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Disease Categories > Infectious Disease > Bacteria

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Brucella

Brucellosis is a major bacterial zoonoses that involves many mammals including cows (B. abortus), pigs (B. suis), goats and sheep (B. melitensis), dogs (B. canis), and wild animals such as deer, elk and moose.

Epidemiology

Incidence – 1/100,000 in U.S.
Transmission
- A common route of Brucella infection is from eating or drinking infected, unpasteurized dairy products
- Infection can be via skin wounds
- Inhalation (majority are occupational exposure for this route)
- Vertical transmission via breast feeding

Organism

Brucella (gram-negative coccobacillus)
Facultative intracellular pathogen
Human infections are caused most frequently by B. melitensis, B. suis and B. abortus; rare infections are caused by B. canis

Risk Factors

Occupational or vocational exposure to animals
- Over 70% of reported cases occur in the meat-processing and livestock industries
- Brucella are able to penetrate intact skin so infections can result from simply handling infected animals

Clinical Presentation

Brucellosis in humans has a variable incubation time, an insidious or abrupt onset and no pathognomonic symptoms or signs
- Also called undulant fever
Following an incubation of 1-3 weeks, during which the organism resides in the lymph nodes, flu-like symptoms appear
- Constitutional – fever, chills, headache, weakness
- Osteoarticular – sacroiliitis, spondylitis, osteomyelitis
- Gastrointestinal – hepatomegaly (granulomatous hepatitis), splenomegaly
- Genitourinary – orchiepididymitis, glomerulonephritis, renal abscesses
- Neurologic – peripheral neuropathies, chorea, meningoencephalitis
- Mucocutaneous – purpura, maculopapular lesions, Stevens Johnson syndrome
- Pulmonary – pneumonia, pleural effusions
- Cardiovascular – endocarditis (aortic valve most common)
Chronic symptoms (recurrent fever, arthritis and fatigue) may also occur up to 1 year from illness onset

Diagnosis

Indications for testing – high level of suspicion based on occupation or travel history
Laboratory testing
- Serum antibodies by ELISA
  - Other antibody tests include agglutination tests which are less sensitive
- Gold standard – culture of tissue, blood or fluids
  - Organism is difficult to culture and very slow growing; may require weeks to grow

Differential Diagnosis

Malaria
Tuberculosis
Sepsis
Encephalitis
Tularemia
Bartonellosis
Syphilis

Treatment

Treatment is required and may be prolonged, and typically requires multiple antimicrobial agents
Relapse rate around 30%, even in compliant patients

Prevention

Control of disease in domestic livestock
Avoid unpasteurized milk and soft cheese produced from unpasteurized milk; especially goat cheese

Indications for Ordering

Tests generally appear in the order most useful for common clinical situations
Click on number for test-specific information in the ARUP Laboratory Test Directory

Test Name and Number	Recommended Use	Limitations
Brucella Antibodies, IgG & IgM 0050333 Method: Enzyme-Linked Immunosorbent Assay	Detect presence of Brucella antibodies in serum samples from patients with congruent clinical history	May not detect antibodies to B. canis Cross-reactions may occur between Brucella and F. tularensis antigens and antisera; parallel tests should be run with these antigens
Brucella Culture 0060159 Method: Standard reference procedures for Brucella culture and identification	Gold standard for detection of Brucella in blood (optimum), CSF, body fluids and abscesses	Serologic tests are generally used for the diagnosis of brucellosis because isolation of organism is difficult
Febrile Antibodies Panel 0051638 Method: Direct Agglutination/Enzyme-Linked Immunosorbent Assay/Immunofluorescence Assay	Use to confirm presence of disease; not recommended for initial testing Panel includes IgM Rickettsia rickettsii antibody by ELISA testing; as well as testing for antibodies to Brucella, Rickettsia typhi, Salmonella O and H	Initial testing may not be helpful; base treatment decision on clinical and other laboratory assessments

Additional Tests Available

Click on number for test-specific information in the ARUP Laboratory Test Directory

Test Name and Number	Comments
Brucella Antibody, IgG 0050334 Method: Enzyme-Linked Immunosorbent Assay
Brucella Antibody, IgM 0050336 Method: Enzyme-Linked Immunosorbent Assay
Brucella Antibody 0050135 Method: Bacterial Agglutination
Organism Identification by 16S rDNA Sequencing 0060720 Method: 16S rDNA Sequencing
Aerobic Organism Identification 0060115 Method: Standard reference procedures for aerobic bacterial identification and/or 16s rDNA sequencing for select bacterial isolates.
Aerobic Organism Identification with Reflex to Susceptibility 0065070 Method: Standard reference procedures for aerobic bacterial identification and/or 16s rDNA sequencing for select bacterial isolates and susceptibility tests.