Brucellosis
Brucellosis is a zoonotic infection from unpasteurized dairy, undercooked meat, or animal contact causing undulant fever, hepatosplenomegaly, arthralgia, and depression, diagnosed by extended-incubation blood or marrow culture and serum agglutination titer, and treated with doxycycline plus rifampin or gentamicin for six weeks.
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What this article covers
- Overview
A zoonotic, facultative intracellular infection caused by Brucella species, gram-negative aerobic coccobacilli that survive within macrophages of the reticuloendothelial system and can form noncaseating granulomas.
- Epidemiology
Highest prevalence in the Mediterranean countries, the Balkans, the Persian Gulf and Middle East, and Central and South America, reflecting regions with unpasteurized dairy consumption and close livestock contact.
- Risk factors
Consumption of unpasteurized milk, cheese, or other dairy products, the most common exposure worldwide.
- Pathophysiology
Brucella organisms are facultative intracellular pathogens that survive and replicate within macrophages of the reticuloendothelial system, evading humoral immune clearance and enabling the chronic, relapsing course.
- Clinical features
Undulant (waxing and waning) fever is the hallmark: intermittent fever with periods of remission lasting several weeks, or fever that may persist for months if untreated.
- Differential diagnosis
Q fever (Coxiella burnetii): Q fever Coxiella burnetii infection shares livestock/animal-product exposure but favors pneumonia and hepatitis with elevated transaminases; Brucella serology is negative.
- Diagnosis
Brucellosis is confirmed by isolating the organism in culture, or by a diagnostic serum agglutination titer: an initial titer of 1:160 or greater on the serum agglutination test, or a fourfold rise…
- Management
First, start combination therapy for uncomplicated brucellosis with doxycycline 100 mg PO twice daily for 6 weeks, plus one of the following, started concurrently with the first 2 to 3 weeks of…
- Complications
Endocarditis: the leading cause of brucellosis-related mortality, frequently culture-negative, often requiring combined prolonged antibiotics and valve surgery.
- Prognosis
Most uncomplicated cases respond to combination doxycycline-based therapy, though relapse can occur and warrants reassessment for an occult focal source rather than simple retreatment with the same regimen.
- Prevention
Avoid unpasteurized milk, cheese, and other dairy products, particularly when traveling in or emigrating from the Mediterranean, the Balkans, the Persian Gulf/Middle East, or Central and South America.
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