Brucellosis

Original article by Lily Stanley | Last updated on 28/6/2014
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Organism

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
 

Transmission

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

Epidemiology

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.
 

Pathogenesis

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
 

Diagnosis

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

Treatment

Long course of doxycycline + rifampicin/gentamicin
 

Prevention

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