- Systemic granulomatous bacterial infection caused by Brucella sp. resulting in febrile illness; typically from ingestion of raw milk, unpasteurized milk, infected meat, or contact with secretions from infected animals
- One of the most common worldwide zoonotic diseases
- Incubation period usually 1 to 4 weeks but highly variable and may be several months
- Often presents insidiously with many atypical or nonspecific features
- Characterized by intermittent or irregular fevers and night sweats. Symptoms can range from subclinical disease to infection of almost any organ system.
- Bone and joint involvement is common—20–40% (typically spondylodiscitis).
- Disease may be recurrent, relapsing, or progress to chronic disease.
- System(s) affected: cardiovascular, endocrine/metabolic, gastrointestinal, musculoskeletal, nervous, pulmonary, renal/urologic, skin/exocrine
- Synonym(s): undulant fever; Malta fever; Mediterranean fever; Crimean fever; Bang disease
- May be mild or subclinical
- Boys infected more than girls (animal handling)
- Children often present with refusal to walk or bear weight.
- Children respond better to antibiotic treatment than do adults.
High rates of spontaneous abortion (can occur in subclinical cases). Early antibiotic treatment is preventive.
- Predominant age: 20 to 45 years (occupational exposure); sometimes children (milk-related outbreaks); can occur at all ages
- Predominant gender:
- Male > female (occupational exposure)
- Female ≥ male (milk exposure)
- >500,000 new cases yearly (likely underreported)
- <100 U.S. cases reported annually to the CDC
- Common in developing countries; highest in Turkey, Syria, and Iran; some countries report case rates as high as 10/100,000; present in all inhabited continents
- Highest rates in the United States are among Hispanic populations along U.S.–Mexico border; also Wyoming, North Carolina, Illinois, Florida, and Iowa
- Reportable in all states
Etiology and Pathophysiology
- Brucella ingestion from raw or undercooked tissue or unpasteurized milk products; susceptible to heat and disinfectant but can survive for weeks in frozen food and weeks to months in dust, soil, or water
- Facultative intracellular parasite: gram-negative, nonmotile, non–spore-forming coccobacillus
- Four species pathogenic to humans. Most virulent disease: Brucella melitensis, Brucella suis; also Brucella canis, Brucella abortus; can enter via mucous membrane or broken skin; occasionally inhaled
- Laboratory workers at high risk of infection if specimens handled improperly
- Person-to-person transmission is rare; sexual, vertical, (possibly) breast milk; blood transfusion
- Potential airborne biologic weapon
- Affects most domesticated ungulates (goats, cattle, camels, pigs, sheep), also wild bison and elk. Marine mammals also implicated in zoonotic transmission.
- Infection increases abortion rate in animals, less so in humans.
- Some evidence for intrauterine transmission; no reported birth defects
- Some complications may have genetic predisposition.
- In the United States, occupational exposure to infected animals (cattle and sheep): veterinarians, meat processors, accidental exposure to vaccine, lab technicians, recent immigrants
- Consumer exposure to unpasteurized dairy products and cheese
- Travel to endemic countries (Mediterranean, Middle East, North and East Africa, Central Asia, India, Mexico, Central and South America)
- Chronically ill and malnourished
- Potential acceleration of HIV disease
- Iron deficiency increases susceptibility.
- Bison and elk are infected with brucellosis near Yellowstone Park.
- Avoid infected, unpasteurized dairy products.
- Use caution handling animal vaccines. Use protective goggles and protective gloves when handling tissue.
- Human vaccine under investigation
- Postexposure prophylaxis same as treatment
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