CAUSES
β’ Brucella ingestion from tissue or milk
β’ Worst disease: B. melitensis, B. suis ; also B. canis, B. abortus . Enter through mucous membrane, broken skin, occasionally inhaled. Facultative intracellular parasite, releases endotoxin when destroyed.
β’ Person-to-person transmission rare; sexual, vertical, possibly breast milk.
--------------------------------------------------------------------------
DIFFERENTIAL DIAGNOSIS:
β’ Many non-specific systemic febrile illnesses; a great mimic
β’ Tularemia
β’ Psittacosis
β’ Rickettsial disease
β’ Tuberculosis
β’ Visceral leishmaniasis
β’ Other disease of infected organs
β’ HIV infection
OTHER TESTS :
* SERUM BRUCELLA AGGLUTININ LEVELS - HIGH
* SERUM ANTIBODIES CAN BE DETECTED BY - STANDARD TUBE AGGLUTINATION TEST, 2-MERCAPTOETHANOL AGGLUTINATION TEST, COOMBS TEST, ENZYME-LINKED IMMUNOSORBANT ASSAY & PCR
* HIGH TITERS OF SPECIFIC IGG OR IGM
* BLOOD CULTURE & CSF , TISSUE, LYMPH NODE OR BONE MARROW CULTURE
* WBC COUNT - USUALLY NORMAL OR LOW WITH RELATIVE LYMPHOCYTOSIS
* THROMBOCYTOPENIA - MAY BE PRESENT
* BONE SCINTIGRAPHY - TO DETECT SPINAL OR EXTRASPINAL INVOLVEMENT
β’ Isolation of organism from blood, discharge, bone or
other tissue. Fastidious and slow-growing. Watch 3-4
weeks, with periodic subcultures. Automated systems
shorten time, but not all recognize brucellosis. PCR
accurate including non-blood samples, but not available
in most clinical labs. Skin tests not standardized, not
recommended for diagnosis.
β’ Acute illness: Blood culture is positive 70%, bone marrow
90%
β’ May have thrombopenia, disseminated intravascular
coagulation; granulopenia, lymphopenia, lymphocytosis.
30-60% with abnormal liver function test. Up to
70% may have normal labs.
β’ Serology: Brucella standard tube agglutination (STA)
paired sera, > 1:160 or 4 x rise (cheapest). Easy, accurate,
rapid dipstick for IgM now exists for developing
countries.
β’ More effective ELISA, indirect fl uorescent antibody test
(IFAT), Coombs tests, immunocapture-agglutination
(Brucellacapt). With ELISA, IgM, IgG or IGA may be
present at low levels > 1 year even if treated.
β’ IgM increased initially for several weeks, declines by 3
months
β’ IgG begins rise 2 weeks, may stay up (low levels) > 1
yr if treated or not treated (though IgM increase may be
lower or gone by 6 months if treated, can also persist >
1 year at low levels). IgG titer rises again with reinfection
or reactivation. IgG and IGA titer > 1:160 at 1 year
implies ongoing disease.
β’ New research: gene cloning and amplifi cation for
discriminatory markers detection and strain differences;
PCR-ELISA
IMAGING
β’ Bone scan, CT, depending on location
β’ Chest x-ray - pleural effusion, lung cavitation
β’ Joint x-rays frequently normal, requiring scan or MRI