Brucellosis: Technical Information

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Clinical Features

In the acute form (less than 8 weeks from illness onset), nonspecific and "flu-like" symptoms including fever, sweats, malaise, anorexia, headache, myalgia, and back pain. In the undulant form (less than 1 year from illness onset), symptoms include undulant fevers, arthritis, and epididymo-orchitis in males. Neurologic symptoms may occur acutely in up to 5% of cases. In the chronic form (more than 1 year from onset), symptoms may include chronic fatigue syndrome, depression, and arthritis.

Etiologic Agent

Brucella species, usually B. abortus (cattle), B. melitensis, B. ovis (sheep, and goats), B. suis (pigs), and rarely B. canis (dogs).

Incidence

In the United States, < 0.5 cases per 100,000 population, primarily B. melitensis. Most cases are reported from California, Florida, Texas, and Virginia.

Sequelae

Variable, including granulomatous hepatitis, peripheral arthritis, spondylitis, anemia, leukopenia, thrombocytopenia, meningitis, uveitis, optic neuritis, papilledema, and endocarditis.

Transmission

Zoonotic. Commonly transmitted through abrasions of the skin from handling infected mammals. In the United States, occurs more frequently by ingesting unpasteurized milk or dairy products. Highly infectious in the laboratory via aerosolization; handling cultures warrants biosafety level-3 precautions.

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Risk Groups

Abattoir workers, meat inspectors, animal handlers, veterinarians, and laboratorians.

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Surveillance

Brucellosis is a nationally notifiable disease and reportable to the local health authority.

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Trends

For previous 10 years, approximately 100 cases per year have been reported.

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Challenges

Elimination of domestic and feral animal reservoirs. In 2001, the National Brucellosis Eradication Program reported only 3 newly affected cattle herds, compared to 14 herds identified in 2000. Establish and validate methods for isolation and detection of Brucella spp. in foods.

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