatory cytokines (ie TNF/interferon)
  • Don’t activate the complement system
  • Inhibit programmed cell death

Following replication the bacteria are released and cause cell lysis. This can lead to systemic disease and can involve almost every organ system.

Clinical course

Usually self limiting over 2-3 weeks
Rarely fatal unless complicated by endocarditis
Relapse may occur, and symptoms may continue for years


Blood or bone marrow or clean catch urine or CSF cultures
Serology for brucellosis antigen
May also see:
  • Lymphopenia
  • Abnormal LFTs


Long course of doxycycline + rifampicin/gentamicin


Hygiene whilst handling animals
Pasterised milk
Vaccination available for cattle but not humans


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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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