Contents
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