Brucellosis

Brucellosis is a zoonotic bacterial infection caused by Brucella species, most commonly Brucella melitensis, Brucella abortus, Brucella suis, and Brucella canis. It affects a variety of animals and can be transmitted to humans, causing systemic illness that may become chronic if not treated.

Transmission occurs primarily through contact with infected animals or animal products, including unpasteurized dairy products, undercooked meat, or exposure to contaminated environments. Humans are usually infected through occupational exposure or consumption of contaminated foods. The incubation period typically ranges from one week to several months, with symptoms often developing gradually.

In humans, brucellosis presents with fever that may be undulating or relapsing, night sweats, fatigue, malaise, and musculoskeletal pains. Other manifestations can include hepatosplenomegaly, weight loss, and focal infections such as osteoarticular disease, endocarditis, meningitis, or neurobrucellosis. The disease can be challenging to diagnose due to nonspecific symptoms and overlap with other febrile illnesses.

Diagnosis relies on laboratory testing. Blood cultures or bone marrow cultures can detect Brucella, though cultures may be slow. Serologic tests (such as standard agglutination or ELISA) and, in some settings, PCR-based assays support diagnosis. Confirmation often requires a combination of clinical presentation and laboratory evidence.

Treatment involves combination antibiotic therapy for at least six weeks. A common regimen is doxycycline plus rifampin; alternative regimens include doxycycline with streptomycin or gentamicin. Chronic or focal brucellosis may require prolonged or additional therapies to prevent relapse.

Prevention focuses on controlling infection in animals and reducing human exposure. This includes pasteurization of dairy products, vaccination of livestock where available, surveillance and culling of infected herds, and the use of protective equipment for at-risk workers. Brucellosis remains a public health concern in regions with limited animal health infrastructure.